w & GASEOUS EXCHANGE AND PHYSIOLOGICAL REQUIREMENTS FOR LEVEL AND GRADE WALKING BY HENRY MONMOUTH SMITH PUBLISHED BY THE CARNEGIE INSTITUTION OF WASHINGTON WASHINGTON. APRIL, 1922 GASEOUS EXCHANGE AND PHYSIOLOGICAL REQUIREMENTS FOR LEVEL AND GRADE WALKING BY HENRY MONMOUTH SMITH PUBLISHED BY THE CARNEGIE INSTITUTION OF WASHINGTON WASHINGTON, APRIL, 1922 CARNEGIE INSTITUTION OF WASHINGTON PUBLICATION No. 309 PRESS OF GIBSON BROTHERS WASHINGTON S7 PREFACE. The following report presents the results of a series of experiments carried out in continuation of a plan of study at the Nutrition Labora- tory on the energy expenditure during muscular work, and supple- ments the report of Benedict and Murschhauser: Energy Transforma- tions during Horizontal Walking. The author is indebted to the Director, Dr. Francis G. Benedict, for his constant interest and criticism as the work progressed, and to Miss A. N. Darling for her painstaking supervision of the editorial work in preparing the material for publication. He is also indebted to Mr. Karl H. Brown for his interest and fidelity in the difficult task of recording the pulse-rates and to Mr. William H. Leslie for much of the labor involved in the calculations, and preparation of the tables. NUTRITION LABORATORY OF THE CARNEGIE INSTITUTION OF WASHINGTON, Boston, Massachusetts, April 23, 1921. CONTENTS. PAGE. Introduction 1 Researches by other investigators on energy requirements for walking 3 Horizontal walking 3 General considerations with regard to previous researches on horizontal walking 7 Grade walking 8 General considerations with regard to previous work on grade walking. ... 15 Plan of study 16 Methods of measurement 18 Universal respiration apparatus 20 Tests of the universal respiration apparatus 25 Treadmill 27 Measurement of the step-lif t 30 Method of step-counting 33 Apparatus for determining the pulse-rate 33 Oscillograph 34 Cambridge string galvanometer 34 Electrodes 35 Technique for securing records of the pulse-rate 36 Determination of the body-temperature 36 Determination of the blood-pressure 37 Routine of experiments 38 Subjects 41 Statistics of experiments 42 Discussion of results 90 Basal metabolism 90 Experiments with subject standing 94 Metabolism during standing 94 Carbon-dioxide elimination 94 Oxygen consumption 95 Respiratory quotient 95 Heat-output 96 General summary of measurements of metabolism during standing ... 97 Comparison of metabolism for lying and standing positions 100 Physiological effects of standing 101 Respiration-rate with subject standing 101 Pulmonary ventilation with subject standing 103 Pulse-rate with subject standing 106 Rectal body-temperature with subject standing 113 BJood-pressure with subject standing 115 Experiments with horizontal walking 116 Metabolism of subjects while walking on a level 116 Total metabolism during horizontal walking 116 Increment in metabolism due to horizontal walking 120 Total increment in heat-production 139 Increment in heat per horizontal kilogrammeter 139 Effect of speed upon metabolism in horizontal walking 143 Effect of speed upon total heat-output 145 Effect of speed upon total increase in heat-output 146 Effect of speed upon increase in heat per horizontal kilogrammeter. . . 147 Experiments with subject "marking time" 150 Steps and step-lift during horizontal walking 152 Number of steps in horizontal walking 154 Step-lift during horizontal walking 155 Possible causes for variation in step-lift 155 Total step-lif t per minute 156 Step-lift per step 157 Energy increment due to work of step-lift 157 Vi CONTENTS. PAGE. Discussion of results continued. Experiments with horizontal walking continued. Physiological effects of horizontal walking 160 Respiration-rate during horizontal walking 160 Pulmonary ventilation during horizontal walking 162 Pulse-rate during horizontal walking 163 Comparison of pulse-rate during standing with that during horizontal walking 165 Relationship of oxygen consumption, pulse-rate, and pulmonary ven- tilation during horizontal walking 169 Body-temperature during horizontal walking 172 Blood-pressure during horizontal walking 175 Experiments with grade walking Physiology of mouth-breathing appliances 177 Effect of mouthpiece breathing upon metabolism 178 Effect of mouthpiece breathing upon respiration-rate, pulmonary ven- tilation, and rate of oxygen consumption 182 Effect with subject standing 184 Effect during grade walking 184 Conclusions with regard to the effect of long and short preliminary mouthpiece breathing 192 Metabolism of subjects walking on an incline 193 Carbon-dioxide elimination and oxygen consumption during grade walking 224 Respiratory quotient during grade walking 230 Total heat-output during grade walking 233 Increment in heat-output due to grade-lift 238 Total increment in heat due to grade-lift 238 Increment in heat per kilogrammeter of work done in grade-lift. . 241 Step-lift during grade walking 243 Comparison of step-lift in horizontal and grade walking 246 Work of ascent 248 Efficiency in grade walking 249 Efficiency in work due to grade-lift '. 249 Efficiency in work of ascent 253 Effect of lameness upon the efficiency of E. D. B 256 Physiological effects of grade walking 257 Respiration-rate during grade walking 257 Pulmonary ventilation during grade walking 260 Pulse-rate during grade walking 262 Body-temperature during grade walking 268 Blood-pressure during grade walking 276 Physiological changes in transition from standing to grade walking and the reverse 277 Respiratory changes in transition from standing to grade walking 278 Changes in respiration-rate 279 Changes in pulmonary ventilation 284 Changes in rate of oxygen consumption (unreduced) 284 Respiratory changes in transition from grade walking to standing .... 287 Changes in respiration-rate 288 Changes in pulmonary ventilation 293 Changes in rate of oxygen consumption (unreduced) 295 Conclusions regarding respiratory changes in transition from grade walking to standing and the reverse 296 Pulse-rate in transition from standing to grade walking 297 Pulse-rate in transition from grade walking to standing 303 After-effects of grade walking 305 Summary of results 309 ILLUSTRATIONS. PAGE. FRONTISPIECE. Subject and apparatus in readiness for experiment. Fio. 1. Treadmill, with spirometer and various recording devices 19 2. Double spirometer 22 3. Respiration counter 24 4. Electrical counter for recording number of respirations 24 5. Detail of valve-operating device and period counter 28 6. Framework used in determining the angle of ascent , 29 7. Step-lift recorder 30 8. Typical records of pulse-rate as obtained with oscillograph and string gal- vanometer 34 9. Metabolism of E. D. B. in standing experiments without food 98 10. Increments in total heat-output over standing requirement for subjects walking on a level at different rates in meters per minute, with per- centage increase for E. D. B 146 11. Average energy cost per horizontal kilogrammeter of walking on a level at various distances per minute 148 12. Typical pulse-rate curves for E. D. B. and W. K. during standing and hori- zontal-walking experiments 166 13. Total heat-output, oxygen consumption, pulmonary ventilation, respira- tion-rate, and pulse-rate of E. D. B. and W. K., referred to hori- zontal kilogrammeters for experiments with subjects walking on a level at different speeds 170 14. Typical body-temperature curves for E. D. B. during periods of standing and periods of walking on a level at various speeds 173 15. Reproduction of kymograph records in mouthpiece experiments, with intermittent renewal of oxygen 183 16. Total carbon-dioxide production of T. H. H., H. R. R., and W. K., re- ferred to kilogrammeters of work performed in walking on different grades 225 17. Total carbon-dioxide production of E. D. B. referred to kilogrammeters of work performed in walking on different grades 226 18. Total oxygen consumption of T. H. H., H. R. R., and W. K. referred to kilo- grammeters of work performed in walking on different grades 227 19. Total oxygen consumption of E. D. B. referred to kilogrammeters of work performed in walking on different grades 227 20. Respiratory quotients of W. K. and E. D. B. referred to kilogrammeters of work performed in grade walking 230 21. Total heat-output of W. K. referred to kilogrammeters of work performed in walking on different grades 234 22. Total heat-output of E. D. B. referred to kilogrammeters of work performed in walking on different grades 234 23. Total oxygen consumption and heat-production of W. K. referred to kilo- grammeters of work performed in grade walking 236 24. Total oxygen consumption and heat-production of E. D. B. referred to kilogrammeters of work performed in grade walking 237 25. Daily increments in heat-production over standing requirement and hori- zontal component referred to kilogrammeters of work done in walking experiments on different grades with W. K 239 26. Daily increments in heat-production over standing requirement and hori- zontal component referred to kilogrammeters of work done in walking experiments on different grades with E. D. B 239 27. Average increments in heat-production due to grade-lift in walking experi- ments with E. D. B 240 vii Vlll ILLUSTRATIONS. PAGE. FIG. 28. Pulse-rate, respiration-rate, and pulmonary ventilation of W. K. during grade walking, referred to kilogrammeters of work 258 29. Pulse-rate, respiration-rate, and pulmonary ventilation of E. D. B. during grade walking referred to kilogrammeters of work 259 30. Typical pulse curves of E. D. B., with subject standing, walking on a level, and walking on an incline 265 31. Typical pulse curves of E. D. B., with subject standing and walking on an incline 266 32. Typical pulse curves of E. D. B., with subject standing and walking on an incline 267 33. Typical body-temperature curves of E. D. B., with subject standing and walking on an incline 269 34. Typical body-temperature curves of E. D. B., with subject standing and walking on an incline 271 35. Typical body-temperature curves of E. D. B., with subject standing and walking on an incline 272 36. Typical body-temperature curves of E. D. B., with subject standing and walking on an incline 274 37. Contrasting curves of body-temperature of E. D. B., with subject standing and walking on an incline 275 38. Typical kymograph records of respiration, pulmonary ventilation, and rate of oxygen consumption in periods of transition from standing to walk- ing and the reverse 278 39. Duration of pulse-cycles of E. D. B., in transition from standing to grade walking, as indicated by average cycle duration for measured groups of 10 pulse-cycles 298 40. Duration of pulse-cycles of E. D. B., in grade-walking experiment of Feb- ruary 28, 1916, as indicated by averages of 2 pulse-cycles, measured individually 300 41. Duration of pulse-cycles of E. D. B., in grade-walking experiment of Feb- ruary 29, 1916, as indicated by averages of 2 pulse-cycles, measured individually 301 42. Duration of pulse-cycles of E. D. B. in transition from grade-walking to standing, as indicated by average cycle duration for measured groups of 10 pulse-cycles 304 GASEOUS EXCHANGE AND PHYSIOLOGICAL KE- QUIEEMENTS FOE LEVEL AND GRADE WALKING INTRODUCTION. This investigation was undertaken as a part of the larger plan formulated in the Nutrition Laboratory some years ago for the study of the energy requirements of the body during muscular exercise, including a consideration of the efficiency with which the human body can perform some of its more common daily tasks. The results of Atwater and Benedict, 1 obtained in experiments with the respiration calorimeter at Wesleyan University, demonstrated that the energy of the human body could be measured like that of any machine. Accordingly, when the Nutrition Laboratory was established in Boston, the plans for research included a continuation of this work, and a res- piration calorimeter was constructed, which was designed especially for this type of experiment. The results of the studies of Zuntz 2 and his associates on the gaseous exchange of the animal body demonstrate that the energy require- ments can be found indirectly by computation from the oxygen con- sumption and the respiratory quotient with an expenditure of much less time and effort than is required for direct measurements by the respiration calorimeter. This has resulted in a diminishing use of the respiration calorimeter for the energy measurements of the human body, and the data reported in the following pages have been obtained by indirect calorimetry. However, it must not be overlooked that the respiratioti calorimeter first demonstrated that the law of the conservation of energy holds in the animal body and that for our knowledge of the values used in indirect calorimetry we depend on data obtained by direct calorimetric measurements. The numerous comparisons of direct and indirect calorimetry made by Lusk and Du Bois in New York, with the calorimeter at the Russell Sage Institute of Pathology, as well as those made with the calorimeters at Wesleyan University and later at the Nutrition Labora- tory, have shown that with severe muscular work the agreement between the results obtained by the direct and indirect methods is 'Atwater and Benedict, U. S. Dept. Agr., Office Exp. Sta. Bull. 69, 1899; ibid, Bull. 109, 1902; ibid, Bull. 136, 1903; Benedict and Milner, U. S. Dept. Agr., Office Exp. Sta. Bull. 175, 1907; Benedict and Carpenter, U. S. Dept. Agr., Office Exp. Sta. Bull. 208, 1909. J Zuntz, Archiv f. d. ges. Physiol., 1897, 68, p. 201. See, also, Zuntz and Schumburg, Physi- ologic des Marsches, Berlin, 1901, p. 260. 2 METABOLISM DURING WALKING. ideal for periods of 24 hours. During rest experiments the agreement has been shown to obtain for periods as short as one hour. The agree- ment in the short periods has not, however, been thus far demonstrated under conditions of excessive muscular work with accompanying alterations in body-temperature and the possibility of over-ventilation of the lungs, as well as possibilities of special metabolic cleavages, such as lactic acid. In the research here projected it was definitely planned to conduct the experiments ultimately in a respiration chamber provided with calorimetric features. Since special stress was to be laid upon the measurements of ventilation of the lungs, body-temperature, heart- rate, and physiological factors other than the metabolism, it was deemed wisest first to carry out a series of experiments in which the subject walked upon a treadmill in the laboratory and was thus much more accessible than he would be when walking upon a treadmill in a respiration chamber. It is this series of experiments that is reported in this publication. The calorimeter for carrying out the work experi- ments planned has actually been constructed in the Nutrition Labora- tory and thoroughly tested as to its capacity for measuring large amounts of heat as well as respiratory products. At the moment of writing it has not been used for experiments with men on the treadmill. It is hoped that when full information is obtained of some of the fundamental requirements of the human body during periods of muscular exercise, scientists will be in a better position to consider the question from the standpoint of industrial efficiency, and that in the end it may be possible to state whether or not a laborer should be able to perform a given amount of work with a greater efficiency than is commonly done, that is, with less cost to the body economy. If such evidence is positive, the problem of training the laborer and determining in what way the energy is wasted will be the next and most obvious step, and the suggestions and criticisms of Frederick W. Taylor 1 would have the added support of physiological science. Mention should also be made here of the very clever mechanical devices of Amar, 2 who has already attacked the problem of efficiency in various kinds of work. The results of two researches 3 made by this Laboratory as a part of the original plan have already appeared. The following pages present the results of further study which has been applied more especially to the work of grade walking. As a necessary accompaniment of a study of grade walking, observations were made with the subject 1 Taylor, The principles of scientific management, New York, 1911. 1 Amar, Le moteur humain, Paris, 1914. 3 Benedict and Cathcart, Carnegie Inst. Wash. Pub. No. 187, 1913; Benedict and Mursch- hauser, Carnegie Inst. Wash. Pub. No. 231, 1915. RESEARCHES BY OTHER INVESTIGATORS. 3 walking on a level. These served the dual purpose of (a) supplying a suitable base-line for the proper study of the special factors involved in grade walking, and (6) supplementing to a not inconsiderable extent the present knowledge regarding the physiology of horizontal walking. Additional data have been collected on the changes in the pulse-rate, respiration-rate, the pulmonary ventilation, and body- temperature as affected by the intensity of the work in both horizontal and grade walking, and their relation to the energy expended. RESEARCHES BY OTHER INVESTIGATORS ON ENERGY REQUIREMENTS FOR WALKING. HORIZONTAL WALKING. The earlier studies of the energy metabolism during horizontal walking have been reviewed by Durig 1 and by Benedict and Mursch- hauser. 2 One of the main subjects of interest in this work is the determination of the energy cost per horizontal kilogramme ter, i. e., the energy cost of the movement of 1 kilogram 1 meter in a horizontal direction. The earlier studies were made under various conditions of rest, food, altitude, speed of walking, and methods of computation as regards the basal value. In consequence, the results vary widely, Benedict and Murschhauser in their summary table noting average values ranging from 0.308 to 1.169 gram-calories per horizontal kilo- grammeter. Durig showed that when the rate of walking was limited to moderate speeds and the subject was in the post-absorptive condi- tion, the energy expenditure was very close to 0.55 gram-calorie per horizontal kilogrammeter, but when the speed exceeded a certain degree, given by Durig as approximately 80 meters per minute, the energy cost per horizontal kilogrammeter increased. This limiting speed Durig' termed the "maximal economic velocity." Reichel, 3 in Durig's laboratory, gave a mathematical formula to this generalization, and Durig further states that for each meter in excess of the maximal economic velocity, the energy metabolized increases from 1.2 to 1.5 per cent of the normal value. In continuation of Durig's work and employing his well-established methods, Brezina and Kolmer 4 conducted experiments on horizontal walking with and without load at varying velocities. In these studies the authors confirmed the results of Durig in relation to the absence of the effects of speed below the maximal economic velocity, and add that this value is independent of a load up to 21 kg., that is, a dead rig, Denkschr. d. math.-natur. Klasse d. kaiserl. Akad. d. Wissensch., 1909, 86, p. 250. 2 Benedict and Murschhauser, Carnegie Inst. Wash. Pub. No. 231, 1915. 3 See Durig, Denkschr. d. math.-natur. Klasse d. kaiserl. Akad. d. Wissensch., 1909, 86, pp. 278 and 279. 4 Brezina and Kolmer, Biochem. Zeitschr., 1912, 38, p. 129. 4 METABOLISM DURING WALKING. load of 21 kg. can be carried by the human body as economically as the same amount of live weight. Above either this load or the maximal economic velocity the energy metabolized per horizontal kilogram- meter increases. These authors further state that if a definite weight is to be transported it can be accomplished more economically by increasing the load than by increasing the velocity. As all these ob- servations were made on but one subject (Brezina), the physiologically interesting problem as to the application of these general deductions to persons of widely differing weights remains to be settled. , Subsequently, Brezina and Reichel 1 made a study of these data of Brezina and Kolmer in an endeavor to express the relations between the increase in metabolism and the increase in load and in velocity. They give the results of their treatment of the data in the form of two generalizations, (a) that for moderate speeds the cost of 1 h. kg. m. is independent of the speed and is smallest for loads of approximately 19 kg., and (6) that the energy increase for loads above this maximum weight of 19 kg. is proportional to the square of the load difference. (L 19) 2 Expressed in terms of calories, the equation is C7=0.5H , in 10,000 which U equals calories per horizontal kilogrammeter and L equals load in kilograms. Beyond the point of maximal economic velocity, the metabolism increases per horizontal kilogrammeter in geometrical ratio to the arithmetical increase in the speed. Benedict and Murschhauser 2 for their two subjects found the energy requirement per horizontal kilogrammeter to be 0.507 and 0.493 gram-calorie, respectively, for speeds of approximately 75 meters per minute, that the energy requirements increased with the increase in speed, and that running at 147.5 meters per minute was more economi- cal than walking at the same velocity. A measurement of the energy required for the elevation of the body due to the step-movement showed that, with a speed of 76 meters per minute, one of their sub- jects, weighing 73 kg., expended 0.65 calorie in this work, that is, 23 per cent of the increase in metabolism over the standing requirements was due to this work of step-elevation. Waller, 3 in a series of reports on the physiological cost of various forms of muscular work, included a few experiments on horizontal walking. Computations show that his results for speeds of approxi- mately 100 meters per minute yield somewhat over 0.8 gram-calorie per horizontal kilogrammeter. Running at a speed of approximately 200 meters per minute gave a heat-production of about 1.3 gram- calories per horizontal kilogrammeter. The first value is measurably Brezina and Reichel, Biochem. Zeitschr., 1914, 63, p. 170. 2 Benedict and Murschhauser, Carnegie Inst. Wash. Pub. No. 231, 1915, pp. 79 and 87. 3 Waller, Journ. Physiol., 1919, 53, Proc. Physiol. Soc., p. xxiv; see, also, Journ. Physiol., 1919, 52, Proc. Physiol. Soc., p. Ixxii. RESEARCHES BY OTHER INVESTIGATORS. 5 higher than that usually found, and may in part be explained by the fact that, as Waller himself states, his method determines only the carbon-dioxide production, a respiratory quotient is assumed, and there is an acknowledged error of 5 per cent. In general, his values run somewhat higher than those commonly accepted as a result of other walking experiments. Benedict, Miles, Roth, and Smith, 1 in the report of a study on the effects of restricted diet, include the measurement of the gaseous exchange during level walking on a treadmill of a group of 12 young men in normal condition and of the same group after 20 days of re- stricted diet. They likewise report the gaseous exchange during walking of a group of 1 1 men after they had been on a restricted diet for a period of 120 days. A special closed-chamber method was used, and the carbon dioxide produced and the oxygen consumed were determined by analysis of the chamber air. They found the average cost per horizontal kilogrammeter for the normal men to be 0.597 gram-calorie, and for the same group after 20 days of restricted diet 0.562 gram- calorie. For the group with a restricted diet for 120 days the cost per horizontal kilogrammeter was 0.522 gram-calorie, thus indicating a somewhat greater efficiency per unit of work for the men who were on a restricted diet and much below then* usual body-weight. These figures, the authors state, were for brief periods of moderate speed (70 meters per minute) and do not apply to conditions in which con- tinued exercise and stamina might be prime requisites. Cathcart and Orr, 2 using the Douglas bag method, made a series of studies on the energy requirements for the various forms of exercise required of British recruits. Inasmuch as the experiments were carried out under various conditions of weather and terrain, the authors distinctly state that all they could expect to obtain was an average of the energy expended in performing any given type of drill. Among the many forms of exercise reported in their publication was included that of marching with light (15.3 kg.), medium (20.5 kg.), and heavy (25 kg.) loads. The speed was 91.4 meters per minute on a comparatively level and smooth stretch of road. For these con- ditions they found the cost per horizontal kilogrammeter to be 0.543, 0.638, and 0.672 gram-calorie for the several loads. In addition to these field tests, a series was also made on one of the authors wherein the details are more nearly those of the laboratory research in which the effects of diet and the effects of velocity and load were studied. Under these conditions they found an increased cost per horizontal kilogrammeter with increase in speed and load from approximately 0.52 gram-calorie for a speed of 57 meters per minute to 0.85 gram- Benedict, Miles, Roth, and Smith, Carnegie Inst. Wash. Pub. No. 280, 1919, p. 546. 2 Cathcart and Orr, The energy expenditure of the infantry recruit in training. H. M. Stationery Office, London, 1919. 6 METABOLISM DURING WALKING. calorie at a speed of 183 meters per minute with a load of 11 kg., and from 0.48 to 0.72 gram-calorie with a load of 26 kg. The last value was, however, for a speed of 110 meters per minute. They also found the average cost per horizontal kilogrammeter for three subjects walking with a 9 kg. load at speeds of 55, 82, and 110 meters per minute to be 0.48, 0.51, and 0.65 gram-calorie. Liljestrand and Stenstrom 1 report a series of respiration experiments with the subjects either walking or running. These authors used the Douglas bag, with the men in the post-absorptive condition. The walking was done on a level track of oval form in the vStadium a: Stockholm. The distances walked were 100 meters, with a preliminary period of 1 minute or longer. Measurements for both the sitting and standing positions were also made. The investigators report their values as oxygen consumed per horizontal kilogrammeter. After deducting a resting value for sitting, they assumed a respiratory quo- tient and calculated for the subject N. S. (body-weight 80 kg.) an average cost per horizontal kilogrammeter of 0.517 gram-calorie for walking at a speed of 50 to 75 meters a minute. For a speed of 75 to 100 meters per minute the cost was 0.613 gram-calorie, and above 100 meters per minute it was 0.830 gram-calorie. For the subject G. L. (body-weight, 60 kg.) the energy cost at similar speeds was 0.491, 0.574, and 0.710 gram-calorie, respectively. In their experiments with the subject running these authors found that the cost per horizontal kilogrammeter fell with the increase in speed. For the subject N. S., with a speed of from 144 to 175 meters per minute, the heat expenditure was 1.004 gram-calories per hori- zontal kilogrammeter. This fell to 0.796 gram-calorie for a speed between 225 and 250 meters per minute. Similar results were found with the subjects G. L. and E. S. Cathcart, Lothian, and Greenwood 2 have considered the energy expended in relation to the velocity of walking and take exceptions to the generalization of Brezina and Reichel that the cost of movement remained constant up to a velocity of 80 meters per minute and there- after increased geometrically. They contend that as a general physio- logical law it involves a discontinuity at a fixed point between the speed and the energy expenditure, and other evidence points to uneconomical work at low speeds. Furthermore, as an interpolation formula, they consider the data upon which it is based are insufficient, for although they cover a wide range of speed and load, they relate to but one subject. These authors, using the data of Brezina and Reichel, show that the relation between the energy cost per unit of time and speed may be represented with equally good approximations to the 'Liljestrand and Stenstrom, Skand. Archiv f. Physiol., 1920, 39, p. 167. *Cathcart, Lothian, and Greenwood, Journ. Roy. Army Med. Corps, April, 1920. RESEARCHES BY OTHER INVESTIGATORS. 7 observed values by a formula differing from that of Brezina and Reichel. They conclude that neither their own formula nor that of Brezina and Reichel expresses a physiological law and that they are useful solely as interpolation formulae. They also find that by applying their equation to some 150 experiments made at speeds of 55, 82, and 110 meters per minute, the optimum rate of walking was approximately 82 meters per minute, a value close to that found by Durig. GENERAL CONSIDERATIONS WITH REGARD TO PREVIOUS RESEARCHES ON HORIZONTAL WALKING. From the large mass of evidence obtained in European and American laboratories on the metabolism during horizontal walking, it can be seen that no little portion of it has been accumulated with the primary object of the transportation of loads. This has in part been neces- sitated by the technique employed in the Zuntz school of carrying on the back a rather cumbersome and weighty meter with its attach- ments, and in part by the fact that interest has been stimulated by Alpine touring. Certain fundamental experiments have been made in laboratories by means of treadmills. When a pack was not trans- ported the results of these earlier experiments are perfectly comparable with those with free walking. They are, however, even at best, too few, and accumulation of further evidence is entirely justified. Practically all of the results point towards the excellence of the work carried out under the supervision of Durig. Inherently, per- haps, no further investigation on horizontal walking per se is justifiable with the great number of other problems on walking which await solution. Durig's main problem was the study of the metabolism for the work of ascent, but unfortunately nearly all of his work included not only the transportation of a load but the use of a cumbersome, unweildy gas-meter carried on the back. That these conditions do not call into play a much larger degree of muscular coordination than would ordinarily be required in free walking is difficult to believe. On the other hand, it is clear that Durig's values for the energy required to transport 1 kg. a horizontal meter are closely in accord with the results of practically all the work done by other methods, although, as a rule, they run slightly higher, which would be expected from the nature of the technique. Two important points must be considered: First, that for all investi- gations on grade walking, clearly established base-lines are necessary. These can best be obtained by actual test, i. e., by having the subject walk on a horizontal plane under exactly the same conditions as he sub- sequently walks on a grade. This particular factor influences in large part the accumulation of the material on horizontal walking to be given in the present report. Secondly, evidence has been forthcoming, although unfortunately 8 METABOLISM DURING WALKING. as yet not accompanied by clearly defined experimental proof, that walking in free, open air has a measurably different physiological effect from that of. walking on a treadmill in a more or less closed laboratory. In any event, this effect must be relatively small in degree as compared to the effect of grade walking. Consequently, all contributions to technique or to the physiology of horizontal walking that will make the establishment of the normal base-line more definite are to be welcomed, for the problem of the difference in effect of walking in the open air as compared to walking on a treadmill in a well-venti- lated room can only be solved by the use of impeccable technique. GRADE WALKING. The majority of the studies which involve grade walking have been made in connection with studies of the effects of high altitudes upon the physiological actions of the human organism. The conditions of high altitudes, mountain paths, and, in many cases, a previous diet, must be taken into consideration in examining the results. In prepara- tion for these mountain expeditions, nearly all the researches included a series of treadmill experiments which alone are really comparable with our results. Most of the results in these experiments were obtained by the Zuntz method. With this method the subject breathes through suitable valves, the volume of air is measured, and its composition determined by analysis of carefully drawn samples. From the known heat value of a cubic centimeter of oxygen or carbon dioxide for the respiratory quotient found, the energy expended per unit of tune is then calculated. The basis for comparison was the carbon-dioxide production, the oxygen consumption, or the heat expended per kilogrammeter of work done by the subject in lifting his body-weight, plus any loads he carried in the form of equipment, such as gas-meter, etc., to the elevation attained by the grade, or briefly, the work of the "grade-lift." The question of the proper base-line has been variously treated. The resting or maintenance metabolism in either the lying or the standing position has been universally deducted from the total gaseous exchange measured, but the allowance for the so-called "horizontal component" has been variously regarded. It is more generally estimated as equivalent to an equal linear distance found from horizontal-walking experiments. In other cases, no allowance has been made for this factor, but the energy expended per meter of distance walked and kilogrammeter of lift is reported. In 1891, Katzenstein 1 made some measurements of the gaseous metabolism during grade walking in the laboratory of Zuntz in Barlin, employing a treadmill and the Zuntz method of measuring the gaseous Katzenstein, Arch. f. d. ges. Physiol., 1891, 49, p. 330. RESEARCHES BY OTHER INVESTIGATORS. 9 exchange. Four subjects were used and the basal metabolism and the metabolism during horizontal walking were determined. The grade of the treadmill was of moderate pitch, varying from approximately 10 to 13 per cent. As computed from the respiratory quotients, the heat-output was 5.69 to 7.33 calories per kilogrammeter, with efficien- cies of 31.9 to 41.1 per cent. The great variations in the results of Katzenstein are in no small part due to the wide differences in his estimations of the oxygen consumption per horizontal kilogrammeter, which ranged from 0.0858 c. c. for his subject Zimm to 0.1682 c. c. for his subject Krzywy, and also to the fact that the relatively low grade of the treadmill did not produce a large amount of work. In the same year Gruber 1 made a study of the effect of training in the ascent of approximately 80 meters to the Minister tower outside of Berne. The experiments were made after a midday meal, and the carbon-dioxide production alone was determined by a gravimetric method. The results are primarily of interest as implying increased efficiency following training. Schumburg and Zuntz, 2 in a study of the effects of high altitudes, report a series of experiments with Zuntz walking on a treadmill in Berlin at a grade of 31 per cent and a speed of 24 meters per minute, in which the average oxygen consumption per kilogrammeter of work done was 1.77 c. c., or an efficiency of 27 per cent. With Schumburg as the subject, the oxygen consumption was 1.73 c. c., with an efficiency of 28 per cent. Later, these two men, when walking up a grade of 31 per cent on Monte Rosa, found their efficiencies to be 20.9 and 23.2 per cent. A. and J. Loewy and L. Zuntz, 3 preliminary to their expedition to Monte Rosa, made a series of measurements on a treadmill in Berlin at grades of about 23.0, 30.5, and 36.6 per cent. The energy produc- tion per kilogrammeter of grade work, after the resting value and the value for the horizontal component had been deducted, varied from 6.74 to 8.07 calories per kilogrammeter for A. L., 6.53 to 7.30 calories for J. L., and 6.41 to 7.32 calories for L. Z., with efficiencies from 29 to 36.5 per cent. The lowest efficiency was found with A. L. and the highest with L. Z. In the expedition on Monte Rosa made by these investigators, in walking up grades of 26 to 33 per cent at Col d'Olen with an elevation of 2,840 meters, and at Capanna Gnifetti, with an elevation of 3,620 meters, the metabolism per kilogrammeter of work due to the grade walking was as follows: For A. L., 8.13 and 9.11 calories per kilograms meter; for J. L., 8.23 and 8.99 calories; for L. Z., 8.77 and 8.41 calories. The efficiencies were: For A. L., 28.8 per cent at Col d'Olen, and 25.7 Gruber, Zeitschr. f. Biol., 1891, 28, p. 466. 2 Schumburg and Zuntz, Arch. f. d. ges. Physiol., 1896, 63, p. 461. 3 A. and J. Loewy and L. Zuntz, Arch. f. d. ges. Physiol., 1897, 66, p. 477. 10 METABOLISM DURING WALKING. per cent at Capanna Gnifetti; for J. L., 28.4, and 26.0 per cent; and. for L. Z., 26.7 and 27.8 per cent, respectively. Biirgi, 1 in a study on the effects of training, made ascents of 25 per cent grade at Brienz (734 meters) and the Rothqrn (2,184 meters); also on the Gornergrat, where the grade was 19.3 per cent and the height 2,987 meters. The carbon dioxide only was determined in these experiments. From Biirgi's results, Durig 2 has computed the energy required per kilogrammeter of grade work, using an assumed respiratory quotient of 0.80, and found it to be 8.6 to 9.8 calories at Brienz, 10.2 to 12.3 calories on the Rothorn, and 9.3 calories on the Gornergrat. After training the expenditures were lower. Frentzel and Reach, 3 in their study on the source of muscular power reported some experiments in which the subject walked on the tread- mill with a grade of 23 per cent. These experiments, however, were not made with the man in the post-absorptive condition, but after a special diet of carbohydrates, proteins, or fats. From the data for the gaseous exchange the computed efficiencies are 36.4 for F. and 35 per cent for R. Zuntz and Schumburg, 4 in their comprehensive study of marching, included a few experiments on grade walking. These, however, were made with a grade of only 6.5 per cent. We have computed an effi- ciency from their data of 31.2 per cent. Durig and Zuntz 5 give the energy expended by themselves when walking on the glacier of Monte Rosa as 14.65 and 9.76 calories per kilogrammeter of work. The low efficiencies are obviously attribut- able to the poor footing. Durig, 6 in 1906, made some grade studies upon himself 1| to 2 hours after a light breakfast, when walking with a load of 18 kg. on the Bilkengrat at grades of 25 to 27 per cent. In all, 33 experiments were reported, showing an efficiency of 25.6 to 29.8 per cent. The average expenditure was 7.9 calories and the average efficiency 29.S per cent. Durig found that the efficiency increased with practice^ He also found a greater metabolism in the first periods of the day, indicating need of practice for each day, that the path conditions had little effect, and that the respiratory quotient had a tendency to fall. In 1901, Zuntz and his colleagues, A. Loewy, M tiller, and Caspari, 7 spent the summer upon Monte Rosa, where elaborate studies were 'Biirgi, Arch. f. Anat. u. Physiol., Physiol. Abth., 1900, p. 509. l Durig, Denkschr. d. math.-natur. Klasse d. kaiserl. Akad. d. Wissensch., 1909, 86, p. 300. 'Frentzel and Reach, Arch. f. d. ges. Physiol., 1901, 83, p. 477. 4 Zuntz and Schumburg, Physiologic des Marsches, Berlin, 1901. "Durig and Zuntz, Travauz de 1'annee 1903, Laboratoire scientifique international du Mont Rosa, Turin, 1904, p. 65; also Arch. Anat. u. Physiol., Physiol. Abth., 1904, Suppbd., p. 417. *Durig, Arch. f. d. ges. Physiol., 1906, 113, p. 213. 7 Zuntz, Loewy, Miiller, and Caspari, Hohenklima u. Bergwanderungen, Berlin, 1906. RESEARCHES BY OTHER INVESTIGATORS. 11 carried out for which preparations had been made during the previous winter. The report includes the gaseous exchange of the four authors and two others during grade walking in treadmill experiments in Berlin, and also on the railroad up the Rothorn, at Brienz, on Col d'Olen, and for a few experiments at the Gnifetti-Hiitte on Monte Rosa. Table 1 gives the computed percentages of efficiency for walk- ing on the different grades in these experiments. TABLE 1. Percentage of efficiency in grade-walking experiments made by Zuntz and Durig, arid their colleagues. Subject. Treadmill, Berfin, 12.7 p. ct. Brienz (500 meters), 25 p. ct. Rothorn (2, 100 meters), 25 p. ct. Col d'Olen (2,900 meters), 45 p. ct. Monte Ross (3,700 meters), 22 p. ct. (ca.). Zuntz and col- leagues : Waldenburg . . Kolmer . . . 32.4 U6.5 33.1 /38.6\ \ l 2Q.3f 43.3 42.6 29.8 42.7 33.8 31.8 32.7 38.0 32.1 41.9 32.1 29.5 32.5 33.6 27.0 17.7 19.8 Caspar! Muller 37.6 Loewy Zunta 1 22.6 Subject. Treadmill, Vienna, 21.6 p. ct. Neuwaldegg (summer), 16.4 p. ct. Neuwaldegg (winter) ,' 16.4 p. ct. Monte Rosa, 15.5 p. ct. Durig and col- leagues: Durig f34.9\ V34.1/ 31.1 30.3 31.7 30.1 24.0 20.9 15.2 21.8 21.2 18.5 21.5 19.8 Kolmer Rainer Reichel Durig, 2 in the report of his expedition to Monte Rosa, presents a critical view of the preceding studies and also gives the results obtained by himself and his companions, Kolmer, Rainer, and Reichel, at Vienna and on Monte Rosa. The computed percentages of efficiency for these experiments are also included in table 1. Like the preceding work of Durig, these studies were carried out by the Zuntz method, with all of the Durig refinements. Durig notes, in comparing the experiments with himself on the treadmill and while walking on the Neuwaldegg outside of Vienna, that the walking on the treadmill was apparently done with less expenditure of energy than walking in the open. He also finds that, within the speeds walked, the rate of walking had but slight effect on the metabolism per kilogrammeter. He was 1 Grade on treadmill: Kolmer, 18.2 p. ct.; Muller, 2d period, 26.2 p. ct. ; Durig, 2d period, 14.7 p. ct. ; Zuntz, on Monte Rosa, grade, 28.8 p. ct. 'Durig, Denkschr. d. math.-natur. Klasse d. kaiserl. Akad. d. Wissensch., 1909, 86, p. 294. 12 METABOLISM DURING WALKING. unable to detect any increasing effect of the grade, but the condition of the path had a marked effect in lessening the efficiency. Durig lays considerable emphasis in this report upon the question of the basal value to be used. He questions the correctness of the procedure of deducting a value for a horizontal component based upon results found in horizontal-walking experiments, which necessarily assumes that the expenditure of raising the body at each step in horizontal walking is the same as for grade walking, although he computed the energy cost for grade walking by this method. Undoubtedly, as Durig suggests, the greatest error in all the efforts to study the energy cost per kilogrammeter of grade-lift lies in assessing the value for the horizontal component. A comprehensive and thorough study of the energy expenditures of grade walking, per se, was carried out by Brezina and Kolmer 1 in Durig's laboratory with a motor-driven treadmill which could be adjusted to various grades and speeds. In addition to the level walking experiments, experiments were made with the subject walk- ing on grades of 4.7, 10.0 (ca.), 18 (ca.), 27.9, 35 (ca.), 39, and 42 per cent, while the total weights moved, including loads, were 70, 84, 93, 104, 114, and 124 kg. The speed of walking varied with the grade and the load, but the range was approximately 18 to 45 meters per minute. Naturally the lowest speeds were used on the higher grades. The method used in determining the basal metabolism was that of Zuntz, but the gas-meter was not carried on the back. The experi- ments were made with Brezina as the subject and in the forenoon, 1% hours after a breakfast consisting only of a cup of sweetened tea. In the calculation of the results, an average basal metabolism of 1,083 gram-calories per minute was deducted, this being derived from earlier experiments with Brezina. For the level walking they found an average value of 0.51 gram-calorie per horizontal kilogrammeter. The maximum amount of work done was at a grade of 27.9 per cent, when a weight of 104.5 kg. was moved at a speed of about 30 meters per minute. This produced 900 kg. m. of work, with an energy output above the basal of 10,000 gram-calories per minute. Brezina and Kolmer found a considerable variation in the respiratory quotients, but on the whole the increases obtained depended upon the amount of work done. In the experiments when the larger amounts of work were performed, the respiratory quotient was found to be as high as 0.98 and there were many experiments with a quotient over 0.95. The results of Brezina and Kolmer are further discussed by Brezina and Reichel, 2 who consider the data from a mathematical standpoint. These authors had previously shown 3 that the energy factor for the Brezina and Kolmer, Biochem. Zeitschr., 1914, 65, p. 16. 2 Brezina and Reichel, Biochem. Zeitschr., 1914, 65, p. 35. *Ibid., 63, p. 170. RESEARCHES BY OTHER INVESTIGATORS. 13 movement of 1 kg. 1 meter in horizontal walking within the range of the maximal economic velocity was not materially affected by loads up to 36 kg. and had derived a formula to express this generalization. Assuming that, according to their findings, the metabolism per hori- zontal kilogrammeter is independent of the speed and that the same relation exists for loads in grade walking as is found in level walk- ing (an assumption which they were not able to confirm), they derived a formula which they believe expresses in approximate form the energy metabolized per kilogrammeter of total weight and meter distance covered between grades of and 35 per cent. They find the optimum condition to be at a grade of 19.8 per cent, with a load of 19 kg., which required an expenditure of 10.1 calories for each kilogrammeter of grade-lift, or an efficiency of 23.1 per cent. It should be mentioned in this connection that Brezina and Reichel do not obtain net effi- ciencies, since they do not deduct the energy for the horizontal com- ponent, but compute the energy from the heat expended over the lying requirements. Brezina and Reichel find that for the limited speeds used the rate of walking was without influence upon the energy per kilogrammeter, and also that the total energy per kilogrammeter of grade-lift for grades between 10 and 40 per cent with superimposed loads of from 3 to 56 kg. varied from 10.1 (the optimum value) to 12.4 calories, while for lower grades of 2.5 to 7.5 per cent, the measure- ments were as high as 29.3 calories. This large difference was un- doubtedly due to the fact that the work at these low grades was too small a proportion of the total energy metabolized to be accurately determined. Brezina and Reichel give the data somewhat extensive mathematical treatment and derive certain formulae which, in their judgment, make it possible to calculate the increase in energy due to the load and the grade, provided certain limits of speed and load are not overlooked. They likewise include the efficiency as a constant function of the grade. The work of Brezina and his associates Kolmer and Reichel is by far the most extensive and painstaking of any of the studies on the physiology of walking, and their conclusions are suggestive. But, as they themselves say, though the study was carried out over a considerable range of speed and grade, the data represent the results of experiments with only one subject and considerably more data are required before their generalizations can be universally accepted. In physiological experimenting the use of but one subject has fre- quently been the basis of much adverse criticism of a piece of work. It is true that if but one isolated physiological factor is to be measured, this criticism is a serious one. In a study in which so complicated a process as the energy requirements of walking is concerned, the results of a careful series of experiments like those of Brezina and Kolmer, 14 METABOLISM DURING WALKING. even when but one man is used for a subject, may properly be employed for extensive generalizations, until deviations with other subjects are proved. While, therefore, we are in full accord with the criticisms of Cathcart, Lothian, and Greenwood, previously referred to, we still are disposed to consider a series of experiments, such as those made with Brezina, of most fundamental importance in the progress of our knowledge of the physiology of walking. Indeed, in our experiments the importance of contributing further observations on a number of individuals has played a not unimportant r61e in planning the research. Although Amar 1 reported a number of experiments in which the subject was engaged in horizontal walking, we have found hi his studies but two with grade walking. These were made with one subject walking on an 8 per cent grade and again on a 13 per cent grade, with and without a superimposed load of 7.3 kg. The experiments are but briefly reported and the data do not lend themselves to an extensive computation of the efficiency. In 1912, Douglas, Haldane, Henderson, and Schneider,* in an expedition to Pike's Peak, made an extensive series of horizontal- walking experiments which included two grade-walking observations, in which the gradient was 1 in 4, and the speed from 2 to 2.25 miles per hour. The special conditions of altitude, diet, and terrain make the results difficult of comparison with others. Waller 3 has made some estimates of the mechanical efficiency shown by men in ascending a staircase while breathing into a Douglas bag. The total volume of air exhaled and the carbon dioxide produced were determined in these experiments. By assuming a respiratory quotient of 0.85, Waller computed the energy expended during the work and believes that =*= 5 per cent was the range of error by this method. He reports data for 12 subjects varying in age from 18.5 to 63 years and in weight from 54.5 to 98 kg., who made the ascent of a 20-meter stair- case at an average efficiency of 33 per cent. Waller and de Decker 4 report an average mechanical efficiency of 32 per cent for T. R. P. in five ascents of the staircase. Later, in a comparison of bicycle with staircase ergometry, 5 17 experiments with A. D. W. showed efficiencies varying from 24.8 to 41.6 per cent for the staircase work. A complete report of this work of Waller has not yet appeared, but the results thus far published indicate very wide variations. Magne 6 has recently made a study of the changes in the energy 'Amar, Le moteur humain, Paris, 1914, p. 507. 2 Douglas, Haldane, Henderson, and Schneider, Phil. Trans. Roy. Soc. London, 1913, ser. B, 203, p. 185. "Waller, Journ. Physiol., Proc. Physiol. Soc., 1919, 52, p. Ixxii. 4 Waller and de Decker, Journ. Physiol., Proc. Physiol. Soc., 1919, 53, p. xxx. 6 Ibid., p. xliv. 'Magne, Journ. de physiol. et de path, gen., 1920, 18, p. 1154. RESEARCHES BY OTHER INVESTIGATORS. 15 expenditure in walking due to alterations in the number and length of the steps. By means of a rubber bag and a Tissot mask, the air expired during the experimental period was collected and samples analyzed. The subject was in the post-absorptive condition and walked with a carefully controlled frequency and length of step both on a level and on grades of approximately 5, 10, and 15 per cent. Magne found that the minimum net expenditure for a given distance on a level was obtained at an approximate speed of 63 meters per minute, and the average net efficiency for the grade experiments was not far from 20 per cent. GENERAL CONSIDERATIONS WITH REGARD TO PREVIOUS WORK ON GRADE WALKING. The technical difficulties necessary to be overcome in a study of grade walking are so great that only those who have had actual ex- perience hi such experiments are in a position to criticize fairly the work of others. The historical development of the method of studying metabolism during severe muscular work, not only that of walking but likewise of other forms, such as bicycle riding, has gradually led to a perfection of the technique. In reviewing the earlier work, it is noticeable that the criticism that applied to the horizontal-walking experiments applies with even greater force here, namely, that it became necessary in many series of experiments to work under some- what disadvantageous conditions. The dry gas-meter method, which has been used in so large a pro- portion of the earlier studies, has one great disadvantage in that no experiments can be made without a load. The carrying of a pack is to be expected in walking, and particularly in Alpine work, but the transportation of an apparatus such as a gas-meter and accessories, weighing many kilograms and attached to the back, even though in the most approved manner, still presents a problem in equilibrium that is attained only with considerable practice. While it is true that the transportation of loads is of great economic importance in indus- trial operations, and a knowledge of the efficiency in transporting loads is thus essential, yet thousands of people walk each day without a load in comparison with the individual with a load; consequently, observations which can be obtained on individuals not carrying loads are, we believe, of general interest. The modern method of substituting either a Douglas bag or a treadmill with a stationary meter is much to be preferred to the gas- meter method, provided essential differences between the work of walking in a well-ventilated room and that of walking in the free and open air on an equally even or satisfactory path are not subsequently developed. The Douglas-bag method is certainly a step in the right 16 METABOLISM DURING WALKING. direction, inasmuch as the load is almost imperceptible. Unfortu- nately, relatively few experiments have as yet been carried out with this method, and many of these have been hastily made and without the careful attention to technical detail given in experiments with other types of apparatus. Our own justification for making a study of the respiratory exchange in grade walking was, as stated earlier, the fact that it should serve in large part as a preliminary to a research upon grade walking in which direct calorimetry would be employed. The pronounced alterations in the respiratory quotient with severe labor, resulting in quotients at times appreciably over 1.00, make it a fair question as to whether or not the methods of indirect calorimetry give true indices of the actual heat-production under these conditions. Admittedly, the technical details to be overcome in making a study by direct calori- metry of the energy output of a man walking nearly to the limit of human endurance are very great, but it is believed that they may be overcome. In an effort to improve much of this technique, prior to inclosing the man in a hermetically sealed chamber, the treadmill experiments reported in the following pages were carried out at the Nutrition Laboratory. PLAN OF STUDY. The primary object of the experiments in this research was the determination of the energy expended by the human body in perform- ing the work of lifting itself to a definite elevation by walking up-grade. With a treadmill of unusual design and accuracy, a respiration appa- ratus capable of measuring an oxygen consumption of 3,000 c. c. per minute and over with great rapidity and exactness, much accessory apparatus for studying physiological factors, such as respiratory volume, respiration-rate, pulse-rate, step-lift, etc., it was believed that opportunity was afforded for a contribution to the general physiology of horizontal walking, also, which would amply justify the additional labor. As previously stated, it was at the outset considered that this whole research was preliminary to a subsequent study in which direct calorimetry would be employed. The total energy that is expended by the human body during grade walking is the sum of several factors, among which are (1) the energy required to maintain the vital functions, such as respiration and circulation, while the body is at rest, which may be termed basal energy; (2) the energy required for the muscular movements of the simple act of walking on a level; (3) the energy required to lift the body through a vertical distance corresponding to the elevation attained in the grade walking. Since the measurements of the metab- PLAN OF STUDY. 17 olism in the grade-walking experiments reported in this publication represented the total energy expended, it was necessary to know both the basal-energy cost and the cost of horizontal walking to obtain the energy cost of the work of elevation. Three groups of experiments were therefore carried out: (1) standing experiments, in which determinations were made of the energy ex- pended while the subject was standing quietly without support, these values being taken in the computations as the "rest" requirement; (2) horizontal-walking experiments with measurements of the energy output at different speeds of walking; from these the energy expended hi excess of the "rest" requirement was found, and thus the cost of moving 1 kg. of body-weight 1 meter on a level was determined; (3) grade-walking experiments from which the energy expended per kilo- grammeter of vertical lift in excess of the rest and horizontal-walking requirements was calculated for the different grades and speeds with the efficiencies for each condition. It was the intention to have the subject walk at certain definite rates in order that level and grade walking might be compared at the same speeds. Technical difficulties in the precise regulation of the speed of the treadmill made strict duplication too exacting a task in many instances and the results are consequently grouped according to the speeds which fell within limits of 5 meters per minute of each other. The grades were more easily maintained in the range between 2.5 to 45 per cent in rates of 5 per cent increase. It would have been desirable to have made both standing and horizontal-walking tests on each day that the grade- walking experiments were made; since, however, it was impossible to make experiments with a sufficient number of periods in each of the three groups, the only alternative was to secure an average value for both the standing and the horizontal-walking experiments. The data obtained during the horizontal-walking experiments, besides supplying the energy factor per horizontal kilogrammeter used in com- puting the energy to be deducted from the values for the grade-walking experiments, allow a comparison of this factor with that reported by other investigators, and we believe they present in themselves a sub- stantial addition to our knowledge of the physiology of walking. They also provide additional information as to the effect of the speed of walking upon the energy required per horizontal kilogrammeter, which has been reported to be practically independent of the speed for rates less than 80 meters per minute. Another element contributing to the work performed in either horizontal or grade walking in addition to the three factors previously mentioned is the elevation of the center of gravity of the body as it moves forward with each step. This elevation of the body represents a positive and appreciable amount of work. An effort has been made 18 METABOLISM DURING WALKING. to determine this elevation, or "step-lift," and to express it in terms of kilogrammeters of work. The proportion of increase in the energy due to this factor in horizontal walking may thus be obtained. If, in the grade experiments, the work due to the step-lift is added to the work of the vertical lift of the grade, the sum represents what may be called the total "work of ascent." In addition to these primary measurements, the experimental con- ditions were favorable for collecting data on other physiological factors, and some results are presented on the changes in the respira- tion-rate and pulse-rate, the pulmonary ventilation, and rectal body- temperature which accompany the changes hi the amount of work performed. A few observations on the changes in the blood-pressure between rest and exercise were made for comparison with the changes in the amount of work being done. The readiness with which the heart and lungs respond to the chang- ing demand of the body when work was either begun or ceased was also studied. The adaptability of the body to new demands at times, a demand approximating the limit of human endurance, necessitating an oxygen consumption of over 3,000 c. c. per minute is a factor in human economy that has been hitherto too little studied. The rapidity of adjustment after most strenuous exercise is of utmost importance in estimating "fitness" for the work performed. These experiments have been referred to as "transitional" experiments, and by measuring the oxygen consumption, ventilation, pulse-rate, and respiration-rate for successive fractions of a minute until either the normal or an approximately constant rate was obtained, the relation between the response of these physiological processes to the amount of work performed was obtained. METHODS OF MEASUREMENT. The group of apparatus used in this research was, in principle, that employed and described by Benedict and Murschhauser, 1 but with modifications essential for the increased amount of work to be per- formed. The principal apparatus employed were the universal res- piration apparatus for determining the gaseous metabolism and the treadmill for the measurement of the muscular work. In addition, accessory apparatus were used for securing data on the pulse-rate, pulmonary ventilation, body-temperature, etc., which were not obtained by Benedict and Murschhauser in their study. The general arrangement of the apparatus, with subject in position for an actual experiment, is shown in the frontispiece and, in part, in figure 1. Benedict and Murschhauser, Carnegie Inst. Wash. Pub. No. 231, 1915, p. 29. METHODS OF MEASUREMENT. 19 A n T- FIG. 1. Treadmill, with spirometer and various recording devices. The circulating air from the soda-lime containers of the respiration apparatus was conducted to the subject through the pipe A, and after passing through the pipes E and F and the spir- ometer G, was returned to the absorbers through the pipe H. Preliminary to the experi- ment, the subject respired into the room air through the 3-way valve D by the port d. At the beginning of the period, the valve D was turned and the subject was connected with the circulating-air system. By means of the by-pass B, the circulating air could be deflected through C and brought closer to the mouth of the subject, thus eliminating rebreathing. The parts of the apparatus specially indicated in the figure are: E, rubber hose to permit the adjustment of the mouthpiece to any height needed by the subject; G, spirometer with ventilation adder-wheel w and kymograph Z; g, pulley for reducing the movement of the pointer recording on the kymograph drum; 7, lever for operating valve D by the bar /, connected by cord with arm k; L, knob supporting the arm K; M, tension spring for operating valve D; N, NI, screws for adjusting the grade of the treadmill; O, spirit-level; P, motor, driving mechanism not shown; Q, Qi, adjustable brake on the motor shaft; R, counter for recording revolutions of front pulley; S, long wooden fork fastened to the shoulders of the subject by elastic webbing; the rise and fall of this fork is transmitted by T to the step-lift counter and kymograph, not shown in the drawing; U, U\, electrodes for securing electro- cardiograms of the pulse-rate; V, electrode for grounding the subject; W, W\, brass-gauze brush and leads for grounding the treadmill; this brush was discarded when the method was changed to that of grounding the subject by the electrode V; X, step-counter with spring attached to the subject's ankle; Y, framework protecting the spirometer. 20 METABOLISM DURING WALKING. UNIVERSAL RESPIRATION APPARATUS. The universal respiration apparatus in its various adaptations has been frequently described in the publications from this Laboratory. 1 Briefly stated, it consists of a closed ventilating air-circuit, with pro- visions for a moderate deigrete of expansion in the air-volume and con- nection with the subject by means of a mouthpiece or nosepiece. The air is kept in motion by a rotating ventilator or blower, actuated by an electric motor, which forces the expired air through absorbents for moisture and carbon dioxide arid, returns it to the subject for rebrejath- ing aftetr the air has been moistened and the oxygen dejficit has been made up from an oxygen-supply connected with the system and metored. Sulphuric acid is used for the water-absorbent and moist soda-lime for the carbon-dioxide absorbent. The combined increase in the weight of the soda-lime containers and the supplementary watdr- absorbe^ 1 gives data fojr calculating the volume of carbon dioxide expired by the subject. The amount of oxygen consumed is deter- mined from the readings of a calibrated integrating meter connected with the oxygen-supply. The absorbing system, mounted on a two- shelved table, is in duplicate, with suitable valve connections which permit the use of either series of absorbers at will. Since the amount of work to be performed was greater than in the study made by Benedict and Murschhauser, the ventilating system was equipped with a larger motor and driving-pulley. The speed of the one-sixth horse-power electric motor employed was controlled by a rheostat, fixed upon the front of the table, which permitted the varia- tion of the ventilating air-current between 65 and 100 liters per minute. The two sulphuric-acid containers, or "Williams bottles," which were inserted in the system next to the blower, each had a capacity of 2.5 liters and were followed by a train of two large soda-lime containers for the absorption of the carbon dioxide, and a third large Williams bottle or air-drier for absorbing any moisture carried over from the moist soda-lime. Moistener. The dry air, after it left the carbon-dioxide absorbers, was moistened by passing it through water contained in a large Williams bottle. None of the subjects complained that the ah* was too dry. A test was made of the percentage of humidity by inserting a psychro- meter in the air-circuit, and an average figure of 70 per cent was found when the rate of ventilation was highest. This figure has been used hi reducing the volume of the pulmonary ventilation to standard conditions. Spirometer. In the research of Benedict and Murschhauser, a rubber bathing-cap was used as a tension equalizer for fluctuations Benedict, Deutsch. Archiv f. klin. Med., 1912, 107, p. 156; Benedict and Cathcart, Carnegie Inst. Wash. Pub. No. 187, 1913, p. 27; Benedict and Murschhauser, Carnegie Inst. Wash. Pub. No. 231, 1915, p. 31; Carpenter, Carnegie Inst. Wash. Pub. No. 216, 1915, p. 21. METHODS OF MEASUREMENT. 21 in the volume of air in the closed circuit. 1 In the present research, a large spirometer (G in figure 1) was employed, 8 liters in capacity, which was built on the principles already described in reports from this Laboratory. 2 This spirometer was placed on a small table at the left of the treadmill and close to the subject. A light, non- viscous oil was used in the spirometer rather than water. None of the subjects com- plained of odor from the oil; in fact, none of them knew that oil was used. During the experiments, when severe muscular work was being performed, the respirations of the subject became so deep that the movements of the spirometer-bell were too large to be recorded on the usual kymograph-drum. To reduce the movement of the pointer, the thread supporting the bell was passed through a pulley to which the counterpoise and the pointer were attached. (See g, fig. 1.) The movement of the pointer was thus reduced one-half, but this had its disadvantage in that it doubled any error in the reading, since all readings must be multiplied by 2. As in the walking experiments, the oxygen consumption was frequently 8 to 10 times the resting value, this doubling of the error played no role save in the "rest" experiments. In measuring the rate of oxygen consumption in certain tests in this research, no oxygen was admitted for a portion of the experimental period and the lower capacity limit of the spirometer was thus reached in a few minutes. For these few tests, use was made of the double spirometer shown in figure 2. A duplicate spirometer A is attached to the principal one B by a large tube E and a 3-way valve D. The oxygen is introduced by means of the connection (7. Both spirometers were filled with pure oxygen before an experiment, and the usual readings taken on the main spirometer B. As soon as the subject was connected with the ventilating system, the bell of the spirometer B fell rapidly with each respiration as the oxygen was consumed. When the oxygen was at as low a level as seemed wise, the three-way valve D was opened and oxygen from the duplicate spirometer A was forced into B by pushing down the bell of A. The valve was then closed and A was again filled from the oxygen cylinder through the connec- tion C. This was repeated as often as necessary. The kymograph curve thus shows a succession of hills and valleys (see fig. 15, p. 183), due to the fact that the pointer rose on the scale of B as the oxygen was consumed and then sank when the supply from the reservoir A was forced into the main spirometer B. The time of filling spirometer B was scarcely 2 seconds, and not over one or two respiration tracings were lost in the process. Benedict, Am. Journ. Physiol., 1909, 24, p. 345. See, also, Carpenter, Carnegie Inst. Wash. Pub. No. 216, 1915, p. 24. 2 Benedict, Deutsch. Archiv f. klin. Med., 1912, 107, p. 172; Carpenter, Carnegie Inst. Wash. Pub. No. 216, 1915, p. 37. 22 METABOLISM DURING WALKING. Pressure conditions. The large volume of air being forced through the air-puri- fying system by .the rapidly moving blower created considerable pressure in the system, and a small mercury mano- meter was introduced at the head of the absorber table immediately in front of the soda-lime bottles to act as a safety- valve in case of need. The pressure indi- cated by this manometer when the blower was delivering air at the rate of 100 liters per minute was from 130 to 180 mm. of mercury, depending upon the condition of the soda-lime and the amount of acid in the Williams bottles. From the absorber table to the valve of the mouthpiece, a f-inch galvanized-iron pipe was used and all joints, where practical, were soldered to reduce possibilities of leaks when there was a high pressure on the system. On the return line from the valve to the spiro- meter (see F, fig. 1) the pipe was 6 cm. in diameter, ordinary galvanized-iron con- ductor-pipe being used for the most part. This reduced the pressure so that just beyond the mouthpiece water manome- ters showed a variation in pressure of but 2 to 10 mm. of water, and the opening of a petcock under the spirometer had scarcely any effect on the position of the bell, so evenly balanced was the pressure. Adjustment to subject. To permit raising and lowering the con- nections with the subject on the treadmill, a 2-foot length of corru- gated flexible metal tubing was introduced on one side and on the opposite side a rubber hose was inserted (E, fig. 1), 5 cm. in diameter, of about the same length as the metal tubing. This permitted the nec- essary up-and-down adjustment to the height of the subject and the pitch of the treadmill. For conducting the air from the spirometer to the absorber table, rubber tubing 28 mm. in diameter was used. Meter. An integrating meter, 1 capable of being read to 10 c. c., was used for measuring the oxygen consumption. As the experimental periods seldom exceeded 12 minutes and the room temperature was fairly uniform, temperature changes were for the most part insignifi- cant, though always measured. The meter was equipped with an J The meter used was made by the American Meter Company, New York, N. Y., their 0.1 cu. ft. wet test meter (No. 613), fitted with dial to read in liters. One revolution is equivalent to 3 liters, the total reading will run to 1,000 liters, and the volumes may be read to 10 c. c. FIQ. 2. Double epirometer. B, main spirometer; A, duplicate spirometer used as reservoir; C, connection with oxygen-supply ; D, three-way valve between A and B; E, rubber tubing connecting A and-B. METHODS OF MEASUREMENT. 23 accurate thermometer, which was read at the beginning and end of each experiment. The average of these readings was used for the slight correction of the volume of oxygen due to temperature changes of the meter. The meter was calibrated 1 by passing weighed amounts of oxygen through it at various rates, and the factors thus obtained were used in all subsequent computations. Several calibrations were made during the course of the investigation with approximately uni- form results, which were but the fraction of 1 per cent high. This meter proved very satisfactory, especially the integrating feature, which eliminated the danger, ever-present with other types of meters, of failure to record accurately the total number of revolutions of the pointer. The oxygen used in the experiments was made and supplied by the Linde Air Products Company. Barometer. In the 12-minute periods of this research the barometric changes under ordinary atmospheric conditions were almost negligible. For measuring such changes a barograph was used, checked by a re- liable barometer, and read to 0.1 mm. These readings were made at the beginning and end of each period, the average being used for reducing the data for the oxygen consumption to standard conditions. Kymograph. The usual Porter kymograph 2 was employed, but in place of records on smoked paper, pen-and-ink tracings on an unsmoked glazed paper were obtained. The pen, which was fastened to the counterpoise of the spirometer-bell, was a small glass capillary pen with platinum tip, such as is employed on many forms of automatic reading devices in large steam and electric plants. 3 This method was found to be simpler and cleaner than working with smoked paper and a varnishing solution. The speed of the kymograph-drum was 1 revolution in 15 minutes. A small pen, such as is used with the ordinary barograph, was attached to a signal magnet connected with the clock, and a record thus obtained in minutes on the glazed paper. Respiration counter. The number of respirations during the period was at first counted from the tracings of the pen attached to the spiro- meter-beM. Later a device (see fig. 3) was attached to the arm of the spirometer (see A, fig. 3). The cord B, leading to the counterpoise of the spirometer-bell, by rubbing on the fiber sleeve C caused the platinum points E and E\ to dip into the mercury cups D and D\ and complete a circuit to a counting device known in the telephone trade as a "p. b. x. message register." (See fig. 4.) This device proved a great labor-saver in counting the respiration tracings on the kymo- graph. Benedict, Phys. Review, 1906, 22, p. 294. ^Harvard Apparatus Company, Dover, Massachusetts. The pen which gave the most satisfactory results was the Cochrane pen, supplied by the Harrison Safety Boiler Company of Philadelphia, Pennsylvania. It was about 40 mm. long and 6 mm. in diameter. With ordinary care the pen withstood a remarkable amount of use before it was worn out. 24 METABOLISM DURING WALKING. B FIG. 3. Respiration counter. A, spirometer frame; B, cord from spirom- eter-bell leading to counterpoise; C, fiber sleeve; D, D\, mercury cups; E, Ei, platinum-pointed fork for com- pleting the circuit through D and Di\ F, stop; G, leads to electrically operated counter shown in fig. 4. Ventilation recorder. The total volume of air drawn into the lungs was registered by means of an attachment previously described, 1 and commonly referred to as the "ventilation adder." This consists of an aluminum wheel (w, fig. 1) attached to the apparatus in such a manner that each down- ward movement of the spirom- eter-bell due to inhalation by the subject moves the wheel upward. By means of a signal magnet, each revolution of the wheel is recorded upon the kymograph. From this graphic record and the volume corresponding to a revolution of the wheel, the total inspira- tory Ventilation Can be CalcU- FlG - 4. Electrical counter for recording number of i A. j A c. L j.i_ i respirations. For operating device and con- lated. At first the pulmonary nections with the apparatus, see fig. 3. ventilation during grade walk- ing was found by actual measurement of the pen tracings on the kymo- graph, but later with the ventilation adder. The ventilation data secured have been reduced to standard conditions for temperature and pressure for recording in the tables. Mouthpiece. The mouthpiece used was of the Denayrouse type. 2 At the beginning of the study strips of surgeon's plaster across the lips ^Benedict, Deutsch. Archiv f. klin. Med., 1912, 107, p. 176; see also Carpenter, Carnegie Inst. Wash. Pub. No. 216, 1915, p. 40. 2 P. Regnard, Recherches experimentales sur les variations pathologiques des combustions respiratorires, Paris, 1879, p. 286; also Carpenter, Carnegie Inst. Wash. Pub. No. 216, 1915, p. 54. METHODS OF MEASUREMENT. 25 were used with all the subjects to prevent possible leakage around the mouthpiece, but later these were omitted with W. K. and E. D. B. after they had become accustomed to the conditions. The normality of long-continued breathing through the mouthpiece, especially under the conditions of the grade-walking experiments, was tested in a series of experiments. The results of these tests are discussed on page 177. The valve-operating device. The method of operating the valve which connects the subject with the air-circuit is shown in figure 5, page 28. An arm on the stem of the valve is connected by a cord F to a bar K, which is supported on a button L. (See, also, fig. 1, p. 19.) When the operator pushes forward the lever J, L is forced from under the bar K and the tension of the spring M turns the valve. Resetting the button L and shifting the cord to the other side of the arm k (see fig. 1) permit the closing of the valve at the end of the period by the same method. This arrangement allows the operator to stand behind the subject, who thus has no knowledge as to when the period is to begin and end. The proper operation of the apparatus requires that the valve should be opened and closed at the end of a normal respiration, which is noted by the movement of a bit of goose-down affixed to the outlet of the valve. This material was not affectecl by the moisture of the breath, and, being light, instantly showed the point of change in the current of air at the end of an expiration. By-pass. As in other experiments made in this Laboratory on muscu- lar work, 1 the ventilating air-current was carried to within a few cen- timeters of the mouthpiece by means of a supplementary pipe C (fig. 1), operated by a by-pass valve B. This by-pass valve was opened by a hand lever a few seconds after the beginning of an experimental period and closed a few seconds before the end of the period. This prevented any possible difficulty hi obtaining sufficient ventilation for the subject and obviated an excessive dead space. Rate of ventilation. The rate of ventilation during all of the walking experiments was the maximum capacity of the blower, namely, 100 liters per minute, while for the standing experiments a rate of 65 liters per minute was generally maintained. TESTS OF THE UNIVERSAL RESPIRATION APPARATUS. Although the efficiency of the absorbing system of the universa respiration apparatus has been thoroughly and repeatedly demon- strated, it seemed advisable to test this point further before beginning the research, since in the walking experiments a ventilating air-current with a rate as high as 100 liters per minute was to be used in place of the current of 30 to 40 liters per minute employed in most of the researches with this apparatus. If the water-absorbers were inefficient, moisture would be carried over to the carbon-dioxide absorbers and Benedict and Murschhauser, Carnegie Inst. Wash. Pub. No. 231, 1915, p. 33. 26 METABOLISM DURING WALKING. there collected; under these circumstances the change in weight of these absorbers would not represent the amount of carbon dioxide expired by the subject, but would give higher values. If, on the other hand, the air-drier in the soda-lime train (i. e., the Williams bottle following the two carbon-dioxide absorbers) were inefficient, so that moisture carried over from the moist soda-lime was not wholly absorbed by the sulphuric acid in the Williams bottle, the total increase in weight would be less than the actual amount of carbon dioxide expired by the subject. Efficiency of the water-absorbers. During rest experiments the usual rate at which the absorbing system is run is not far from 30 to 35 liters per minute. For testing the efficiency of the water-absorbers for the special demands of this research, the absorbing system was run at 65 to 100 liters per minute without a subject. The gain in weight of the water-absorbers and the loss in weight of the moistener were then com- pared. If the water-absorbers were efficient, their gam in weight would be equal to the loss in weight of the moistener. One such test showed a difference after 1 hour of 0.19 gram. If, in 12 minutes (the usual length of a period), such an amount of unabsorbed water were carried to the soda-lime containers and there absorbed, the error in the deter- mination of the carbon dioxide expired would amount to 1.5 c. c. per minute. In another series of experiments with five periods, the first Williams bottle gamed 116 grams, while the second gained only 2 grams. In still another test an additional Williams bottle was used. The first gained in weight 165.55 grams, the second 4.70 grams, while the third lost 0.1 gram in a period of 3 hours'. As it was the practice to remove the first Williams bottle each day and advance the second Williams bottle to first place, while a freshly filled bottle was used for the second water-absorber, it may be safely assumed that none of the moisture in the ventilating air-current reached the carbon-dioxide absorbers. In the usual rest experiments, in which the ventilation is about 30 liters per minute, the "error" would be negligible in all cases. Efficiency of the air-drier. The second point, viz, that the carbon- dioxide absorbers lost no moisture that was not recovered by the air- drier, was tested by passing the ventilating air-current through the soda-lime containers, which were weighed separately. The moisture taken up by the air in passing through the moist soda-lime should then be entirely removed hi the following Williams bottle or air-drier. The largest gain found during any test was equivalent to an error of 3 c. c. per minute in the carbon-dioxide determination, while the average error in a series of tests was but a fraction of 1 c. c. per minute. It was considered, therefore, that the absorbers as used in this research were efficient, even at the high rate of ventilation of 100 liters per minute. During the standing experiments the rate of ventilation was 65 liters per minute, which allowed still greater efficiency hi the absorbers. METHODS OF MEASUREMENT. 27 Tests for tightness. The care used in making all of the various joints in the system air-tight was well worth the effort, for the apparatus was surprisingly free from leaks. At the beginning of each day's experi- menting a preliminary test for tightness was always made, and if the pointer on the kymograph-drum showed any variations within 3 min- utes, a leak was sought for. During the research further tests of 15 and 20 minutes were likewise made for possible leaks. Early in the experiment these longer tests were made daily, but later they were made but once a week or even once in two weeks. Tests of air in the system. Before beginning the experiment of the day it was the practice to empty the bell of the spirometer and intro- duce 4 or 5 liters of oxygen into the system. The ventilating appa- ratus was then operated for a few minutes, the spirometer again emptied, and refilled with oxygen. This prevented any danger of deficiency in the oxygen-content of the air and an accumulation of nitrogen. Duplicate analyses of the air after the completion of a series of seven successive experimental periods with W. K. on one day gave results for oxygen of 21.90 and 21.93 per cent. TREADMILL. A detailed description of the treadmill was given hi the report of the previous study in which this apparatus was used. 1 It consists of an endless leather belt which travels over two broad wooden pulleys, sup- ported on ball bearings, at the ends of a wooden frame. The mill is actuated by a ^2 h. p. electric motor. The belt between the pulleys is supported by a considerable number of steel tubes, set close together but without touching in a steel framework. Each tube is fitted at its two ends with annular steel ball bearings. A rolling, frictionless sur- face is thus provided for the man to walk upon, which is both sub- stantial and smooth. The speed of the motor may be varied at will. Some slight alterations were made in the treadmill for this research, but it was essentially as used in the previous study with the subject walking. The general arrangement of the apparatus is shown in the frontispiece and in figure 1, page 19. Distance counters. The use of the two counters recording the num- ber of revolutions of the front pulley of the treadmill was continued in this research, except that the "continuous counter," for recording the total number of revolutions, was moved to the rear of the treadmill frame and operated by a wire from the front pulley. This change was made so that the counter might be in view of the operator standing at the absorber table. The other counter, which is shown in figure 5, and records the number of revolutions of the pulley during the experi- mental period, is known as the "period counter." It is fastened to the front pulley of the treadmill and is operated. by the bar /, which 'Benedict and Murschhauser, Carnegie Inst. Wash. Pub. No. 231, 1915, p. 34. 28 METABOLISM DURING WALKING. turns the valve connecting the subject with the ventilating circuit. When J is thrown at the beginning of the period, it forces the arm A from its position at stop B over to stop C. This changes the position of the bar D from d to d\. In the latter position the button E strikes against D with each revolution of the pulley, this contact operating the counter R. A measurement of the outside circumference of the belt (4.355 meters) and a series of tests showed that one revolution of the pulley was equivalent to 1.328 meters. Hence, from the total number of revolutions of the pulley as recorded by the counter during the period and the equivalent of one revolution of the pulley (1.33 meters), the exact distance walked by the subject during the period could be calculated. By readings of the "continuous counter" at the times when the valve is opened and closed, itfis possible to verify the records of the "period counter," so that a check on the record of the distance walked was obtained. FIG. 5. Detail of valve-operating device and period counter. Valve-operating device. J, bar which, when pushed forward, forces button L from under bar K. The tension of spring M then acts through cord F, operating arm k and valve D in figure 1 (p. 19), connecting subject with the ventilating circuit. (See /, \k, D, J, L, K, and M, fig. 1, p. 19.) Period counter. When the bar A is against the stop B, the pivoted brass bar D is in position d. The brass button E then slides past the bar D without displacing it. When the valve- operating device J is thrown forward, the bar A is pushed against the stop C and the bar D comes into the position dj. The button E then strikes the bar D on each revolution of the pulley and the displacement of D operates the counter R, giving a record of the number of revolutions of the front pulley during the experimental period. (See also fig. 1, p. 19.) Control of the speed of walking. By means of a stop-watch the time necessary for 10 revolutions of the front pulley as shown by the coun- ter was determined, and then, by reference to a previously prepared table, the speed of the treadmill could be readily obtained. The speed was controlled largely by means of the starting-box, which permitted moderate adjustment. As the experiments progressed, however, there METHODS OF MEASUREMENT. 29 was frequently a change in the speed of the treadmill. This change was gradual and could not be easily detected. It often happened, therefore, that when the speed was properly adjusted at the beginning of the experiment it would be found that as tune passed the rates of walking for the different periods varied slightly from each other. During the walking experiments in which high grades were employed, use was made of the brake Q, Qi, bearing on a pulley fixed to the motor shaft, to aid in securing satisfactory speed adjustments. (See fig. 1.) Angle of ascent. By means of two nuts sunk in the head of the tread- mill frame and two long screws (see N, and NI, fig. 1, p. 19), it is possible to elevate the front end of the treadmill to an angle of slightly over 45. A spirit-level (0 in fig. 1), fastened to the front of the tread- mill, indicates when both sides have been adjusted equally, so that the belt will run smoothly and true. To determine the elevation of the treadmill, a light wooden triangular frame was constructed, which is shown in figure 6. This was pivoted at A and E and could be adjus ted at B, by means of a slot and set-nut. The distance between A and C was exactly 100 cm. When used to find the angle of elevation, this frame was placed upon the walking surface of the treadmill, with the edge AE resting on the leather belt. It was then adjusted at B until FIG. 6. Framework used in determining the angle of ascent. the surface AB was perfectly level, as shown by the spirit-level S. The elevation DC was next measured and used to find the sine of the angle, or the "slant-height." Since AC is 100 cm., the slant-height may be readily expressed as per cent. Accordingly, when the grade is given as 10 per cent, it is meant that the subject in walking a linear distance of 100 meters raised himself to a height equivalent to 10 meters. It should be borne in mind that for the 100 linear meters thus walked, the energy expended over and above the standing requirements was made up of the energy required (1) for the elevation of the body and (2) for transporting the body over the horizontal component. This horizontal component was found from the cosine of the angle. Thus, the subject, in walking on a 10 per cent grade at a rate of 100 meters per minute, walked a linear distance of 100 meters and the vertical component would be 10 meters, while the horizontal component would be 100 X cosine 5 44' 30", or 99.5 meters. 30 METABOLISM DURING WALKING. MEASUREMENT OF THE STEP-LIFT. With each step in walking, the body is raised to a greater or less degree in a vertical direction, and this becomes an appreciable factor in the amount of work which is done. In the previous research in this Laboratory on the muscular work of walking, a dual record of these movements was obtained by means of a work-adder wheel, the spring pointer introduced by Professor Carl Tigerstedt, 1 and a kymograph record. The same method of measurement was used in this research (see fig. 7), except that the cord leading to the work-adder wheel was not attached directly to the subject. Instead, a light wooden fork was employed, which was 2 meters long and pivoted at one end, while the prongs were held closely at the subject's shoulders by elastic webbing^ Fio. 7. Step-lift recorder. T, cord fastened to fork at back of subject (see fig. 1, p. 19); A, spring providing tension on cord T; B, recording wheel revolved by the friction of cord T; C, laminated spring-steel pawl to prevent back-lash ; D, pen for tracing record ; E, signal magnet and pointer for recording time. (See S, fig. 1, p. 19.) The cord T (figs. 1 and 7) from the work-adder wheel was fastened to this fork at a point directly behind the subject's neck. Although this attachment was not so near the center of gravity of the body as it might be, the results obtained with it were very positive and showed such slight movements as shifting the weight of the body from one foot to the other a movement scarcely noticeable to the observer while it was less affected by the relative position of the subject on the treadmill. The work-adder wheel was directly con- *C. Tigerstedt, Skand. Archiv f. Physiol., 1913, 30, p. 299. See special application of this pointer under the conditions of this research in Benedict and Murschhauser, Carnegie Inst. Wash. Pub. No. 231, 1915, p. 39. METHODS OF MEASUREMENT. 31 nected to the shaft of a revolution-counter, and a record of the total movement of the wheel was thus obtained. The total distance the body was raised would theoretically be that found by multiplying the number of revolutions of the wheel by its circumference. These read- ings were made for 10 minutes during every period 12 or 13 minutes in length. Another change in the procedure was the use of ink in place of smoked-paper tracings on the kymograph drum. The speed of the kymograph was regulated to one complete revolution in 3 minutes. If a lower speed than this was used, the tracings of the pen were frequently superimposed upon one another, making it difficult to distinguish the individual steps. As it was necessary to readjust the kymograph between the end of each revolution and the beginning of the next one, only three 3-minute tracings could be obtained during the period. The average of these three 3-minute records was taken as the average elevation of the body per minute during the entire period of 12 or 13 minutes. The tracings upon the kymograph-drum were used, how- ever, simply to check the records of the step-lift counter in case it failed to act properly. A criticism 1 has recently appeared of the method used by Benedict and Murschhauser 2 in measuring the step-lift, to the effect that, in walking, their subject changed his position on the treadmill, thus changing the length of the cord from his back to the pulley from which the cord ran to the kymograph. Since the criticism would apply to some extent to the method used in this research for measuring the step- lift, several experiments to test this point were made on a subject not used in the research of Benedict and Murschhauser, as neither of these was available. A small incandescent lamp was inclosed in a tin can with a hole in it through which the light would shine. One of these lamps was fastened to the back of a subject at the point of attachment used by Benedict and Murschhauser (the waist-line) and a second light to the point between the shoulders used in the present research. For a scale of measurement, two lights, 1 meter apart, were affixed to a board centered in the same plane and behind the subject. Photographs were then taken of the movements of the spots of light at the waist and shoulders, respectively, during the cycle of one double step when the subject was walking on a level and on grades of approximately 10 and 25 per cent, with a speed in each case of 71 to 74 meters per minute. These photo- graphic records were made not only with the camera stationary, but also with the camera rotated, so that tracings were obtained across the full length of the photographic plate. By measuring the spacing of the light spots on the photographic 'Liljestrand and Stenstrom, Skand. Arch. f. Physiol., 1920, 39, p. 167. 'Benedict and Murschhauser, Carnegie Inst. Wash. Pub. No. 231, 1915, p. 39. 32 METABOLISM DURING WALKING. plate, and the distance on the 1-meter scale, it was found that in walk- ing on a level there was an average total forward-and-back movement at the waist of 1.98 cm., and at the shoulder of 0.79 cm., corresponding to a displacement from the vertical of 0.99 and 0.40 cm., respectively, while for the 10 and 25 per cent grades the displacement was even less. For a radius of 1.5 meters, which represents the length of the cord from the shoulders to the pulley, and which connects the subject with the step-lift counter, this displacement would amount to a rise above the horizontal of 0.01 cm., an amount too small to be considered. A comparison was also made at this time between the respective readings of the perpendicular lift, as shown by the light spot at the waist (Benedict and Murschhauser method), and that at the shoulder (H. M. S. method), and of the kymograph tracings taken simul- taneously. On one series of plates it was found that, for horizontal walking, the movement of the light spot at the waist was larger than that at the shoulder by 1 per cent, while the movement of the shoulder light spot was greater than that recorded by the kymograph by 1.5 per cent. On another series of plates it was found that the shoulder movement was slightly larger than the waist movement. In either case it may be assumed that the variations agree within 1 or 2 per cent of each other. In the case of the grade walking the differences were of the same order. Measurements were likewise made with the subject walking up the inclined treadmill when it was stationary and again when it was running. The subject with the light at the waist stepped from a stool on to the treadmill and walked to the top, tjhus giving an opportunity for the measurement of the step-lift superimposed on the grade-lift. The mill was at an incline of 18.4 per cent. By measuring the light spots recorded on the plate when the subject walked up the stationary mill, it was computed that the grade was 14.7 per cent, i. e., the light spots did not correctly show the grade by 3.7 per cent. From the plates made when the subject walked up the mill while it was running, the grade, computed from the light spots, was 19.9 per cent, or 1.5 per cent too high. Evidently the measurements of the step-lift can only be regarded as approximate. The average step-lift, measured under these conditions, was 5.23 and 6.48 cm. per step, respectively, with the mill stationary and running. Assuming 110 steps a minute, there was a lift of approximately 7 meters per minute when the mill was running. From table 55 (see p. 214), we find that E. D. B. on December 15, walking on a 15 percent gradeand with a speed of 75 meters per minute, had an average step-lift of 4.89 meters per minute, as measured by the kymograph; and on January 1, with a 20 per cent grade and a speed of 80 meters per minute, it was 5.57 meters per minute. If these figures are increased by 1.5 per cent to correspond with the measurements from the photographic METHODS OF MEASUREMENT. 33 records, which were that much higher than the kymograph records (p. 32), his step-lift per minute would have been 5.0 and 5.7 meters as compared with 7 meters per minute for the subject of this test. Considering the difference in the grades and speeds, as well as the difference in subjects, and the considerable lapse of time between the results obtained in the research and in these later tests, there is more approximation here than might have been expected. Step-lift technique during grade walking. The use of the fork on the shoulders, as indicated in figure 1, during experiments on horizontal walking, is, we believe, without serious criticism. After our series of experiments had been completed, the results computed and tabulated, and an analysis of the data was being made, a criticism arose to the effect that the device pictured in figure 1 would not record the true step- lift, but might include in its registration a not inconsiderable part of the grade-lift. It appeared that the most logical procedure would be to place the fork parallel with the belt of the mill and to run the cord from the fork to the first pulley in a line at right angles to the belt of the mill, continue it over the second pulley, and then down to the pointer. It was argued that by this method no movement in the direction that the belt was traveling could be registered, except that of a very long pendu- lum, which, at this arc, namely, 110 cm. or more, would be negligible. Consequently, during the preparation of this manuscript for publica- tion, a series of experiments was made to test the effect of this change n procedure. Since the results relate more particularly to the study of the step-lift during grade walking, their discussion is deferred until the results of the grade-walking experiments are considered. (See p. 243.) METHOD OF STEP-COUNTING. For securing a record of the number of steps taken by the subject, a counter attached to the rear end of the treadmill was connected with the ankle of the subject by means of a long, weak, spiral spring. (See -X", fig. 1.) This spring had sufficient tension to operate the counter when the leg was thrown forward, but at the same time put no restriction upon the movements of the subject as he walked. As it was not possible to obtain the reading at the exact beginning of the period, it was the practice to read the step-counter at the end of the first minute of the period and again at the end of the eleventh. The difference in the records, when multiplied by 2, gave the total number of steps taken during the 10 minutes of a period 12 or 13 minutes in length. APPARATUS FOR DETERMINING THE PULSE-RATE. Benedict and Murschhauser, 1 in their report on the energy trans- formations in horizontal walking, recorded a few pulse-rates with the 'Benedict and Murschhauser, Carnegie Inst. Wash. Pub. No. 231, 1915, pp. 54 and 55. 34 METABOLISM DURING WALKING. subject walking which were taken by the writer with a string galvano- meter. These were made largely to test the possibilities of this method for determining the pulse-rate during muscular work. While condi- tions did not permit at that time the collection of any considerable amount of data, the method was shown to be practicable. The results here reported were first obtained by means of a Bock-Thoma oscillo- graph and later by the use of a Cambridge string galvanometer, somewhat modified, especially as to the registering apparatus. OSCILLOGRAPH. The Bock-Thoma oscillograph 1 was equipped with four filaments, but only one was used. This was of platinum with a diameter of 0.0025 mm. and a resistance of 5,000 ohms. In place of the regular time equipment, a Jaquet graphic chronometer was employed, the pointer of which interrupted a beam of light in front of the camera- slit. As only the pulse-rate was desired in these experiments, the speed with which the photographic paper was supplied to the camera was reduced to approximately 25 cm. per minute. At this speed each pulse-beat could be easily counted on the record and the distance between the second marks could be readily estimated to tenths. It was found difficult at that time to obtain photographic paper of American manufacture that was sufficiently sensitive for use with this instrument, while the paper originally supplied with the instrument was expensive and did not keep well. Ultimately a satisfactory European paper was obtained. The greatest difficulty, however, was found with the filaments of the oscillograph. These were exceed- ingly delicate and liable to damage. Finally, when war conditions made it impossible to replace broken filaments, the use of the oscillo- graph was discontinued. A typical record of the pulse-rate as ob- tained with this instrument is given in C, figure 8. CAMBRIDGE STRING GALVANOMETER. In the fall of 1916 a Cambridge string galvanometer, which had previously been used in the psychological work of the Laboratory, was employed for measuring the pulse-rate of the subjects in the walk- ing experiments. For this purpose a camera of the so-called Morse type 2 was substituted for the camera provided with the Cambridge instrument. This apparatus was so changed that the mechanism supplying the photographic paper to the camera was driven by a 1/80 h. p. motor of 2,200 r. p. m., equipped with a rubber friction drive in place of the usual worm and gear, also with a suitable set of reducing pulleys. The speed with which the paper was being fed to the camera was indicated by a pointer fixed to the feed-shaft revolving over a graduated dial. By means of a hand rheostat, the speed of the ^roedel, Theo. and Franz, Deutsch. Archiv f. klin. Med., 1912, 109, p. 52. 'Manufactured by Edelmann and Sohn, Munich, Germany. FIG. 8. Typical records of pulse-rate as obtained with oscillograph and string galvanometer. A and B, records with string galvanometer: C, record with oscillograph. T, time; P, pulse-rate. METHODS OF MEASUREMENT. 35 paper could be varied from 25 to 100 cm. per minute. As with the oscillograph, the rate of speed in supplying the paper to the camera was kept as low as was consistent with clear registration, and the time was recorded by means of a Jaquet chronometer. Typical records of the pulse-rate as obtained with the Cambridge string galvanometer, with the modifications noted, are given in A and B in figure 8. ELECTRODES. In the beginning of the research the subject was connected with the galvanometer by means of zinc rods, wrapped in flannel and moistened with zinc-chloride solution. These he carried in his hands. The difference in pressure with which the subject at times gripped the elec- trodes caused a varying resistance in the system and led to more or less difficulty. Various other forms of electrodes were tried, but those which were most satisfactory and which were used in practically the whole study consisted of brass disks about 2 cm. in diameter, embedded in kaolin mixed to a paste with dilute zinc-sulphate solution. This paste was plastered on the chest just above and below the nipples and the whole mass covered with a small section of a rubber tennis-ball held in place by strips of surgeon's plaster. The rubber covering tended to prevent the drying out of the moisture in the paste, which would change the conductivity of the system. Over each rubber cover was placed a pad of absorbent cotton and one or two large elastic bandages to provide a uniform pressure upon the electrodes. The leather belt over the pulleys of the treadmill developed con- siderable static electricity. Furthermore, leakage from the 220-volt system used in driving the treadmill caused considerable difficulty and was a constant source of danger to the delicate string of the galvanome- ter. At first, use was made of the method employed by Benedict and Murschhauser 1 of grounding the treadmill by means of small sections of brass chain trailing over the surface of the leather belt, the chains being connected to a rod and attached to a water-pipe in the laboratory. Later the use of the brass chain was discontinued and it was replaced by a roll of fine brass gauze which bore upon the full width of the leather belt. (See W and TFi, fig. 1, p. 19.) Under thjese conditions it was possible to obtain a record of the pulse-rate with the subject walking and wearing rubber-soled shoes. As at times difficulties would develop unexpectedly, this method was also abandoned, and instead of grounding the treadmill, it was arranged to ground the subject. This was done by a third electrode similar to those already described, which was placed upon the abdominal wall and connected to a water-pipe in the laboratory. (See V, fig. 1, p. 19.) The new method gave excellent results and enabled the subject to walk on the treadmill with ordinary shoes without disturbing the delicate string of the galvanometer. Benedict and Murschhauser, Carnegie Inst. Wash. Pub. No. 231, 1915, p. 37. 36 METABOLISM DURING WALKING. TECHNIQUE FOR SECURING RECORDS OF THE PULSE-RATE. The electrodes in the moist kaolin paste were put in position as pre- viously described, one above the right nipple and the other somewhat lower down on the left side, and fastened in place by means of adhe- sive tape and elastic bandages. The grounding electrode was fas- tened to the body near the umbilicus in a similar manner. The leads were then tested for response and for any fault in the grounding of the subject. At the beginning of the period, a signal was given to the operator in the galvanometer room and within a minute of the begin- ning of the experimental period a photographic pulse-record for ap- proximately 60 seconds was made. In the course of 3 or 5 minutes another record was taken, and a third at about the end of the tenth minute. Thus, during a 12-minute period, three records were ob- tained at approximately regular intervals. To obtain the pulse-rate per minute, the time and pulse-rate were subsequently counted by two assistants independently from these records and the average of the three records was taken as representative of the pulse-rate during the period. If, in any instance, difficulty was experienced in counting the records, or if the two assistants failed to agree in their counts, another count was made by a third individual. In some cases, owing to technical difficulties, it was possible to use only a portion of the record for the final count. DETERMINATION OF THE BODY-TEMPERATURE. Records of the body-temperature were secured in the rectum by means of an electrical resistance thermometer. The resistance coil em- bedded in Woods metal 1 in a pure-silver tube was provided with leads 10 meters long connecting the thermometer with a d'Arsonval galvano- meter and Wheatstone bridge placed in one corner of the room. Two of these rectal thermometers, each having a resistance of about 12 ohms, were used during the study. The apparatus was calibrated at tempera- tures of from 35 to 39 C. at intervals of 0.25 to 0.5 by immersing the thermometer bulb in a Dewar flask. These temperatures were read from a standard Richter mercurial thermometer, with an accuracy of 0.01 C. From the points thus obtained, curves were constructed from which temperatures to 0.01 C. were secured. These curves were checked at frequent intervals during the course of the study, to make sure that no change had taken place in the value of the resistance thermometers. Before the experiment of the day began, the thermometer was in- serted in the rectum of the subject to a definite depth, with the aid of a slight coating of mucochondrin. The leads were fastened to the buttocks by means of a small piece of adhesive tape to prevent any displacement of the thermometer as the subject walked. They were and Soderstrom, Arch. Intern. Med., 1915, 15, p. 820. METHODS OF MEASUREMENT. 37 then passed between the legs and out through the fly of the walking suit worn by the subject. The pointer on the dial of the Wheatstone bridge was placed upon the 100 division-mark of the slide-wire and a balance obtained with the compensating leads by an adjustable resist- ance inserted between the galvanometer and the bridge. The com- pensating leads were then replaced by the leads in the circuit of the thermometer. At first the temperature records were secured at the beginning and end of the periods, but after a few days they were taken oftener, usually every 2 minutes, and sometimes every minute. Read- ings were also made hi the intervals between the periods. Balances with the compensating leads were made at intervals during the forenoon. Between the periods, especially when the subject had been walking, he was allowed to sit on a stool placed on the treadmill or to stand erect. In either case it became necessary for his comfort to throw a blanket around him. It was found that if the blanket in- closed a portion of the leads (ordinary lamp cord), the balancing became extremely difficult; consequently, care was exercised to prevent more than 12 to 18 inches of the leads from being inclosed within the folds of the blanket. It was also observed at times that sitting affected the temperature reading, this being due, possibly, to a change in position of the thermometer within the walls of the rectum. These conditions were hard to avoid, but at all times the greatest care possible was used in insetting the thermometer to a uniform depth and in balancing with the compensating leads at frequent intervals. On a few days, when W. K. was doing a large amount of work, the weather was warm and an electric fan was allowed to blow a current of air across his face and shoulders. Except in these few experiments, the subjects walked hi the still air of the room, wearing heavier or lighter clothing in proportion to the amount of work which they were expected to perform. The effect of a moving air-current on the metabolism, general comfort, and efficiency of an individual has been emphasized by Hill in a recent report. 1 With the few exceptions stated above, we made no attempt to control the body-temperature of the subject, other than by keeping the room-temperature at approximately 20 C. and allowing the use of a blanket after the cessation of the exercise of walking. DETERMINATION OF THE BLOOD-PRESSURE. During the last month of the study, that is, subsequent to March 19, 1916, some determinations were made of the blood-pressure of E. D. B. as a part of the walking experiments. Attempts to record the blood- pressure while the subject was walking were unsuccessful, on account of the movements of the body. It was necessary, therefore, to make the measurements immediately after the walking had ceased. The 1 Hill, The science of ventilation and open air treatment, part I, Special Report, Ser. No. 32, Medical Research Committee, London, 1919. 38 METABOLISM DURING WALKING. apparatus used consisted of an Erlanger sphygmomanometer, with which a permanent record was secured on the kymograph. Only the systolic pressure, however, was noted. To assist in determining this point, we also employed a Nicholson sphygmomanometer, placing a cuff on the forearm and noting the first indication of the pulse from the movement of the Fedde* pith-ball. 1 The pressure was then read on the Erlanger sphygmomanometer. This double method of securing the systolic pressure was found to be more satisfactory under these special conditions than the use of a stethoscope on the brachial artery or placing entire reliance upon the tracing of the pointer on the Erlanger sphyg- momanometer. The cuffs were placed on the subject's right arm before the experi- ment began and were worn by him during the entire forenoon. In the standing experiments, three determinations were made as near to the second, sixth, and tenth minutes of each period as possible. In the walking experiments, the pressure was applied towards the end of the usual preliminary walk. When all was in readiness, the treadmill was stopped and two determinations of the systolic pressure were made as quickly as possible. The walking then began again immediately and the period commenced with but little loss of time, usually not more than 1 or 2 minutes. At the close of the period, while the subject was still walking, the pressure was again applied, and as soon as the tread- mill stopped a second series of records was secured. The average of these two observations, namely, the records after 10 minutes of pre- liminary walking, and after 10 or 12 minutes of walking in the period proper, are recorded as the blood-pressure for the walking period. It should be clearly understood, however, that these values were made while the subject was standing and 10 to 20 seconds after he had stopped walking. ROUTINE OF EXPERIMENTS. The approximate routine of an experimental period during a walking experiment was as follows: On the arrival of the subject at the Labora- tory, records were made of the last meal taken and the hour it was eaten to insure that the subject was in a post-absorptive condition. The electrodes for the pulse-record were then adjusted, and if the exercise was to be severe, a change was generally made to a walking- suit. The man was then weighed with clothing, after which the rectal thermometer was inserted. When the subject mounted the treadmill, a safety belt attached to the ceiling was buckled loosely about his waist. The counters for recording the number of steps and the step-lift were connected and read, also both of the revolution counters on the tread- mill. The subject then began the preliminary walking period. During this period a certain amount of air was withdrawn from the ventilating Diggers, Circulation in health and disease, Philadelphia and New York, 1915, fig. 53, p. 198. METHODS OF MEASUREMENT. 39 system and replaced by fresh oxygen, the absorbing bottles were weighed, and the system was tested for tightness. Approximately 2 minutes before the beginning of the walking period proper, the mouth- piece and nose-clip were adjusted. A signal was sent to the operator in the room where the pulse-rate was measured, and in quick succession readings were made of the ventilation adder, the oxygen meter and its temperature, the barometer, and the respiration counter, these readings being verified by a second observer. The kymograph on which the respiration was recorded was also started and the pens were adjusted. The walking period proper began when the subject was connected with the ventilating current of air by the opening* of the valve at the end of a normal expiration and coincident with the starting of a stop- watch and the reading of the "continuous counter." Within the next 30 seconds, the by-pass B (fig. 1, p. 19) was turned, the kymo- graph was started, which gave a record of the height of the steps, and the step-counter and height-counter were read at 1 minute and 1 min- ute and 10 seconds, respectively. During the period that followed, the operators were occupied in admitting oxygen, recording the body- temperature and pulse-rate, resetting the valve-operating device in reaoliness for the end of the experiment, adjusting or replacing the kymograph-drum of the step-lift record every 3 minutes, and weighing and testing the carbon-dioxide absorbers for the next period. At about 9 minutes after the period began, the efficiency of the carbon- dioxide absorbers was tested by deflecting a portion of the air-current through a solution of barium hydroxide. At the eleventh minute of the period the step-counter was read; at 11 minutes and 10 seconds, the step-lift counter was likewise read and a warning signal sent to the operator in the pulse-record room. At approximately the twelfth minute, the valve was turned at the end of a normal expiration, a simultaneous reading of the "continuous counter" was made, and the period ended. Readings of the various counters were recorded, and when the carbon dioxide in the system had been completely absorbed, oxygen was admitted to bring the spirometer-bell to its original level. Finally, records were made of the oxygen-meter and its temperature and of the barometer. Other periods followed with similar routine; between the periods the subject either sat, stood, or continued walking. During the interval between the periods, if the subject sat or stood, it was usually consid- ered advisable to throw a blanket over his shoulders and around the body, as previously described, for ordinarily he was warm and per- spiring freely after the muscular exercise of walking. Measurements were, as a rule, made in four to six periods during the forenoon. At the end of the morning the subject was released from the treadmill and weighed a second time. A typical record-sheet for one period of a walking experiment, with the necessary corrections and calculations, is given in table 2. 40 METABOLISM DURING WALKING. Snfcject, B.D.B. TABLE 2. Typical record of walking experiment. Bate, February 2, 1916. Grade, 25 p. ct. Last aaal, 7 p.m.: Lamb broth, roast beef, maahed potatoes, squash, three slices bread and butter, apple pie. Body-weight, with clothing: 9U5 a.m. 61.53 to;. ItOO p.m. 61.00 leg. Average 61. 27' leg. Period I. Began walking, 10:00:00 a.m. Period began, 10:13:20 a.m. Air-current used - 100 liters per minute. Duration of period, 12 min. 22-3/5 sec. or 12.387 min. Carbon dioxide. Absorbers BB v (End < Start (Difference Absorber 900 Total C0 2 lister. Temperature End 654.60 liters 18.0* C. Start 834.12 liters 17.8* 0. Difference 20.48 liters Av.l79* C. Valve correction 0.09 j.lter Corrected meter 20.57 liters Barometer 772.4 mm. Correction for temperature 2.7 mm. 769.7 ran. 900 Log. 0.5091 Log. total C0 2 Log. volume COg Difference 5&S =: 4.28 gms. 9.70680 - 10 1.52757 1.23417 17.15 liters. . Barometer Barometer temp. 772.1 inn. 21.4* C. Valve correction. Start +2 nm. 772.6 mm. 21.1^ 0. 772.4 am. 21.3* C. Diff . +2 mm. " * > ' 9 1U * r ' Log. meter factor 0.00294 Log. reduction to 0' C. Uj&J 9.97237 - 10 Correction for aqueous vapor at 17.9* 0. Corrected barometer 15.2 mm. 754.5 mm. Log, reduction .to 760 mmJ'^ -J 9.99685 - 10 Log. corrected meter 120.87 liters ) 1.31323 Los. volume 2 1.23539 = 19.29 liters Besniratory quotient. Log. volume C0 2 1.23417 Log. volume 2 1.28539 Log. respiratory quotient 9.94878 - 10 0.39 Carbon dioxide per minute. Log. volume C0 2 in o.o. 4.23417 Log. time (12.387 min. ) 1.09272, Log. C0 2 per min. in o.O. 3.14145 C0 2 per min. 1385 o.c. Oxygen per minute. Log. volume 2 la o.o. 4.28539 Log. time (12.387 min. ) 1.09273 Log. 2 per min. In c.c. 3.19267 Og per min. 1558 c.c. Ventilation. Ventilation adder wheel. Start 0.00 End 85.75 Ho. of revolutions 83.75 x 4.9 liters 410.38 liters, Respiration rate. Counter. 410.38 12.387 min. 3S.13 liters per min. r 80.75 liters per min. (reduced). End 3249 Start 2974 Difference 275 275 12.387 min. 22.1 per min. METHODS OF MEASUREMENT. TABLE 2. Typical record of walking experiment (continued). Distance walked. End Start Revolutions of wheel Continuous counter. Period counter. Total distance preliminary to period, Preliminary. Period. 451 x 1.33 602 meters. 21216 21638 57037 20765 21216 56614 Distance per minute in period. lei 451 V 422 ____423, 422.5 x 1.33 ., 13 per min. 42T.5 J.<*.ob' nin. At end of 1 min. At end of 11 min. For 10 min. Time. 9:45 a.m. 9:55 a.m. 10:00 a.m. 10:05 a.m. 10:13 a.m. 10:16 a.m. 10:20 a.m. 10:23 a.m. Time. 9:56:30 a.m. 10:13:00 a.m. 10:15:00 a.m. 10:18:30 a.m* 10:23:30 a.m. Step counter. Beading. 91617 92047 430 x 2 860 steps or 86.0 steps per min. Step-lift At end of 1 min. 10 sec. At end of 11 min. 10 sec. For 10 min. Reading 64748.5 64852.9 104.4 z 0.393 meter = 41.0 meters or 4.10 meters per min. Bridge. 200 209 235 246 255 Beats. 73 136 66 133 Rectal temperature record. Temperature. 36,48' C. 36.62* 0. 37.02* C. 37.19* C. 37. 35 C. Remarks. Thermometer inserted. Standing. Started walking. Period began. Pulse record. Seconds . 61 64 30 59 Bate . Remarks . 71.8 Standing. Period began. 127.5 W&llclng. 132.0 Walking. 135.3 Walking. 131.6 average for walking. SUBJECTS. Eight subjects were used in this study of the effect of muscular work upon the metabolism, but the greater part of the material was collected with two men, E. D. B. and W. K. A general description of these subjects follows. The body-surfaces were obtained by means of the height-weight chart of the Du Boises. 1 Experiments were made with still another subject (T. J. L.), but as he found difficulty in breathing through the mouthpiece and the results obtained with him were ob- viously erroneous, the data have not been included in this report. A. J. 0. Born September 1884; age 30 years; height 180 cm.; nude weight 69.5 kg.; body-surface 1.88 sq. meters. Had previously served as subject in experiments at the Nutrition Laboratory. No trade or special training, but was of athletic build and with some experience as a professional ball-player. Discontinued experiments with him early in the research, as he was unreliable in his engagements. H. R. R. Born March 13, 1896; age 19 years; height 185 cm.; nude weight 70 kg.; body-surface 1.93 sq. meters. Student at Harvard University. Not especially interested in sports. Somewhat ungainly in movements and not "easy going" in his walk. Had a tendency to stoop and was of a nervous temperament. While he was anxious and willing to cooperate in every way, his duties at college made it difficult to use his services as much as would other- wise have been possible. *Du Boia and Du Bois, Arch. Intern. Med., 1916, 17, p. 863. 42 METABOLISM DURING WALKING. T. H. H. Born September 2, 1886; age 29 years; height 171 cm.; nude- weight 54.5 kg.; body-surface 1.63 sq. meters. Occupation, gardener. An Englishman, but recently arrived in this country, and without a situation. Served as subject but a few weeks, as he secured permanent work at his regular occupation. Slow and awkward in movements, but showed a desire to cooperate in the experiments. W. K. Born December 24, 1885; age 29 years; height 162 cm.; nude weight 49.2 kg.; body-surface 1.51 sq. meters. No trade, but had served as waiter in a restaurant. Satisfactory and reliable; during a part of the research the experiments were made with this subject only, as it was difficult to find suitable men. Stocky, well-built, easy walker, possessed a considerable amount of grit, and fulfilled each requirement to the best of his ability. E. D. B Born October 23, 1892; age 23 years; height 173 cm. ; nude weight 57 kg. ; body-surface 1.68 sq. meters. 1 Quiet and phlegmatic. Had lived in a country town, and though not athletic, was well-built and accustomed to walking. After a few months' service, he suffered from a strained tendon in his foot; his use as a subject was accordingly discontinued, until the lameness disappeared (January 6 to 30, 1916, inclusive). Examined on May 2, 1916, by a physician, who reported that "the heart sounds were of good quality; no murmurs heard; heart entirely normal." While E. D. B. was incapacitated, the standing and walking tests were continued by using volunteer subjects from the Laboratory staff, all of whom had assisted in the experiments. These men were : J. H. G. Born April 21, 1895; age 20 years; height 185 cm.; nude weight 68.0 kg.; body-surface 1.89 sq. meters. E. L. F, Born November 27, 1892; age 23 years; height 171 cm.; nude weight 70.4 kg.; body-surface 1.82 sq. meters. H. M. S. Born August 31, 1868; age 48 years; height 180 cm.; nude weight 60.4 kg.; body-surface 1.78 sq. meters. STATISTICS OF EXPERIMENTS. The statistical data obtained in this study appear in chronological order for each subject in tables 3 to 16a. Metabolism measurements were made on some 225 days in all, with a total of approximately 1,300 experimental periods. These experiments were all carried out in the forenoon, with the subject in the post-absorptive condition, i. e., ap- proximately 12 hours after the last meal. The experimental periods- were usually about 12 minutes in duration, except for the severer grades of walking, when the time was reduced to 10 minutes and, in a few instances, to 8 minutes. All of the results secured are given in the tables and represent the gross outlay in the energy output. With the exception of one day when the subject was psychically stimulated, no figures were excluded from the averages except in case of manifest error. Such exclusions have been indicated by inclosing the figures in parentheses. The averages for the different days are the averages of the results obtained for the *For additional data regarding surface area, see paper by Benedict (Am. Journ. Physiol., 1916, 41, p. 275) in which photograph, silhouettes, and measurements are given of E. D. B. as Sub- ject 7. STATISTICS OF EXPERIMENTS. 43 periods on the individual days, except in the case of the respiratory quotient and the heat-output, these two values being recalculated from the average carbon dioxide and oxygen. The total averages for the subjects were obtained by averaging the daily averages and not by averaging the data for the individual periods. TABLE 3. Metabolism of A. J. 0. and H. R. R., standing, in experiments without food. (Values per minute.) Date. Average respira- tion- rate. Average pul- monary ventila- tion (reduced). Average pulse- rate. Carbon dioxide. Oxygen. Respira- tory quotient. Heat (com- puted). A. J. O. 1915. Feb. 15 ... 20.8 liters. 7.4 c. c. 242 c. c. 265 92 cals. 22.6 7.6 228 281 81 21.3 7.8 222 271 .82 Average. . . 21.6 7.6 231 272 .85 1.32 Feb. 24 20.2 7.8 235 270 .87 21.1 8.3 226 269 84 20.0 7.7 224 261 .86 20.7 7.9 227 265 .86 Average . . . 20.5 7.9 228 266 86 1 30 Feb. 27 23.3 8.0 223 268 84 23.3 8.0 215 276 .78 Average . . . 23.3 8.0 219 272 .81 1.31 Gen. av. (3 days) . . . 21.8 7.8 226 270 .84 1.31 H. R. R. 1915. Mar. 20 20.5 12.1 259 327 .80 21.0 11.5 107 230 310 .74 20.4 11.6 109 234 322 .73 Average . . . (20.6) (11.7) (108) (241) (320) (.75) (1.52) Apr. 10 16.6 8.1 99 247 306 .81 14.9 6.9 96 194 271 .72 15.1 7.1 95 212 270 .79 15.4 7.0 94 228 291 .79 15.1 7.0 91 225 295 .77 Average . . . 15.4 7.2 95 221 287 .77 1.37 Apr. 17 15.8 6.9 92 209 273 77 15.6 6.7 93 210 273 .77 15.2 6.5 210 272 .78 15.2 6.6 88 214 276 .78 Average . . . 15.5 6.7 91 211 274 .77 1.31 Gen. av. 1 (2 days) . 15.5 7.0 93 216 281 .77 1.34 'For Apr. 10 and 17, 1915. 44 METABOLISM DURING WALKING. TABLE 4. Metabolism of T. H. H., standing, in experiments without food. (Values per minute.) Date. Average respira- tion- rate. Average pul- monary ventila- tion (reduced). Average pulse- rate. Carbon dioxide. Oxygen. Respira- tory quotient. Heat (com- puted). 1915. Feb. 25 12.5 liters. 5.2 c. c. (217) c. c. 221 (0.98) cals. 12.9 5.0 199 227 .88 Average . . . 12.7 5.1 199 224 .89 1.10 Mar. 19 11.3 6.8 97 196 226 .87 13.5 7.5 200 243 .82 13.3 7.3 103 189 242 .78 Average . . . 12.7 7.2 100 195 237 .82 1.14 Mar. 22 13.1 7.2 87 201 224 .90 13.0 7.0 90 189 216 .88 13.6 7.3 96 196 223 .88 Average. . . 13.2 7.2 91 195 221 .88 1.08 Gen. av. (3 days) . . . 12.9 6.5 96 196 227 .86 1.11 TABLE 5. Metabolism of W. K., standing, in experiments without food. (Values per minute.) Date. Average respira- tion- rate. Average pul- monary ventila- tion (reduced) . Average pulse- rate. Carbon dioxide. Oxygen. Respira- tory quotient. Heat (com- puted). 1915. Feb. 26 21.3 liters. 7.0 c. c. 185 c. c. 209 0.89 cals. 23.1 6.7 179 214 .84 23.1 6.1 176 214 .83 Average. . . 22.5 6.6 180 212 .85 1.03 Mar. 11 20.3 5.5 78 170 (281) (.61) 20.9 5.8 80 168 235 .72 22.5 6.4 78 183 233 .79 Average . . . 21.2 5.9 79 174 234 .74 1.11 Mar. 12 27.0 6.7 186 225 .83 26.6 6.7 192 208 .93 21.1 7.8 201 207 .98 Average . . . 24.9 7.1 193 213 .91 1.05 STATISTICS OF EXPERIMENTS. 45 TABLE 5. Metabolism of W. K., standing, in experiments without food. (Values per minute.) Continued. Date. Average respira- tion- rate. Average pul- monary ventila- tion (reduced) . Average pulse- rate. Carbon dioxide. Oxygen. Respira- tory quotient. Heat (com- puted) . 1915 Mar. 13 22.5 liters. 6.3 c. c. 187 c. c. 264 71 cals. 24.1 8 2 211 262 81 24.5 7.7 201 234 86 Average 23.7 7.4 200 253 79 1.21 Mar. 16 20.3 7.2 81 182 203 90 18.2 5.6 177 212 84 18.6 5.7 187 222 85 Average . . . 19.0 6.2 81 182 212 .86 1.03 Mar. 17 17.1 5.6 87 187 261 72 18.1 5.8 82 186 253 74 19.2 5 6 77 196 (295) ( 67} Average . . . 18.1 5.7 82 190 257 .74 1.21 Mar. 18 18.2 8.8 80 176 212 83 18.2 9.1 81 177 212 84 18.1 9 84 179 213 85 Average . . . 18.2 9.0 82 177 212 .83 1.03 May 29 25.1 7 75 205 238 86 21.7 6 3 73 194 235 83 21 4 6 4 74 194 224 87 Average . . . 22.7 6.6 74 198 232 .85 1.13 June 1 . . 20 6 6 6 86 182 212 86 19 1 6 2 85 (266) 213 n 251 18.8 6.1 81 193 219 89 19.3 6.3 87 194 209 93 Average . . . 19.5 6.3 85 190 213 .89 1.05 June 2 20.2 9.8 81 191 224 85 22.8 10.7 78 189 236 81 21.1 10.2 181 233 78 Average.. . 21.4 10.2 80 187 231 .81 1.11 June 3 22 10 4 79 177 231 77 22.7 10.7 78 189 237 80 22.4 10 6 79 189 238 80 Average . . . 22.4 10.6 79 185 235 .79 1.13 June 4 20 4 9 6 177 218 82 19.7 9.6 189 241 79 23.6 10.6 74 183 238 77 Average. . . 21.2 9.9 74 183 232 .79 1.11 46 METABOLISM DURING WALKING. TABLE 5. Metabolism of W. K., standing, in experiments without food. (Values per minute. ) Continued. Date. Average respira- tion- rate. Average pul- monary ventila- tion (reduced) . Average pulse- rate. Carbon dioxide. Oxygen. Respira- tory quotient. Heat (com- puted) . 1915 June 5 20.7 liters. 9.5 c. c. 181 c. c. 233 0.78 cah. 20.9 9.9 201 250 .81 22 10 3 199 247 81 Average . . 21.2 9.9 194 243 .80 1.17 June 14 . . 20.8 9.6 78 182 224 .81 19 8 9 3 176 209 .85 18 8 8 9 74 171 203 85 Average . . . 19.8 93 76 176 212 .83 1.03 Gen. av. (14 days) 21.1 1 6.5 79 186 228 .82 1.10 'March 18, and June 2 to 14, inclusive, omitted from average. TABLE 6. Metabolism of E. D. B., standing, in experiments without food. (Values per minute.) Date. Average respira- tion- rate. Average pul- monary ventila- tion (reduced) . Average pulse- rate. Carbon dioxide. Oxygen. Respira- tory quotient. Heat (com- puted). 1915. Oct. 4. 11.5 liters. 8 2 c. c. 204 c. c. 237 86 cala. 12.1 8 3 212 266 80 13.3 8.8 204 250 .82 Average . . . 12.3 8.4 207 251 .82 1.21 Oct. 6 13.2 8 4 191 240 80 12.9 8.5 197 247 .80 13.1 8.4 190 247 .77 12.1 8.3 201 250 80 12.8 8.3 192 237 81 Average . . . 12.8 8.4 194 244 .80 1.17 Oct. 8 13.3 8 3 190 239 80 13.4 8.2 192 235 .82 13.2 8.2 191 252 .76 14.7 8.6 190 245 .78 13.6 8.2 186 230 .81 Average . . . 13.6 8.3 190 240 79 1.15 Oct. 9 13.3 8 2 189 254 74 14.1 8.5 190 242 .79 14.5 8.7 190 253 75 Average . . . 14.0 8.5 190 250 .76 1.19 STATISTICS OF EXPERIMENTS. 47 TABLE 6. Metabolism of E. D. B., standing, in experiments without food. (Values per minute. ) Continued. Date. Average respira- tion- rate. Average pul- monary ventila- tion (reduced) Average pulse- rate. Carbon dioxide. Oxygen. Respira- tory quotient. Heat (com- puted) . 1915 Oct. 11 14 5 liters. 8 7 c. c. 199 c. c. 223 0.90 cats. 15 9 2 206 241 .85 15 2 9 2 197 230 .86 Average 14 9 9 201 231 .87 1 13 Oct. 13 14.4 8 2 172 225 .76 14.8 8 8 190 242 .79 14 8 9 191 238 .81 Average 14 7 8 7 184 235 78 1 12 Oct. 14 14.2 9 192 233 .82 14.4 9 189 235 .81 14 5 8 9 185 234 .79 Average. . . 14.4 9.0 189 234 .81 1.13 Oct. 15 13 9 8 6 183 231 .79 15 3 9 4 187 231 .81 15.2 9.2 181 228 .80 Average 14.8 9 1 184 230 .80 1.10 Oct. 16 14 3 8 7 187 222 .84 15 9 9 4 188 211 .89 15.2 9.2 192 219 .88 Average 15.1 9 1 189 217 .87 1 06 Oct. 18. 15 9 4 204 238 .86 15.2 9.3 188 225 .84 14.9 9.2 196 224 .88 Average 15 9 3 196 229 .86 1 12 Oct. 19 16.0 9.3 190 235 .81 15.5 9.2 188 246 .77 15.8 9 4 191 236 .81 Average . . . 15.8 9.3 190 239 .80 1.14 Oct. 20 16.0 9.6 196 240 .82 16.1 9.4 186 222 .84 16 5 10 202 240 .84 Average. . . 16.2 9.7 195 234 .83 1.13 Oct. 21 15.3 9.1 185 220 .84 16.0 9.6 194 232 .84 16 2 9 5 189 216 .88 Average . . . 15.8 9.4 189 223 .85 1.08 48 METABOLISM DURING WALKING. TABLE 6. Metabolism of E. D. B., standing, in experiments without food. (Values per minute. ) Continued. Date. Average respira- tion- rate. Average pul- monary ventila- tion, (reduced) . Average pulse- rate. Carbon dioxide. Oxygen. Respira- tory quotient. Heat (com- puted). 1915 Oct. 22 16 6 liters. 9 7 c. c. 196 c. c. 222 0.89 cats. 15 8 9 2 180 213 85 16 9 3 185 216 .86 16 1 9 4 187 217 86 1 06 Oct. 23 15.4 8.8 177 218 .81 16 9 4 188 227 83 16 4 9 6 187 221 85 Average 15 9 9 3 184 222 .83 1.07 Oct. 25 15 7 9 2 196 214 92 16 5 9 7 194 213 92 16.0 9.5 196 227 .87 Average . 16.1 9 5 195 218 .90 1.07 Oct. 26 17 1 9 5 189 217 .87 16.1 9.4 186 212 .88 16.4 9.6 183 224 .82 Average. . 16.5 9 5 186 218 .85 1.06 Oct. 27 15.4 8.9 181 226 .80 16.7 9.4 181" 216 .84 15.6 9.2 182 224 .81 Average . . . 15.9 9.2 181 222 .82 1.07 Oct. 28 15.4 8.8 182 215 .85 15.6 9.2 187 229 .82 15.7 9.3 194 224 .87 Average . . . 15.6 9.1 188 223 .84 1.08 Oct. 29 15 2 8 6 180 219 82 15.8 9.1 188 228 .83 15.4 8.9 186 229 .81 Average. . . 15.5 8.9 185 225 82 1 09 Nov. 18 14.4 6.1 183 207 88 14.8 6.3 182 206 .89 14.6 6.2 181 205 .88 Average . . . 14.6 6.2 182 206 .88 1.01 Nov. 19 14.2 6.1 190 211 90 15.3 6.3 177 208 .85 14.7 6.4 180 207 .87 Average . . . 14.7 6.3 182 209 87 1.02 STATISTICS OF EXPERIMENTS. 49 TABLE 6. Metabolism of E. D. B., standing, in experiments without food. (Values per minute.) Continued. Date. Average respira- tion- rate. Average pul- monary ventila- tion (reduced). Average pulse- rate. Carbon dioxide. Oxygen. Respira- tory quotient. Heat (com- puted). 1915. Nov. 27 15.4 liters. 8.9 c. c. 199 c. c. 216 0.93 Cain. 16.1 9.4 222 16.0 9.4 208 224 .93 Average . . . 15.8 9.2 204 221 .92 1.09 Nov. 29 16.7 9.3 82 188 219 .86 16.8 9.4 188 213 .89 16.6 9.6 198 225 .88 Average. . . 16.7 9.4 82 191 219 .87 1.07 Nov. 30 16.5 9.4 74 195 218 .90 16.1 9.3 192 223 .86 16.5 9.6 204 235 .87 Average . . . 16.4 9.4 74 197 225 .88 1.10 Dec. 21 14.7 8.7 187 194 .97 15.1 9.1 58 193 212 .91 14.6 8.8 191 214 .90 Average. . . 14.8 8.9 58 190 207 .92 1.02 Dec. 22 12.6 7.7 184 217 .85 12.9 8.2 195 219 .89 Average. . . 12.8 8.0 190 218 .87 1.07 Dec. 31 14.6 8.9 193 242 .80 15.4 9.8 71 218 263 .83 15 7 10.3 78 222 265 .84 Average . . . 15.2 9.7 75 211 257 .82 1.24 1916. Jan. 3 16.0 9.5 199 229 .87 15 9.5 222 262 .85 15.8 9.5 209 258 .81 Average . . . 15.6 9.5 210 250 .84 1.21 Jan. 4 14.1 8.8 198 236 .84 15.1 9.6 216 242 .89 15.8 10.2 223 253 .88 Average . . . 15.0 9.5 212 244 .87 1.19 Jan. 5 14 8 8 7 85 199 251 .79 15.6 9.4 80 210 249 .84 16.2 9.3 78 208 259 .80 Average . . . 15.5 9.1 81 206 253 .81 1.22 50 METABOLISM DURING WALKING. TABLE 6. Metabolism of E. D. B., standing, in experiments without food. (Values per minute.) Continued. Date. Average respira- tion- rate. Average pul- monary ventila- tion (reduced). Average pulse- rate. Carbon dioxide. Oxygen. Respira- tory quotient. Heat (com- puted). 1916. Jan. 31 15 4 liters. 9 95 c. c. 197 c. c. 232 85 cals. 14.6 9.0 89 198 247 .80 16.1 9.5 88 194 244 80 Average . . . 15.4 9.2 91 196 241 .81 1.16 Feb. 1 15 5 9 6 96 220 277 79 16.6 10.0 95 221 267 .83 16.9 10.1 93 217 261 .83 Average . . . 16.3 9.9 95 219 268 .82 1.29 Feb. 12 14 4 8 8 65 191 244 78 1 17 Feb. 14 14.9 9 2 77 196 240 .82 1.16 Feb. 15 16 2 10 1 79 207 261 .79 1.25 Feb. 16 15 5 9 4 205 255 80 1 22 Feb. 17 16 5 10 85 210 267 79 1 28 Feb. 18 15.7 9.5 76 205 264 .78 1.26 Feb. 19 13.3 8 2 52 208 243 .86 1.18 Feb. 21 15.7 10 78 225 268 .84 1.30 Feb. 22 15 7 10 76 217 245 .89 1 20 Feb. 23 15 8 9 5 73 214 288 74 1 36 Feb. 24 15.0 9.5 73 214 254 .84 15.4 9 8 76 216 255 .85 Average . . . 15.2 9.7 75 215 255 .84 1.24 Feb. 25 15.8 9.4 71 208 238 .87 16.1 9.7 71 210 258 .81 Average. . . 16.0 9.6 71 209 248 .84 1.20 Feb. 26.. 15 7 9 1 67 212 244 .87 16.5 9.7 72 212 258 .82 Average . . . 16.1 9.4 70 212 251 .84 1.22 Feb. 28.. 14.4 9.0 225 239 .94 15.2 8.9 68 206 238 .87 15.6 9.5 70 209 255 .82 Average . . . 15.1 9.1 69 213 244 .87 1.19 Feb. 29 15.0 9 69 182 225 81 14.3 8.4 66 183 229 .80 15.1 9.0 69 185 237 .78 Average. . . 14.8 8.8 68 183 230 .80 1.10 Mar. 1 14 6 8 8 198 222 89 14.5 9.1 202 234 86 14.0 8.7 197 238 83 Average. . . 14.4 8.9 199 231 .86 1.13 STATISTICS OF EXPERIMENTS. 51 TABLE 6. Metabolism of E. D. B., standing, in experiments without food. (Values per minute. ) Continued. Date. Average respira- tion- rate. Average pul- monary ventila- tion (reduced) . Average pulse- rate. Carbon dioxide. Oxygen. Respira- tory quotient. Heat (com- puted). 1916. Mar 2 15 7 liters. 9 3 78 c. e. 202 c. c. 236 0.86 cab. 16 1 9 4 78 192 239 .81 14.9 9 80 198 244 .81 15 5 9 81 187 229 .82 16.0 9 2 82 185 15 3 9 2 76 192 243 .79 Average . . . 15.6 9.2 79 193 238 .81 1.15 Mar. 3 15 8 7 76 186 240 .78 15 7 9 3 74 194 244 .80 16 1 9 5 76 197 241 82 15 9 9 3 71 191 246 78 15.8 9 2 76 185 233 .80 15 9 9 2 73 186 241 .78 Average . . . 15.7 9.2 74 190 241 .79 1.15 Mar. 20 14.8 9 4 80 219 276 .80 16 9 8 82 215 272 .79 16 4 9 6 81 206 259 80 Average . . . 15.7 9.6 81 213 269 .79 1.29 Mar. 22 15 6 9 83 201 248 .81 16.5 9.4 81 206 255 .81 16.2 9.2 79 201 258 .78 Average . . . 16.1 9.2 81 203 254 .80 1.22 Mar. 23 16 1 9 2 77 201 249 81 15.9 9.0 73 196 251 .78 16.1 9.0 73 196 252 .78 Average. . . 16.0 9.1 74 198 251 .79 1.20 Mar. 24 16 2 9 1 77 216 242 89 16.6 9.7 76 216 264 .82 15.9 9 1 74 200 256 .78 Average . . . 16.2 9.3 76 211 254 .83 1.23 Mar. 29 15.4 8.9 79 201 255 .79 15.9 9.2 82 200 267 .75 16.1 9.4 83 204 272 .75 Average . . . 15.8 9.2 81 202 265 .76 1.26 Mar. 30 16.5 9.4 84 200 243 .83 15.8 9.1 83 198 251 .79 16.5 9.6 83 200 251 .80 Average . . . 16.3 9.4 83 199 248 .80 1.19 52 METABOLISM DURING WALKING. TABLE 6. Metabolism of E. D. B., standing, in experiments without food. (Values per minute. ) Continued. Date. Average respira- tion- rate. Average pul- monary ventila- tion (reduced) . Average pulse- rate. Carbon dioxide. Oxygen. Respira- tory quotient. Heat (com- puted) . 1916. Mar. 31 15 9 liters. 9 1 79 c. c. 201 c. c. 242 0.84 cals. 16 5 9 5 81 202 256 .79 16 2 9 4 78 193 243 .80 Average. . . 16.2 9.3 79 199 247 .81 1.19 Apr. 1 16 2 9 82 199 238 .84 16.4 9.4 80 198 235 .85 16.7 9.4 79 194 241 .81 Average . . . 16.4 9.3 80 197 238 .83 1.15 Apr. 3 15 2 Q Q 77 212 248 86 15.9 9.3 75 205 245 .84 15 8 9 3 76 201 247 .81 Average.. . 15.6 9.3 76 206 247 .83 1.19 Apr. 4 15 4 9 2 84 200 237 84 15.5 9 81 194 224 .87 15.9 9.3 85 195 239 .82 Average.. . 15.6 9.2 83 196 233 .84 1.13 Apr. 5 11 7 91 91 OO9 247 82 15.7 9.1 90 188 239 .79 16.3 9.3 90 194 250 .78 Average . . . 15.9 9.2 90 195 245 .80 1.18 Apr. 6 1 R 1 9n M 9fi7 OK7 70 15.7 9.2 86 195 238 .82 16.3 9.4 83 196 237 .83 Average. . . 15.7 9.2 86 198 244 .81 1.17 Apr. 7 14 8 8 8 79 1 SH 238 78 14.9 8.9 79 200 246 .82 15.4 9.0 82 194 242 .80 Average . . . 15.0 8.9 80 193 242 .80 1.16 Apr. 8 15 3 94 CM 99J. oe-i ftQ 15.2 9.0 79 204 241 .85 15.2 9.0 79 195 240 .82 Average.. . 15.2 9.1 80 208 244 .85 1.19 Apr. 10 14 8 Q ft Qfl 91J. 9QQ QO 15.4 9.3 82 216 237 .91 Average. . . 15.1 9.2 81 215 235 .91 1.16 STATISTICS OF EXPERIMENTS. 53 TABLE 6. Metabolism of E. D. B., standing, in experiments without food. (Values per minute.) Continued. Date. Average respira- tion- rate. Average pul- monary ventila- tion (reduced) Average pulse- rate. Carbon dioxide. Oxygen. Respira- tory quotient. Heat (com- puted). 1916. Apr. 11 15.1 liters. 8.9 84 c. c. 207 c. c. 228 0.91 cals. 14.8 8.9 77 202 241 .84 15.1 9.1 82 199 249 .80 Average . . . 15.0 9.0 81 203 239 .85 1.16 Apr. 12 15.5 9 1 86 200 245 .82 15.5 9.0 86 191 246 .78 15.6 9 4 79 202 270 .75 Average . . . 15.5 9.2 84 198 254 .78 1.21 Apr. 13 15.8 9 2 83 203 232 .88 15.6 9.2 82 201 233 .87 16.0 9 6 80 211 252 .84 Average . . . 15.8 9.3 82 205 239 .86 1.17 Apr. 14 15.1 9 80 218 246 .89 15.4 8 9 82 200 233 .86 15.8 9 2 82 204 235 .87 Average . . . 15.4 9.0 81 207 238 .87 1.16 Apr. 15 15.5 9 2 80 203 242 .84 15.9 9 3 81 201 235 .86 16.0 9.3 81 197 241 .82 Average . . . 15.8 9.3 81 200 239 .84 1.16 Gen. av. (71 days) 15.4 9.1 78 199 240 .83 1.16 TABLE 6a. Average body-temperature and blood-pressure of E. D. B., standing, in experi- ments without food. (Values per minute.) Date. Aver- age body- tem- pera- ture. Date. Aver- age body- tem- pera- ture. Blood- pres- sure. Date. Aver- age body- tem- pera- ture. Blood- pres- sure. 1916. Jan. 5 c. 36.89 1916. Jan. 31 C. 37.26 mm. 1916. Feb. 1 C. 37.29 mm. 36.94 37.22 37.27 36.89 37 19 37.19 Average . . . 36.91 Average . . . 37.22 Average . . . 37.25 Feb. 12 36.80 Feb. 14 37.10 54 METABOLISM DURING WALKING. TABLE 60. Average body-temperature and blood-pressure of E. D. B., standing, in experi- ments without food. (Values per minute.) Continued. Date. Aver- age aody- tem- pera- ture. Date. Aver- age body- tem- pera- ture. Blood- pres- sure. Date. Aver- age body- tem- pera- ture. Blood- pres- sure. 1916. Feb. 15 C. 36.94 36.88 37.13 37.21 36.36 37.01 36.94 37.25 1916. Mar. 20 C. 36.57 36.62 36.60 mm. 112 114 115 1916. Apr. 5 C. 37.00 36.91 36.95 mm. 119 118 117 Feb. 16 Average . . . Mar. 22 Average . . . Apr. 6 Feb. 17 TjVK IjS Feb. 19 36.60 114 36.95 118 TToK 91 Feb. 22 36.62 36.96 37.05 111 110 110 36.88 36.83 36.82 117 116 115 Feb. 23.. Average. . . Mar. 23 Average. . . Apr. 7 pvv, 04 36.94 36.95 Average . . . Feb. 25 36.88 110 36.84 116 36.95 37.11 37.08 37.09 113 113 115 36.62 36.41 36.45 118 120 120 Average . . . Mar 24 Average . . . Apr 8 37.06 37.07 Average . . . Feb. 26 37.09 114 36.49 119 37.07 37.49 37.23 37.27 117 121 121 36.66 36.65 36.69 122 127 126 36.99 37.02 Average . . . Mar. 29 .... Average . . . Apr. 10 Average . . . Feb. 28 37.01 37.33 120 36.67 125 36.67 36.75 36.81 36.84 36.63 36.68 106 111 111, 37.09 36.99 121 120 Average . . Feb. 29 Average . . . Mar. 30 Average . . . ATM. 1 1 37.04 121 36.74 36.72 109 36.85 36.82 36.84 118 116 119 36.76 36.64 36.69 37.03 37.09 37.08 111 115 113 Average. . . Anr 12 Average . . Mar. 2 Average. . Mar 31 36.84 118 36.70 36.53 36.59 36.50 36.62 36.62 36.68 37.07 113 36.99 36.98 36.89 118 117 118 36.64 36.59 36.77 119 122 118 Average . . A r.T- 1Q Average . . Mar. 3 Average . . Apr 1 36.95 118 36.67 120 36.94 36.91 36.93 115 118 117 36.78 36.75 36.68 113 115 118 Average . . Apr. 14 36.59 36.52 36.59 36.31 36.43 36.36 36.45 Average. . Apr. 3 36.93 117 Average.. 36.74 36.32 36.82 36.89 115 116 117 115 36.92 36.99 37.01 116 115 118 Average . . Apr. 15 Average.. Apr. 4 36.97 116 36.44 36.68 36.94 36.88 36.68 116 110 114 115 36.95 36.93 36.98 116 119 119 Average . . Gen. av. . Average. . 36.95 118 36.83 113 '36.89 2 117 'For 40 days. 2 For 20 days. STATISTICS OF EXPERIMENTS. 55 TABLE 7. Metabolism of J. H. G., E. L. P., and H. M. S., standing, in experiments without food. (Values per minute.) Date. Average respira- tion- rate. Average pul- monary ventila- tion (reduced). Average pulse- rate. Carbon dioxide. Oxygen. Respira- tory quotient. Heat (com- puted). J. H. G. 1916. Jan. 18 13.4 liters. 9.5 113 c. c. 225 c. c. 269 0.84 cals. 16.1 10.5 120 228 284 .80 17.7 11 5 243 310 .79 Average . . . 15.7 10.5 117 232 288 .81 1.39 Jan. 19 15.0 9.3 208 271 .77 16.2 10.3 106 191 262 .73 16.5 10.6 217 280 .78 Average . . . 15.9 10.1 106 205 271 .76 1.29 Jan. 20 16.6 11.0 102 226 278 .82 17.4 11.4 226 267 .85 17.5 11.5 109 222 285 .78 Average . . . 17.2 11.3 106 225 277 .81 1.33 Gen. av. (3 days) . . . 16.3 10.6 110 221 279 .79 1.34 E. L. F. Jan. 21 12.8 9.4 97 230 295 .78 16.8 10.7 100 219 293 .75 15.7 10.4 93 217 264 .82 Average . . . 15.1 10.2 97 222 284 .78 1.36 Jan. 22 11.8 9.8 241 269 .90 11.8 9 4 228 249 92 13.7 9 6 216 253 86 . 12 4 9 6 228 257 89 1 26 Jan. 24. 18.1 11.5 112 205 249 .83 17.2 12.0 119 220 250 .88 17.3 12 6 117 241 263 .92 Average . . . 17.5 12.0 116 222 254 .87 1.24 Gen. av. (3 days) . . . 15.0 10.6 107 224 265 .85 1.29 H. M. S. Jan 25 17.8 10.3 97 183 226 .81 17.0 9.9 97 179 248 .73 16.6 9.9 98 189 241 .79 Average. . . 17.1 10.0 97 184 238 .77 1.13 Jan 26 17.0 9 9 86 182 242 .76 16 4 9 9 87 184 237 78 16.8 10 1 86 186 224 .83 Average.. . 16.7 10.0 86 184 234 .79 1.12 Gen. av. (2 days) . . . 16.9 10.0 92 184 236 .78 1.13 56 METABOLISM DURING WALKING. TABLE 8. Metabolism of A. J. 0. and H. R. R. during horizontal walking in experiments without food. (Values per minute.) Date. Dis- tance. Aver- age respira- tion- rate. Aver- age pul- monary venti- lation (re- duced). Aver- age pulse- rate. No. of steps. Car- bon di- oxide. Oxy- gen. Res- pira- tory quo- tient. Heat (com- puted). A. J. O. 1915. Feb 15 meters. ^3 1 24 2 liters. 13.8 c. c. 585 c. c. 672 0.87 cals. 3.28 Feb 24 63.1 23 7 19.3 96.9 627 758 .83 3.67 63 8 24 5 14.9 96.8 619 750 .83 3.63 Average . 63 5 24 1 17.1 96.9 623 754 .83 3.65 Mar. 2 63.8 22 2 14.5 98.7 635 735 .87 3.58 60 7 22 5 14.0 93.8 584 694 .84 3.37 63.6 25.4 19.6 97.9 598 665 .90 3.27 Average .... 62.7 23 4 16.0 96.8 606 698 .87 3.41 Gen. av. (3 days) .... 63.1 23 9 15.6 96.9 605 708 .85 3.45 H. R. R. 1915. Mar. 20 67.7 18 1 16.8 115 105.4 812 1,017 .80 4.88 64.5 18.1 15.6 126 102.2 740 936 .79 4.48 Average .... 66.1 18.1 16.2 121 103.8 776 977 .80 4.69 Mar. 27 65.8 17 4 16.5 106 102.8- 756 888 .85 4.32 67.2 67.5 18.0 18.3 16.1 16.2 107 111 102.6 102.4 724 725 896 908 .81 .80 4.31 4.36 Average .... 66.8 17.9 16.3 108 102.6 735 897 .82 4.33 Apr. 3 60.9 15 5 15.0 104 95.2 694 837 .83 4.05 60.5 60.0 17.8 18.4 15.1 15.7 110 113 95.0 95.6 688 688 852 857 .81 .81 4.10 4.12 Average .... 60.5 17.2 15.3 109 95.3 690 849 .81 4.09 Apr. 10 61 1 17 9 16 101 99 718 887 81 4 27 Apr. 17 60.0 16 6 14.0 98.4 667 799 83 3.87 59.9 16.1 14.4 100 97.8 664 .83 2 3.87 Average 60.0 16.4 14.2 100 98.1 666 799 .83 3.87 Apr. 24 61 8 16 6 14 3 96 99 2 647 807 80 3 87 60.2 60.6 60.1 17.2 18.2 17.7 14.1 13.9 13.9 97 97 96 95.0 94.8 96.0 629 616 620 781 785 796 .81 .79 .80 3.76 3.76 3.82 Average .... 60.7 17.4 14.1 97 98.3 628 792 .80 3.80 Gen. av. (6 days) .... 62.5 17.5 15.4 106 99.5 702 867 .81 4.17 1 Computed from averages for Feb. 24 and Mar. 2. 'Computed from the carbon dioxide for the period and the respiratory quotient for the day. STATISTICS OF EXPERIMENTS. 57 TABLE 9. Metabolism of T. H. H. during horizontal walking in experiments without food (Values per minute.) Date. Dis- tance. Aver- age respira- tion- rate. Aver- age pul- monary venti- lation (re- duced) Aver- age pulse- rate. No. of steps. Car- bon di- oxide. Oxy- gen. Res- pira- tory quo- tient. Heat (com- puted). 1915. Feb. 25 meters. 63.4 liters. 12.6 100.7 c. c. 518 c. c. 624 0.83 cals. 3.02 63.7 15.9 11.5 98.3 546 602 .91 2.98 63 7 15.0 10.5 97.9 544 607 .90 2 99 Average. . . . 63.6 15.5 11.5 99.0 536 611 .88 2.99 Mar. 19 65 7 14.9 12.0 98 107.0 595 710 .84 3.44 66.7 67.1 67.8 16.8 16.7 15.3 11.7 11.5 11.4 103 106 108 106.4 106.2 106.0 571 562 561 715 733 713 .80 .77 .79 3.43 3.49 3.41 Average .... 66.8 15.9 11.7 104 106.4 572 718 .80 3.45 Mar. 22 67.5 14.4 11.0 97 106.6 582 722 .81 3.47 67.5 14.6 11.0 105.0 560 683 .82 3 30 Average .... 67.5 14.5 11.0 97 105.8 571 703 .81 3.38 Mar. 24 67 4 14 3 11 2 104 8 588 685 .86 3 34 68 1 14 4 11.2 104 2 574 (746) (.77) *3 22 67.8 13.2 11.0 88 103.6 574 652 .88 3.19 Average .... 67.8 14.0 11.1 88 104.2 579 669 .87 3.27 Mar. 26 65 9 15 3 11 6 88 100 8 613 671 92 3 32 67.6 68.2 14.2 13.5 11.0 10.3 88 84 101.2 102.0 572 555 (781) 646 (.73) .86 ^.IS 3.15 Average.. . . 67.2 14.3 11.0 87 101.3 580 659 .88 3.23 Mar. 30 65 9 13 8 12 102 607 683 .89 3 35 66 8 13 4 12 1 102.2 596 695 .86 3 39 63.5 14.4 11.7 93 99.8 560 675 .83 3.27 Average .... 65.4 13.9 12.0 93 101.3 588 684 .86 3.33 Apr. 5 62 4 13 2 11 3 99 99 4 593 690 86 3 36 62 7 13 1 11 1 101 100 4 575 13 35 63.2 13.8 11.2 105 100.8 577 709 .82 3.42 Average .... 62.8 13.4 11.2 102 100.2 582 700 .83 3.39 Gen. av. (7 days) .... 65.9 14.5 11.4 95 102.6 573 678 .85 3.30 Calculated from the carbon dioxide for the period and the average respiratory quotient for the day. 58 METABOLISM DURING WALKING. TABLE 10. Metabolism of W. K. during horizontal walking in experiments without food. (Values per minute.) Date. Dis- tance. Aver- age respira- tion- rate. Aver- age pul- monary venti- lation (re- duced) Aver- age pulse- rate. No. of steps. Car- bon di- oxide. Oxy- gen. Res- pira- tory quo- tient. Heat (com- puted). 1915. Feb 18 meters. 65.6 19.2 liters. 10.8 112.6 c. c. 431 c. c. 629 0.69 cols. 2.95 66 9 19 9 10 4 116 2 429 562 77 2 68 66.3 19.6 9.9 114.7 66 3 19 6 10.4 114.5 430 596 .72 2 80 Feb 26 64.4 19.9 9.7 114.7 435 528 .82 2.55 Mar. 4 64.0 21.4 14.8 115.4 (649) 621 (1.05) ^.oe 62.9 22 1 13 3 113.0 543 606 .90 2 98 66 21 13 1 115 2 561 625 90 3 08 64.3 21 5 13 7 114.5 552 617 .90 3 04 Mar. 5 65.3 20.6 11.9 115.3 532 596 .90 2.93 65.9 22.7 11.6 114.4 508 582 .87 2.84 66.2 23.8 11.8 115.2 505 593 .85 2.88 Average . . . 65.8 22.4 11.8 115.0 515 590 .87 2.88 Mar. 8 66.4 23.2 12 2 116.6 511 618 .83 2.99 66.6 26 8 12 9 116 498 590 .85 2.87 66.6 27 12 2 115 6 486 584 84 2 83 Average . . 66.5 25.7 12.4 116.1 498 597 .83 2.89 Mar. 9 66.0 24 1 11 1 115 6 533 615 .87 3 01 62.5 26.0 10.7 108.6 436 553 .80 2.65 62.2 24 2 10.2 109.0 433 1 2.57 58.6 23.7 11.2 107.6 421 511 .82 2.47 Average 62.3 24 5 10 8 110 2 456 560 81 2.70 Mar. 12 60.9 24.6 10.8 111.2 452 593 .76 2.82 58.5 25 10.4 109.8 431 512 .84 2.48 68.2 22.9 11.0 117.6 491 565 .87 2.76 Average. . . . 62.5 24.2 10.7 112.9 458 557 .82 2.69 Mar. 13 65.1 18.6 11.0 114.0 477 598 .80 2.87 64.7 18.7 10.6 113.0 455 583 .78 2.78 59.4 19.4 10.4 108 437 606 72 2.85 59.1 20 1 11 2 107 4 451 544 83 2.63 Average. . . . 62.1 19.2 10.8 110.6 455 583 .78 2.78 Mar. 16 59.2 21.3 11.1 74 109.8 461 558 .83 2.70 62.3 60.9 60.6 20.5 19.4 23.1 11.0 10.4 10.9 77 78 78 112.4 107.2 103.6 452 444 438 546 606 565 .83 .73 .78 2.64 2.86 2.69 Average .... 60.8 21.1 10.9 77 108.3 449 569 .79 2.72 'Average respiratory quotient for the day used in computing the heat-output. 2 Carbon dioxide for the period and average respiratory quotient for the day used in comput- ing the heat-output. STATISTICS OF EXPERIMENTS. 59 TABLE 10. Metabolism of W. K. during horizontal walking in experiments without food (Values per minute.) Continued. Date. Dis- tance. Aver- age respira- tion- rate. Aver- age pul- monary venti- lation (re- duced). Aver- age pulse- rate. No. of steps. Car- bon di- oxide. Oxy- gen. Res- pira- tory quo- tient. Heat (com- puted). 1915 Mar 17 meters. 67.3 22.1 liters. 11.4 75 117.2 e. e. 520 e. e. 614 0.85 cals. 2.99 67.4 67.8 67.5 24.8 22.3 22.8 11.5 11.4 11.3 73 77 116:8 116.2 114.6 502 487 493 564 572 565 .89 .85 .87 2.77 2.78 2 76 Average .... 67.5 23.0 11.4 75 116.2 501 579 .87 2.83 Mar 18 62.5 21.2 11.1 77 108.0 492 569 .87 2 78 58.4 60.8 58.8 20.7 22.6 19.7 10.2 10.5 9.9 74 77 78 100.0 106.2 104.2 443 448 432 537 532 526 .83 .84 .82 2.60 2.58 2.54 Average .... 60.1 21.1 10.4 77 104.6 454 541 .84 2.62 Mar. 23 64.3 20.5 12.0 83 111.6 456 (678) (.67) J 2.82 66.4 66 5 19.4 19 6 11.5 11 3 84 113.4 111 4 446 434 581 568 .77 76 2.77 2 70 Average 65.7 19.8 11.6 84 112.1 445 575 .77 2 74 Mar. 25 67.3 21.9 12.8 89 114.6 499 624 80 3 00 67.5 67.0 21.3 20.5 12.3 11.8 92 95 113.4 110.2 478 453 577 567 .83 .80 2.79 2.72 Average .... 67.3 21.2 12.3 92 112.7 477 589 .81 2.83 Mar. 29 63.3 18.8 10.2 94 109.0 426 539 .79 2.58 60.8 62.8 17.7 17.8 9.8 9.4 94 103 108.2 110.6 406 412 539 533 .75 .77 2.55 2.54 Average . . . 62. 3 18.1 9.8 97 109.3 415 537 .77 2.56 Mar. 31 64 8 18 8 10 2 85 108.2 454 530 86 2 58 65.8 10.2 85 109.8 448 X 2.59 64.8 64.9 18.7 20.1 10.1 9.9 84 86 109.6 107.6 438 425 525 516 .84 .83 2.55 2.50 Average . . . 65.1 19.2 10.1 85 108.8 441 524 .84 2.54 June 23 58 2 21 7 10 3 81 108.0 411 472 .87 2.31 57.1 56.0 20.5 20.7 10.1 9.9 72 72 106.0 105.4 385 383 473 455 .82 .84 2.28 2.21 Average . . . 57.1 21.0 10.1 75 106.5 393 467 .84 2.26 Gen. av. (16 days). .. 63.7 21.3 11.1 83 111.7 461 563 .82 2.72 1 Carbon dioxide for the period and average respiratory quotient for the day used in com- puting the heat-output. 60 METABOLISM DURING WALKING. TABLE 11. Metabolism of E. D. B. during horizontal walking in experiments without food. (Values per minute.) Date. Dis- tance Aver- age respira tion- rate. Aver- age pul- monarj venti- lation (re- duced) Aver- age pulse- rate. No. o: steps. Car- bon di- oxide. Oxy- gen. Res- pira- tory quo- tient. Heat (com- puted) . 1915. Oct. 9 meters 57.8 18.0 liters. 16.4 94.2 c. c. 534 c. c. 710 75 cals. 3.36 56 4 19.6 16.2 91.8 516 659 .78 3.15 Average 57 1 18.8 16 3 93.0 525 685 77 3.26 Oct. 11 56.3 19.5 17.6 89.0 535 610 .88 2.99 53 7 20.0 15.4 96.8 484 625 .77 2.98 Average . 55 19 8 16 5 92.9 510 618 83 2.99 Oct. 13 55.8 17.0 15.1 87.0 611 ^80 2.93 Oct. 14 55 3 19.5 16.7 88.4 462 585 .79 2.80 54 2 20 6 16 9 88.2 458 600 .76 2.85 54.1 20.2 16.8 . 87.8 467 612 .76 2.91 Average .... 54 5 20.1 16.8 88.1 462 599 .77 2.85 Oct. 15 55 4 18 6 16 4 88 9 470 575 .82 2.77 54.3 17.9 15.8 88.1 458 593 .77 2.83 53.6 15.5 14.8 89.4 469 609 .77 2.90 Average .... 54 4 17.3 15 7 88.8 466 592 .79 2.84 Oct. 16 65 2 16 3 16 5 98 539 600 .90 2 95 64.9 19.7 18.0 97.4 529 618 .86 3.01 65.0 17.6 16.6 97.6 511 633 .81 3.05 64.9 19.1 17.3 97.4 517 624 .83 3.02 Average .... 65.0 18.2 17.1 97.6 524 619 .85 3.01 Oct. 18 63 4 12 2 11 9 96 6 528 582 .91 2 87 64.5 15.2 12.9 97.2 538 615 .87 3.01 64.4 16.0 13.0 94.4 535 600 .89 2.95 64.8 17.0 13.3 97.4 539 614 .88 3.01 Average .... 64.3 15.1 12.8 96.4 535 603 .89 2.96 Oct. 19 64 6 15 9 12 7 97 522 591 .88 2 90 64.1 17.7 13.1 96.4 513 658 .78 3.14 63.9 18.3 13.0 96.4 499 617 .81 2.97 64.5 18.7 13.2 96.2 515 669 .77 3.19 Average. . . . 64.3 17.7 13.0 96.5 512 634 .81 3.05 Oct. 20 64.6 16 7 13.6 97.4 542 610 .89 3.00 64.4 17.8 13.7 97.0 537 647 .83 3.13 64.7 19.6 14.1 97.8 532 644 .83 3.12 64.5 20.3 13.9 97.8 523 645 .81 3.10 64.7 20.9 14.1 98.2 530 642 .83 3.11 Average .... 64.6 19.1 13.9 97.6 533 638 .84 3.09 1 Assumed. STATISTICS OF EXPERIMENTS. 61 TABLE 11. Metabolism of E. D. B. during horizontal walking in experiments without food- (Values per minute.) Continued. Date. Dis- tance. Aver- age respira- tion rate. Aver- age pul- monary venti- lation (re- duced). Aver- age pulse- rate. No. of steps. Car- bon di- oxide. Oxy- gen. Res- pira- tory quo- tient. Heat (com- puted.) 1915. Oct. 21 meters. 63.8 17.8 liters. 13.7 98.4 c. c. 544 c. c. 603 0.90 cola. 2.97 63.6 17.6 13.3 97.6 524 636 82 3.07 63.7 20.5 14.3 97.0 532 636 84 3 08 63 8 20 4 13 7 96.8 529 645 82 3 11 64 3 21 4 13 5 96.7 517 638 81 3 07 Average 63 8 19.5 13.7 97.3 529 632 84 3 07 Oct. 22 71.6 18.7 14.2 101.0 543 642 85 3.12 72.6 18.1 14.0 100.6 546 653 84 3.17 72.6 18.5 14.0 99.6 540 665 81 3.20 72.4 18 8 14 100.7 547 667 82 3.22 Average 72.3 18.5 14.1 100.5 544 657 83 3.18 Oct. 23 71.6 15.4 13.5 101.8 564 667 .84 3.23 72 4 18 3 14 3 101 555 674 82 3.25 72.2 18.6 13.9 100.6 542 662 82 3.19 72 6 19.4 14.2 100.8 544 675 81 3.25 Average 72.2 17.9 14.0 101.1 551 670 .82 3.23 Oct. 25. 72 5 17.6 14.3 101.4 562 637 88 3.12 72.9 15 6 13.5 101.1 551 665 83 3.22 73 18 3 14 2 101 4 546 670 81 3.22 73.7 17.9 14.0 101.4 545 673 81 3.24 73.7 18.1 14.0 101.4 547 679 81 3.27 Average . 73.2 17.5 14.0 101.4 550 665 .83 3.22 Oct. 26 72.5 16.4 13.1 103.0 516 657 .79 3.15 72.2 17.0 13.0 101.8 510 671 .76 3.19 73.5 19.3 14.0 102.4 529 680 .78 3.25 72.9 18.4 13.5 102.6 519 667 .78 3.19 73.2 18.7 13.7 102.2 521 677 .77 3.23 Average. . . . 72.9 18.0 13.5 102.4 519 670 .78 3.20 Oct. 27 76.6 19.0 14.4 104.2 557 663 .84 3.22 77.0 19.0 14.2 103.8 547 679 .81 3.27 77.3 18.9 14.2 104.4 553 687 .80 3.30 78.3 18.0 14.0 104.6 565 705 .80 3.38 78.5 18.0 14.0 105.0 561 709 .79 3.40 78.6 18.6 14.2 105.0 571 717 .80 3.44 Average . . . 77.7 18.6 14.2 104.5 559 693 .81 3.34 Oct. 28 77.1 17.5 14.4 106.6 594 654 .91 3.23 77.8 17.7 14.2 106.6 576 677 .85 3.29 77.8 19.3 14.6 105.8 568 688 .83 3.33 78.1 18.8 14.4 106.4 573 695 .83 3.36 78.2 17.8 14.1 107.2 566 682 .83 3.30 Average .... 77.8 18.2 14.3 106.5 575 679 .85 3.30 62 METABOLISM DURING WALKING. TABLE 11. Metabolism of E. D. B. during horizontal walking in experiments without food. (Values per minute.) Continued. Date. Dis- tance. Aver- age respira- tion rate. Aver- age pul- monary venti- lation (re- duced). Aver- age pulse- rate. No. of steps. Car- bon di- oxide. Oxy- gen. .Res- pira- tory quo- tient. Heat (com- puted). 1915. Oct. 29 meters. 77.1 16.8 liters. 13.9 68 104.4 c. c. 592 c. c. 689 0.86 cols. 3.36 78.1 78.3 78.5 19.5 19.3 20.9 14.5 14.5 15.4 77 88 93 106.1 104.4 104.4 570 577 597 688 704 723 .83 .82 .83 3.33 3.40 3.50 Average 78.0 19.1 14.6 82 104.8 584 701 .83 3.39 Oct. 30 45.2 16.7 11.1 80.0 429 496 .86 2.42 43.5 18.2 11.4 81.0 419 474 .88 2.32 43.1 18.5 11.1 79.8 401 484 .83 2.34 Average. . . . 43.9 17.8 11.2 80.3 416 485 .86 2.36 Nov. 1 44.9 17.4 11.4 79.2 434 471 .92 2.33 44.5 19.2 11.5 80.0 411 473 .87 2.31 43.5 18.0 11.2 79.8 406 478 .85 2.32 Average . . . 44.3 18.2 11.4 79.7 417 474 .88 2.32 Nov. 2 43.9 18.1 11.1 80.8 420 470 .89 2.31 43.4 19.2 11.3 79.4 412 483 .85 2.35 42.3 18.3 10.9 79.4 403 473 .85 2.30 Average . . . 43.2 18.5 11.1 79.9 412 475 .87 2.32 Nov. 3 45.4 18.6 11.1 80.8* 415 461 .90 2.27 44.7 18.6 11.0 80.0 398 469 .85 2.28 43.4 19.1 10.9 95.2 403 455 .89 2.23 Average .... 44.5 18.8 11.0 85.3 405 462 .88 2.26 Nov. 4 53.5 20.3 12.2 86.4 435 497 .87 2.43 53.2 21.2 12.3 86.4 431 502 .86 2.45 53.9 21.5 12.8 86.6 438 526 .83 2.54 Average .... 53.5 21.0 12.4 86.5 435 508 .86 2.48 Nov. 5 46.9 19.3 11.4 82.2 422 473 .89 2.32 46.2 45.6 20.2 20.0 11.2 11.5 63 68 81.8 81.6 400 398 478 479 .84 .83 2.32 2.32 Average .... 46.2 19.8 11.4 66 81.9 407 477 .85 2.32 Nov. 6 46.8 18.8 11.1 63 82.0 407 457 .89 2.24 45.8 45.0 19.1 18.9 11.0 10.9 67 71 80.8 79.6 405 402 458 462 .89 .87 2.25 2.26 Average .... 45.9 18.9 11.0 67 80.8 405 459 .88 2.25 Nov. 8 55.2 17.2 11.9 89 484 510 95 2.54 56.1 19.1 12.3 88.2 480 523 .92 2.59 57.0 19.8 12.3 89.8 474 525 .90 2.59 Average .... 56.1 18.7 12.2 89 479 519 92 2.57 STATISTICS OF EXPERIMENTS. 63 TABLE 11. Metabolism of E. D. B. during horizontal walking in experiments without food. (Values per minute.) Continued. Date. Dis- tance. Aver- age respira- tion- rate. Aver- age pul- monary venti- lation (re- duced). Aver- age pulse- rate. No. of steps. Car- bon di- oxide. Oxy- gen. Res- pira- tory quo- tient. Heat (com- puted). 1915. Nov. 9 meters. 54.9 20.1 liters. 12.3 88.8 e. e. 460 e. e. 486 0.95 eals. 2.42 54 5 21.6 12.5 87.6 448 (520) (.86) '2.41 54 6 21.0 12.3 87.6 452 498 .91 2.46 54.7 20.9 12.4 88.0 453 492 .92 2.43 Nov. 10 48.4 19.8 11.6 67 84.2 418 460 .91 2.27 47 8 21.0 11.8 85.2 411 476 .86 2.32 47 1 21 1 12.0 84.8 417 489 .85 2.38 Average .... 47.8 20.6 11.8 67 84.7 415 475 .87 2.32 Nov. 11 67.1 20.6 13.6 73 99.0 524 560 .94 2.78 68 2 21.9 18.3 98.8 524 608 .86 2.96 68 4 20 1 13.7 99.2 516 603 .85 2.93 Average., . . 67.9 20.9 15.2 73 99.0 521 590 .88 2.89 Nov. 12 66.0 19.8 13.6 81 99.2 528 573 .92 2.84 67.7 20.3 14.1 99.4 523 593 .88 2.91 67.6 21.4 14.3 98.8 530 592 .90 2.92 Average .... 67.1 20.5 14.0 81 99.1 527 586 .90 2.89 Nov. 13 76.1 19.6 14.5 78 104.2 584 608 .96 3.04 76.9 77 20.8 23 9 15.0 15.2 84 103.2 104.4 583 560 657 635 .89 .88 3.23 3.11 Average 76.7 21.4 14.9 81 103.9 576 633 .91 3.12 Nov. 15 76.3 19.6 14.4 87 103.0 606 631 .96 3.15 77 1 22 2 14.9 104.6 595 649 .92 3.21 77.5 21.3 14.8 104.4 581 645 .90 3.18 Average .... 77.0 21.0 14.7 87 104.0 594 642 .93 3.18 Nov. 16 76.4 20.3 14.4 76 102.8 563 654 .86 3.19 77.0 77.4 21.3 22.9 14.3 14.7 84 86 104.2 104.1 538 530 657 658 .82 .81 3.17 3.17 Average 76.9 21.5 14.5 82 103.7 544 656 .83 3.17 Nov. 17 46.2 20.4 12.2 81 79.0 404 470 .86 2.29 45.4 20.3 11.8 79.0 394 471 .84 2.28 45.6 21.2 12.3 79.0 400 473 .85 2.30 Average .... 45.7 20.6 12.1 81 79.0 399 471 .85 2.29 Nov. 18 55 7 19 9 12.3 90.8 424 507 .84 2.46 54.9 21.0 12.5 87.4 416 491 .85 2.39 54.6 21.7 12.6 87.4 423 511 .83 2.47 54.9 21.7 13.0 88.0 428 516 .83 2.50 54.7 21.8 13.0 87.8 436 518 .84 2.51 Average .... 55.0 21.2 12.7 88.3 425 509 .84 2.47 'Computed from the carbon dioxide for the period and the respiratory quotient for the day . 64 METABOLISM DURING WALKING. TABLE 11. Metabolism of E. D. B. during horizontal walking in experiments without food. (Values per minute.) Continued. Date. Dis- tance. Aver- age respira- tion- rate. Aver- age pul- monary venti- lation (re- duced). Aver- age pulse- rate. No. of steps. Car- bon di- oxide. Oxy- gen. Res- pira- tory quo- tient. Heat (com- puted.) 1915. Nov. 19 meters. 76 5 19 7 liters. 14 2 104 8 c. c. 532 c. c. 630 85 cols. 3 06 77.7 22.9 15.4 104.3 549 672 .82 3.24 77.9 22.6 14.7 103.0 529 665 .80 3.19 78.4 23.2 14.6 104.6 535 670 .80 3.22 78.9 23.8 14.9 104.0 546 676 .81 3.25 Average 77.9 22.4 14.8 104.1 538 663 .82 3.20 Nov. 22 48 20 12 82 2 422 484 87 2 37 47.3 20.1 11.8 80.2 416 486 .86 2.37 46.8 19.6 11.5 79.8 406 478 .85 2.32 Average .... 47.4 19.9 11.8 80.7 415 483 .86 2.35 Nov. 23 55 5 20 7 12 2 66 89 2 445 491 90 2 42 53.9 21.2 12.7 86.2 432 491 .88 2.41 54.9 21.5 12.5 87.8 440 495 .89 2.43 Average .... 54.8 21.1 12.5 66 87.7 439 492 .89 2.42 Nov. 24 57 7 21 6 13 2 90 4 460 490 94 2 44 57.6 21.8 13.3 89.6 447 500 .89 2.46 57.1 21.1 13.4 90.0 445 502 .89 2.47 Average .... 57.5 21.5 13.3 90.0 451 497 .91 2.45 Nov. 26 65.3 20.2 11.7 98 2 519 546 .95 2 72 66.2 19.8 11.6 99.2 527 559 .94 2.78 66.2 22.8 12.4 97.6 515 564 .91 2.78 Average .... 65.9 20.9 11.9 98.3 520 556 .93 2.76 Dec. 1 74 9 19 5 13 8 QO 101 599 697 96 3 13 76.4 77.3 21.0 21.6 15.0 15.0 87 87 104.8 106.2 599 575 657 647 .91 .89 3.24 3.18 Average .... 76.2 20.7 14.6 85 105.3 591 644 .92 3.19 Dec. 2 71 3 20 6 13 5 70 1O1 8 549 K7Q 95 2 8Q 71.8 71.8 21.4 22.2 14.1 13.7 81 82 101.8 101.8 539 522 596 585 .90 .89 2.93 2.87 Average .... 71.6 21.4 13.8 81 101.8 537 587 .91 2.90 Dec. 3 70 5 21 3 13 5 CO 1f)Q O 550 KQ7 92 2 95 71.2 72.1 22.3 23.1 13.5 14.3 86 101.1 101.3 532 526 605 609 .88 .86 2.96 2.97 Average .... 71.3 22.2 13.8 84 101.9 536 604 .89 2.96 Dec. 4 47 5 19 3 11 1 79 4 415 449 93 2 23 46.6 18.7 11.0 79.2 395 448 .88 2.20 45.9 19.2 12.1 78.4 394 459 .86 2.24 Average .... 46.7 19.1 11.4 79.0 401 452 .89 2.21 STATISTICS OF EXPERIMENTS. 65 TABLE 11. Metabolism of E. D. B. during horizontal walking in experiments without food. (Values per minute.) Continued. Date. Dis- tance. Aver- age respira- tion- rate. Aver- age pul- monarj venti- lation (re- duced) Aver- age pulse- rate. No. of steps. Car- bon di- oxide. Oxy- gen. Res- pira- tory quo- tient. Heat (com- puted). 1915. Dec. 6 meters. 45.2 18 liters. 10 5 63 78.8 c. c. 402 c. c. 440 91 cals. 2 17 45.1 44.7 18.7 19.5 10.2 10.6 67 67 78.4 78.2 383 384 450 441 .85 .87 2.19 2.16 Average . . . 45.0 18.7 10.4 66 78.5 390 444 .88 2.18 Dec. 7 43.8 19 1 10 8 75 78 8 413 453 91 2 24 43.1 50.6 19.9 20.8 11.1 11.8 79 81 77.2 75.2 410 424 445 484 .92 .88 2.20 2.37 Average .... 45.8 19.9 11.2 78 77.1 416 461 .90 2.27 Dec. 13 66 8 19 12 6 71 98 6 465 540 86 2 63 66.6 66.7 20.0 20.6 13.1 13.2 78 82 97.8 96.4 476 457 582 556 .82 .82 2.81 2.68 Average .... 66.7 19.9 13.0 77 97.6 466 559 .83 2.70 1916. Jan. 31 62 19 2 14 8 92 99 553 659 84 3 20 63.5 20.7 14.6 97.0 533 672 .79 3.22 63.4 63.9 21.5 21.4 14.2 14.2 105 94.4 93.4 534 532 688 673 .78 .79 3.29 3.22 Average .... 63.2 20.7 14.5 99 96.0 538 673 .80 3.23 Feb. 1 62 9 20 3 14 9 94 93 4 572 650 88 3 19 63.2 64.3 63.9 21.6 22.5 ' 21.5 13.9 13.6 14.2 97 97 99 94.4 94.8 94.0 518 492 521 642 614 646 .81 .80 .81 3.09 2.95 3.11 Average .... 63.6 21.5 14.2 97 94.2 526 638 .82 3.08 Mar. 20 59 5 21 2 18.1 514 604 85 2 94 60.7 22.8 18.4 509 581 .88 2.85 Average .... 60.1 22 18.3 512 593 86 2.89 Mar. 22 74 8 21 15 3 80 566 689 82 3 32 76 9 22 1 15 4 88 581 703 83 3 40 Average .... 75.9 21.6 15.4 84 574 696 82 3 36 Mar. 29 57 6 22 2 13 5 86 477 604 79 2 89 55.5 21 9 13.8 85 479 593 81 2 85 Average .... 56.6 22.1 13.7 86 478 599 .80 2.88 Mar. 30 68 5 18 15 2 83 584 681 86 3 32 63.6 23.3 15.8 82 532 622 85 3 02 Average .... 66.1 20 7 15 5 83 558 651 86 3 17 Mar. 31 55 2 21 7 15 4 68 512 539 95 2 69 52 9 21 2 12 8 77 507 552 92 2 73 Average .... 54.1 21.5 14.1 73 510 546 93 2 71 66 METABOLISM DURING WALKING. TABLE 11. Metabolism of E. D. B. during horizontal walking in experiments without food, (Values per minute.) Continued. Date. Dis- tance. Aver- age respira tion- rate. Aver- age pul- monary venti- lation (re- duced) Aver- age pulse- rate. No. of steps. Car- bon di- . oxide. Oxy- gen. Res- pira- tory quo- tient. Heat (com- puted). 1916. Apr. 1 < meters. 53.4 21.7 liters. 13.5 71 c. c. 472 e. e. 547 0.86 cala. 2.67 51.7 21.1 12.9 451 540 .83 2.61 50 4 21 3 12 3 80 445 536 .83 2.59 Average 51 8 21.4 12.9 76 456 541 .84 2.62 Apr. 3 35 1 19 3 11.7 68 401 443 .90 2.18 35 7 19 8 11 7 70 406 464 .87 2.27 36.7 18.8 11.0 75 391 464 .84 2.25 Average 35 8 19.3 11.5 71 399 457 .87 2.23 Apr. 4 35 9 19 4 11 6 69 395 475 .83 2.30 37.0 19.0 11.0 74 385 466 .83 2.25 37.0 18.9 10.8 73 378 488 .78 2.33 Average 36 6 19.1 11.1 72 386 476 .81 2.29 Apr. 5 77.4 21.4 19.7 87 598 732 .82 3.53 76.5 23.1 15.5 92 580 708 .82 3.42 79.3 22.7 15.8 96 600 726 .83 3.51 Average . 77 7 22.4 17.0 92 593 722 .82 3.48 Apr. 10 78.7 22.2 17.9 679 722 .94 3.59 77.1 24.0 19.4 88 654 722 .91 3.56 Average. . . 77.9 23.1 18.7 88 667 722 .92 3.57 Apr. 11 95.9 21.2 20.1 91 799 914 .87 4.47 92 24 3 19.7 99 743 845 .88 4.14 89.0 24.9 18.9 104 707 845 .84 4.10 Average. . 92 3 23 5 19 6 98 750 868 86 4 24 Apr. 12 89.2 22 9 18.8 86 731 901 .81 4.34 89 25.1 18.6 92 705 868 .81 4.18 86.6 23 3 17.6 677 840 .81 4 04 Average .... 88.3 23.8 18.3 89 704 870 .81 4.19 Apr. 13 99 7 24 4 20 9 95 819 928 88 4 55 97.7 23.5 20.2 102 812 942 .86 4.59 94.9 26 2 19.7 103 762 877 .87 4 29 Average .... 97.4 24.7 20.3 100 798 916 .87 4.48 Gen. av. (61 days) .... 62.2 20.3 14.0 81 93.0 508 595 .85 2.89 STATISTICS OF EXPERIMENTS. 67 TABLE lie. Average body-temperature and blood-pressure of E. D. B. during horizontal walking experiments without food. (Values per minute.) Date. Average body- tempera- ture. Blood- pressure. Date. Average body- tempera- ture. Blood- pressure. 1916. Jan. 31 C. 37.03 mm. 1916. Apr. 3 C. 36.86 mm. 124 37.20 37.12 123 37.34 37.31 121 37 42 37 10 123 Average 37 25 36 55 117 Feb. 1 37.05 36.73 118 37.21 36.84 118 V7 OQ 37.34 Average 36.71 118 Average 37.22 Apr. 5 37.06 37 23 123 Mar. 20 36.59 122 37.38 125 OC 70 19Q. 37 22 125 4 O AQ 199. Apr 10 36 95 129 Mar. 22 36.90 122 37.09 129 V7 nn 37 02 129 A Q QC ton, Apr 11 36 94 130 Mar. 29 36.91 124 37.29 129 37.00 125 37.43 129 Average 36.96 125 Average 37.22 129 Mar. 30 37.13 119 Apr. 12 36.95 130 37.17 117 37.28 07 qo 129 ion 37 15 118 37 19 130 Mar 31 36 86 37.14 127 Apr. 13 37.09 131 37 46 Average 37.00 126 37.62 131 Apr. 1 36 80 124 Average 37.39 131 37 17 123 Gen. av. . ... 1 37 07 *125 Average 37 00 124 15 days. *For 13 days. 68 METABOLISM DURING WALKING. TABLE 12. Metabolism of J. H. G., E. L. F., and H. M. S. during horizontal walking in experiments without food. (Values per minute.) Date. Dis- tance. Aver- age respira- tion- rate. Av'age pul- monary venti- lation (re- duced) Aver- age pulse- rate. No. of steps. Car- bon di- oxide. Oxy- gen. Res- pira- tory quo- tient. Heat (com- puted). J. H. G. 1916. Jan. 18 meters. 55 3 18 2 liters. 13 6 96 83.8 c. c. 578 c. e. 743 78 cats. 3 55 55.2 54.5 18.4 17.5 13.2 12.6 98 98 90.6 90.0 555 541 724 713 .77 .76 3.45 3.39 Average .... 55.0 18.0 13.1 97 88.1 558 727 .77 3.46 Jan. 19 55 3 17 7 13 7 89 88 9 553 689 81 3 31 55.1 19.7 17.3 105.2 538 721 .75 3.42 53.8 20.4 17.9 108.8 521 699 .75 3.31 Average .... 54.7 19.3 16.3 89 101.0 537 703 .76 3.34 Jan. 20 55 9 18 6 17 6 93 89 7 576 686 84 3 33 55.6 53.5 19.6 20.2 17.6 17.8 94 97 96.2 105.4 545 550 698 678 .78 .81 3.33 3.26 Average .... Gen. av. (3 days) 55.0 54.9 19.5 18.9 17.7 15.7 95 94 97.1 95.4 557 551 687 706 .81 .78 3.31 3.37 E. L. F. Jan. 21 52 5 16 18 87 90 6 638 804 80 3 85 52.3 52.5 18.1 19.4 13.9 14.2 86 90 90.4 89.8 549 541 711 715 .77 .76 3.39 3.40 Average 52.4 17.8 15.4 88 90.3 576 743 .78 3.55 Jan. 22 53 6 7 9 14 4 87 96 6 "618 688 90 3 39 52.5 52.3 6.2 6.4 13.1 13.1 92 93 93.2 580 589 703 683 .83 .86 3.40 3.33 Average .... 52.8 6.8 13.5 91 94.9 596 691 .86 3.37 Jan. 24 49 6 5 4 13 3 97 95 9 552 681 81 3 28 49.2 48.4 5.4 5.4 13.7 13.8 101 101 100.8 90.4 541 538 675 666 .80 .81 3.24 3.21 Average. . . . Gen. av. (3 days) .... 49.1 51.4 5.4 10.0 13.6 14.2 100 93 95.7 93.6 544 572 674 703 .81 .81 3.24 3.38 H. M. 8. Jan. 25 44 6 16 6 12.4 79 2 476 626 76 2 97 42.2 41.6 17.9 18.1 11.9 11.9 92 93 76.2 76.0 449 429 584 594 .77 .72 2.78 2.79 Average .... 42.8 17.5 12.1 93 77.1 451 601 .75 2.85 Jan. 26 53.5 15 4 12.7 90 4 525 665 79 3 18 52 7 17 3 12.7 77 2 495 647 77 3 07 52.3 19.3 12.8 88 83.2 479 644 .74 3.04 Average. . . . Gen. av. (2 days) 52.8 47.8 17.3 17.4 12.7 12.4 88 91 83.6 80.4 500 476 652 627 .77 .76 3.11 2.98 STATISTICS OF EXPERIMENTS. 69 TABLE 13. Metabolism of A. J. 0., and H. R. R. during grade walking in experiments without food. (Values per minute.) Date. Grade. Dis- tance. Aver- age respi- ration- rate. Aver- age pul- monary venti- lation (re- duced). Aver- age pulse- rate. No. of steps. Car- bon di- oxide. Oxy- gen. Res- pira- tory quo- tient. Heat (com- puted) . A. J. O. 1915. Mar. 2 p. ct. meters. 61.1 24.5 liters. 17.6 94.4 c. c. 749 c. c. 871 0.86 cols. 4.25 68.1 25.2 18.0 102 6 822 955 .86 4.66 Average 3.6 64.6 24.9 17.8 98.5 786 913 .86 4.45 H. R. R. 1915. Mar. 27 66.4 24.5 29.5 147 105.6 1,445 1,672 .87 8.17 66.4 26.8 29.5 105.4 1,398 1,687 .83 8.16 66 8 27.4 30.3 105.4 1,427 1,730 .83 8.35 66.6 30.3 31.8 104.8 1,458 1,727 .85 8.40 Average . . 10.6 66.6 27.3 30.3 147 105.3 1,432 1,704 .84 8.26 Apr. 3 .... 61 7 24.5 27.7 143 97 4 1,309 1,532 .86 7.47 61.9 25.0 28.1 98.8 1,308 1,553 .84 7.53 61.8 26.1 28.7 99.6 1,291 1,578 .82 7.61 62.2 27.4 30.5 102.6 1,339 1,634 .82 7.88 Average . . 10.2 61.9 25.8 28.7 143 99.6 1,312 1,574 .83 7.62 Apr. 24 63 8 23.3 25.9 130 100 6 1,255 1,502 .84 7.28 64.2 23.7 26.1 143 100.6 1,241 1,553 .80 7.46 64.1 24.0 26.3 144 102.0 1,239 1,532 .81 7.37 Average . . 10.5 64.0 23.7 26.1 139 101.1 1,245 1,529 .81 7.36 May 1 ... 71 8 23 4 29.8 132 108 2 1,466 1,667 .88 8.17 72.5 25.5 30.8 136 108.8 1,465 1,705 .86 8.31 73.1 26.5 31.8 142 108.6 1,484 1,741 .86 8.49 73.2 27.1 32.6 151 109.2 1,560 1,830 .85 8.90 73.0 27.9 33.3 163 107.8 1,547 1,834 .85 8.92 72.9 30.9 31.4 166 106.8 1,515 1,820 .83 8.81 Average . . 10.5 72.8 26.9 31.6 148 108.2 1,506 1,766 .85 8.59 May8 75.9 22.3 30.1 112.4 1,525 1,742 .88 8.54 76 1 23.9 31.1 112.0 1,534 1,777 .87 8.68 76 5 24 3 31.4 111.8 1,564 1,820 .86 8.87 76 7 24 7 32.5 112.0 1,589 1,855 .86 9.04 77 25 7 32.9 111.4 1,548 1,911 .81 9.20 77 26.6 34.1 111.2 1,593 1,913 .84 9.28 Average. . 10 5 76 5 24 6 32.0 111.8 1,559 1,836 .85 8.93 May 22 66.5 26.2 36.8 134 104.6 1,783 2,014 .89 9.89 66.3 27.2 36.9 148 106.6 1,735 2,028 .86 9.89 65.7 28.5 37.5 154 106.6 1,741 2,042 .85 9.93 66.3 29.0 39.0 164 108.4 1,787 2,077 .86 10.13 Average . . 15.3 66.2 27.7 37.6 150 106.6 1,762 2,040 .86 9.95 70 METABOLISM DURING WALKING. TABLE 14. Metabolism of T. H. H. during grade walking in experiments without food. (Values per minute.) Date. Grade. Dis- tance. Aver- age respi- ration- rate. Average pul- monary venti- lation (re- duced). Aver- age pulse- rate. No. of steps. Car- bon di- oxide. Oxy- gen. Res- pira- tory quo- tient. Heat (com- puted). 1915. Mar. 24 p. ct. meters. 63.4 15.9 liters. 16.7 114 97.4 c. c. 1,028 c. c. 1,136 0.91 cals. 5.61 62.3 16.5 17.3 120 98.0 1,017 1,173 .87 5.73 62.1 17.0 16.7 121 98.0 974 1,153 .85 5.61 Average . . 10.3 62.6 16.5 16.9 118 97.8 1,006 1,154 .87 5.64 Mar. 26 63.4 16.6 17.3 113 96.2 1,065 1,174 .91 5.79 64.3 16.7 17.5 117 100.6 1,067 1,196 .89 5.87 64.1 17.3 18.0 120 100.2 1,064 1,219 .88 5.97 63.9 17.8 18.0 126 96.6 1,046 1,251 .84 6.07 Average . . 10.3 63.9 17.1 ,17.7 119 98.4 1,061 1,210 .88 5.93 Mar 30 62.1 18.4 18.8 101.6 1,057 1,178 .90 5.80 61.0 19.2 18.8 117 99.8 1,011 1,166 .87 5.70 61.3 19.4 19.1 101.4 1,014 1,222 .83 5.91 Average . . 10.2 61.5 19.0 18.9 117 100.9 1,027 1,189 .86 5.80 Apr. 5 . . 62.3 17.9 18.4 126 103.4 1,056 1,241 .85 6.03 63.2 19.0 18.8 132 104.2 1,050 1,309 .80 6.28 63.7 18.8 18.9 102.8 1,039 1,339 .78 6.40 Average . . 10.4 63.1 18.6 18.7 129 103.5 1,048 1,296 .81 6.24 Apr. 6 . ... 58.4 17.6 17.5 118 99.0 1,019 1,135 .90 5.59 59.3 19.0 18.1 123 100.8 1,021 1,144 .89 5.62 60.2 19.0 17.9 125 100.6 1,012 1,167 .87 5.70 59.4 19.0 18.1 129 101.6 968 1,268 .77 6 04 60.1 20.0 17.9 136 103.2 1,006 1,231 .82 5.94 60.4 21.0 18.3 147 103.6 4,009 1,275 .79 6.11 Average . . 10.4 59.6 19.3 18.0 130 101.5 1,006 1,203 .84 5.83 Apr. 7 56.1 18.7 17.4 121 98.6 957 1,118 .86 5.45 56.4 18.8 17.7 118 100.4 953 1,130 .85 5 50 56.3 18.1 17.1 124 99.8 932 1,134 .82 5 47 56.6 18.4 17.0 133 100.6 941 1,152 .82 5.56 56.5 18.6 17.2 139 101.0 931 1,160 .80 5.57 57.2 17.9 17.2 146 103.6 968 1,207 .80 5 79 57.6 18 6 17.6 103.6 979 1,206 81 5 80 Average . . 10.4 56.7 18.4 17.3 130 101.1 952 1,158 .82 5.59 Apr. 8 67.8 18.6 19.3 105.4 1,115 1,300 86 6 34 68.0 19.4 19.7 105.6 1,089 1,277 86 6 23 67.5 19.9 19.7 104 8 1 088 1 308 83 6 33 67.9 20.8 20.3 103.2 1,100 1,322 .83 6 40 68.6 21.2 20.6 103.4 1,090 1,347 81 6 48 69.0 20.5 20.4 104.4 1,079 1,374 79 6 58 Average . . 10.4 68.1 20.1 20.0 104.5 1,094 1,321 .83 6.39 Apr. 16 63.9 14.2 16.7 100 101.4 972 1,178 83 5 70 65.0 15.5 17.0 102 100.0 1,011 1,204 84 5 84 64.8 17.0 16.9 104 99.2 992 1,196 83 5 79 65.0 17.7 16.6 107 100.6 981 1,204 82 5 81 65.4 18.1 17.5 116 101.6 985 1 232 80 5 91 65.9 18.8 17.7 119 101 998 1 245 80 5 98 Average . . 10.3 65.0 16.9 17.1 108 100.6 990 1,210 .82 5.84 STATISTICS OF EXPERIMENTS. 71 TABLE 15. Metabolism of W. K. during grade walking in experiments without food. (Values per minute.) Date. Grade Dis- tance. Aver- age respi- ration rate. Aver- age pul- monary venti- lation (re- duced) Aver- age pulse- rate. No. of steps. Car- bon di- oxide. Oxy- gen. Res- pira- tory quo- tient. Heat (com- puted). 1915. Mar. 4 ... p. ct. meters 69.5 24.0 liters. 16.9 114.8 c. c. 733 c. c. 810 0.91 cals. 4.00 68.9 24.8 15.7 113.5 691 770 .90 3.79 68.9 25.5 16.3 114.0 701 782 .90 3.85 Average 3.6 69.1 24.8 16 3 114 1 708 787 .90 3 88 Mar. 5 67.5 22.1 11.0 116.3 666 758 .88 3.71 68.3 23.0 13.5 116.0 643 763 .85 3.71 68.3 23.1 13.5 116.0 638 767 .83 3.71 68.4 22.8 13 1 114.2 625 775 .81 3.73 Average 3.6 68.1 22 8 12 8 115.6 643 766 .84 3 72 Mar. 8 68.9 22.7 14.9 118.2 678 790 .86 3.85 69.6 27.8 16.0 118.6 671 848 .79 4.06 70.1 28.3 16 6 117.6 688 812 .85 3.95 Average 3.9 69.5 26.3 15.8 118.1 679 817 .83 3.95 Mar. 9 .... 70.0 22.6 14 117.8 655 803 .82 3.87 70.5 27.9 14 8 117.6 652 802 .81 3.86 Average 3.9 70.3 25.3 14.4 117.7 654 803 .81 3.86 Mar. 23 63.2 23.7 20.2 110 108.2 872 1,004 .87 4.91 66.6 25.0 20 3 114 108 4 857 *4 81 63.2 26.1 20.2 117 109.4 871 1,024 .85 4.98 63.5 26.5 20 5 119 107.6 910 1,032 .88 5.06 Average . . 9.2 64.1 25.3 20.3 115 108.4 878 1,020 .86 4.97 Mar. 25.. . 60.9 23.6 19 5 120 104.6 861 1,028 .84 4.99 60.8 24.8 19 8 120 103 6 855 1,050 .82 5.07 60.8 25.0 20.0 128 100.8 856 1,042 .82 5.03 Average . . 10.7 60.8 24.5 19.8 123 103.0 857 1,040 .82 5.02 Mar. 31 58.3 24.7 18.3 113 104.0 837 978 .86 4.77 58.3 25.4 18 2 123 105.4 843 987 .86 4.81 58.2 25.1 18 2 125 103.4 835 995 .84 4.83 58.9 26.1 18 4 129 104.4 929 1,007 .93 4.99 Average . . 10.3 58.4 25.3 18.3 123 104.3 861 992 .87 4.85 Apr. 2 57.6 24.6 20 108 98.9 860 964 .89 4.74 57.9 57.9 58.8 58.7 58.6 57.7 24.4 24.9 25.0 25.1 24.5 25.1 19.8 19.6 20.1 17.9 17.8 19.2 108 112 112 116 115 99.6 100.0 100.6 101.6 99.8 99.0 817 812 846 825 802 816 981 1,105 988 1,098 1,005 992 .83 .74 .86 .75 .80 .83 4.75 5.22 4.82 5.20 4.83 4.80 Average . . 10.3 58.2 24.8 19.2 112 99.9 825 1,019 .81 4.90 'Computed from the carbon dioxide for the period and the average of the respiratory quotient* for the day. 72 METABOLISM DURING WALKING. TABLE 15. Metabolism of W. K. during grade walking in experiments without food. (Values per minute.) Continued. Date. Grade Dis- tance. Aver- age respi- ration rate. Aver- age pul- monary venti- lation (re- duced) Aver- age pulse- rate. No. of steps. Car- bon di- oxide. Oxy- gen. Res- pira- tory quo- tient. Heat (com- puted). 1915. Apr. 12 p. ct. meters 59.5 24.4 liters. 18.5 118 107.6 c. c. 833 c. c. 1,025 0.82 cals. 4.95 59.8 24.3 19.7 107.4 846 1,036 .82 5.00 59.1 25.3 18.0 106.0 798 1,014 .79 4.86 59.1 25.5 19.6 103.6 809 1,044 .78 4.99 57.9 24.5 17.2 126 101.8 815 1,029 .79 4.93 58.1 24.3 17.5 125 104.8 801 1,093 .74 5.15 58.0 23.9 18.9 130 107.2 806 1,022 .79 4.89 Average . . 10.5 58.8 24.6 18.5 125 105.5 815 1,038 .79 4.97 Apr. 13 . . 58.6 24.8 18.5 106.8 801 1,076 .75 5.10 58.2 24.4 18.0 105.2 814 982 .83 4.75 58.3 24.9 17.5 103.6 820 981 .84 4.76 10 5 58 4 24 7 18.0 105.2 812 1,013 .80 4 86 Apr. 14 63.9 26.3 21.8 112.0 931 1,041 .90 5.13 64.5 26.5 21.4 111.2 921 1.069 .86 5.21 64 5 27.1 21.2 110.0 902 1,051 .86 5 12 64 9 26.9 19.6 108.2 921 1,112 .83 5 38 65.0 26.5 19.6 106.6 900 1,073 .84 5.20 Average 10 5 64.6 26.7 20.7 109.6 915 1,069 .86 5 21 Apr. 16 64.1 26.2 18.7 112 106.4 904 1,063 .85 5.17 64.1 26.1 19.1 120 105.8 893 1,016 .88 4.98 64.4 26.8 19.2 125 107.4 ' 871 1,150 .76 5.46 64.1 26.7 18.7 130 108.4 871 1,045 .84 5 06 64.4 26.9 18.9 133 106.8 869 1,047 .83 5.07 64.9 27.0 18.7 137 108.0 858 1,077 .80 5.17 65.2 27.5 19.2 139 108.2 880 1,076 .82 5.19 Average . . 10.3 64.5 26.7 18.9 128 107.3 878 1,068 .82 5.15 Apr. 20 69.2 26.2 19.9 114 110.8 951 1,207 .79 5.78 69.6 26.8 19.6 118 111.0 943 1,217 .78 5 81 123 69.1 27.2 18.6 125 108.9 884 (1,374) (.65) *5 41 69.3 27.4 19.4 125 110.8 958 1,121 .86 5 46 69.2 27.5 18.8 127 110.8 879 (1,349) (.65) 5.38 69.7 27.4 18.6 131 112.6 906 1,277 .71 5 99 Average . . 10.5 69.4 27.1 19.1 123 110.8 920 1,206 .76 5.73 Apr. 21 70.0 27.1 22.6 106 111.2 946 1,158 82 5 59 70.0 27.0 21.8 111 111.4 931 1,226 .76 5 83 70.1 28.3 22.9 115 111.2 978 1,182 .83 5.72 71.6 28.2 22.3 112 112.4 940 (1,499) (.63) *5 59 72.0 29.4 22.9 113 111.8 966 1,154 .84 5.60 Average . . 10.5 70.7 28.0 22.5 111 111.6 952 1,180 .81 5.68 x Computed from the carbon dioxide for the period and the average of the respiratory quotients or the day. STATISTICS OF EXPERIMENTS. 73 TABLE 15. Metabolism of W. K. during grade walking in experiments without food. (Values per minute.) Continued. Date. Grade Dis- tance. Aver- age respi- ration- rate. Aver- age pul- monary venti- lation (re- duced). Aver- age pulse- rate. No. of steps. Car- bon di- oxide. Oxy- gen. Res- pira- tory quo- tient. Heat (com- puted). 1915. Apr. 22 p. ct. meters 70.7 27.9 liters. 21.9 111.8 c. c. 980 c. c. 1,319 0.75 cals. 6.25 70.9 28.7 21.6 108 111.8 963 1,224 .79 5.86 72.2 29.4 22.2 117 112.8 987 1,243 .80 5.97 72.0 29.8 21.7 111 111.8 997 1,311 .76 6.23 71.3 29.2 21.8 110 111.2 941 1,258 75 5 96 71.7 29.4 21.4 113 111.8 961 1,251 .77 5.96 Average . . 10.5 71.5 29.1 21.8 112 111.9 972 1,268 .77 6.04 Apr 23 70.7 27.7 22.7 110.6 975 1,207 81 5.81 71.2 27.9 22.8 111 111.0 945 1,183 .80 5.68 71.4 28.0 22.4 119 111.0 938 1,207 .78 5.76 71.3 28.2 21.6 120 110.0 911 1,281 .71 6.01 71.8 28.1 22.1 120 110.8 932 1,265 .74 5.98 Average . . 10.5 71.3 28.0 22.3 118 110.7 940 1,229 .76 5.84 Apr. 26 74.9 28.5 24.4 128 116.4 1,055 1,239 .85 6.03 75.5 28 8 24.4 133 116.4 1,043 1,232 85 5 99 75.9 29.0 24.5 142 116.0 1,036 1,250 .83 6.05 76.3 28.3 22.0 115.6 1,008 1,285 .79 6 15 76.6 29 5 23.0 116.2 1,017 1,276 .80 6 13 77.5 30.3 23.1 117.2 1,064 1,259 .85 6.11 Average . . 10.5 76.1 29.1 23.6 134 116.3 1,037 1,257 .82 6.07 Apr. 27 76.2 28.8 23.2 118 117.2 1,066 1,276 .84 6.19 76.9 28.7 23.1 122 115.8 1,054 1,288 .82 6.21 77.1 29.2 22.8 128 115.8 1,062 1,314 .81 6.32 76.9 29.2 23.0 130 115.6 1,088 1,206 .91 5.95 77.4 30.1 22.7 131 116.0 1,050 1,386 .76 6.59 77.8 31.0 23.1 131 116.8 1,070 1,280 .84 6.21 Average . . 10.5 77.1 29.5 23.0 127 116.2 1,065 1,292 .82 6.23 Apr. 28 75.6 28.2 21.8 117 114.4 1,039 1,417 .74 6.70 76.1 28.3 22.2 117 114.2 1,039 1,317 .79 6.31 76.7 28.5 22.3 121 115.2 1,044 1,242 .84 6.02 77.1 29.8 22.7 127 115.4 1,054 1,254 .84 6.08 Average . . 10.5 76.4 28.7 22.2 121 114.8 1,044 1,308 .80 6.28 Apr. 29 75.1 28.0 23.5 115 113.0 1,043 1,249 .84 6.06 75.8 28.3 24.1 119 113.8 1,044 1,202 .87 5.87 76 28 4 24.4 114.4 1,051 1,212 .87 5.92 76.8 28.7 23.8 127 115.2 1,068 1,215 .88 5.95 77.1 28.5 23.7 128 115.8 1,048 1,265 .83 6.12 76.9 28.8 24.0 115.6 1,057 1,311 .81 6.31 Average . . 10.5 76.3 28.5 23.9 122 114.6 1,052 1,242 .85 6.04 74 METABOLISM DURING WALKING. TABLE 15. Metabolism of W. K. during grade walking in experiments without food. ues per minute.) Continued. (Val- Date. Grade. Dis- tance. Aver- age respi- ration- rate. Aver- age pul- monary venti- lation (re- duced). Aver- age pulse- rate. No. of steps. Car- bon di- oxide. Oxy- gen. Res- pira- tory quo- tient. Heat (com- puted) . 1915. Apr 30 p. ct. meters. 77.7 28.2 liters. 23.6 117.4 c. c. 1,047 c. c. 1,253 0.84 cols. 6.08 78.8 29.2 24.1 119 119.0 1,075 1,297 .83 6.27 79.9 29.0 24.4 124 119.8 1,118 1,335 .84 6.47 80.2 29.2 24.3 124 119.6 1,105 (1,516) (.73) '6.50 80.9 29.1 24.1 125 119.8 1,090 1,387 .79 6.64 81.3 29.5 24.4 130 120.6 1,106 1,418 .78 6.77 Average . . 10.5 79.8 29.0 24.2 124 119.4 1,090 1,338 .81 6.44 77.0 28.2 22.3 117.2 1,083 1,277 .85 6.21 78.1 27.4 21.7 117.2 1,078 1,363 .79 6.53 78.4 27.5 21.4 118.0 1,080 1,272 .85 6.19 78.6 26.8 22.0 117.6 1,104 1,267 .87 6.19 79 1 27.6 21.3 119.2 1,094 1,463 .75 6 93 79.3 27.7 21.6 119.0 1,115 1,321 .85 6.42 10 5 78 4 27 5 21.7 118 1,092 1,327 .82 6 40 May 5 77.2 27.5 21.7 113 116.6 1,097 1,224 .90 6.03 77.8 28.2 23.8 117 117.2 1,083 1,406 .77 6.70 78.3 28.1 22.1 119 117.6 1,090 1,268 .86 6.18 78.6 28.2 22.5 120 118.2 1,125 1,282 .88 6.28 79.5 28.7 22.4 125 119.0 1,104 1,301 .85 6.33 80.1 28.9 23.1 133 119.0 1,163 1,348 .87 6.57 Average . . 10.5 78.6 28.3 22.6 121 117.9 1,110 1,305 .85 6.35 May 10 53.6 23.7 21.1 94.8 IjOll 1,159 .87 5.66 54 24 2 21.4 99 8 975 1,174 .83 5 68 55.0 24.5 20.9 98.6 1,045 1,244 .84 6.03 55.7 24.8 20.9 100.2 1,046 1,269 .83 6.12 56.0 26.1 21.5 103.0 974 1,282 .76 6.09 15 54 9 24 7 21.1 99 3 1 010 1,226 .82 5 92 May 11 57.5 24.1 19.8 96.6 935 1,170 .80 5.62 56.6 24.7 19.9 98.2 885 1,062 .84 5.14 56 6 24.6 19.4 99.8 896 1,050 .86 5 11 57.9 24.9 19.9 100.6 948 1,073 .89 5.27 58.1 24.8 19.0 100.4 908 1,176 .77 5.60 58.0 25.7 19.8 102.6 913 1,141 .80 5.48 13 57 5 24 8 19.6 99.7 914 1,112 82 5 37 May 12 58.3 25.7 21.0 103.4 928 1,170 .80 5.62 58.4 25.9 21.0 105.6 901 1,099 .82 5.30 58.6 26.0 21.6 105.2 988 1,119 .88 5.48 59 26 1 20.2 106.2 945 1,109 .85 5.39 58 9 26 3 20.0 106.0 893 1,143 78 5 46 59 1 26 8 20 105 4 907 1 134 80 5.44 13.0 58.7 26 1 20 6 105.3 927 1,129 82 5 45 1 Computed from the carbon dioxide of the period and the average of the respiratory quotient* for the day. STATISTICS OF EXPERIMENTS. 75 TABLE 15. Metabolism of W. K. during grade walking in experiments without food. (Val- ues per minute.) Continued. Date. Grade. Dis- tance. Aver- age respi- ration- rate. Aver- age pul- monary venti- lation (re- duced). Aver- age pulse- rate No. of steps. Car- bon di- oxide. Oxy- gen. Res- pira- tory quo- tient. Heat (com- puted). 1915. May 13 p.ct. meters. 60.4 26.9 liters. 25.1 119 106.0 c. c. 1,127 c. c. 1,356 0.83 cats. 6.56 60.2 28.4 25.3 125 107.4 1,110 1,401 .79 6.71 59.8 29.0 25.1 128 107.8 1,116 1,430 .78 6.83 59.9 29.3 23.6 105.6 1,142 1,382 .83 6 69 59 5 29.0 23 107.2 1,103 1,294 .86 6 31 59 2 28.6 22 5 105.0 1,081 1,309 .83 6 33 Average . . 15.0 59.8 28.5 24.1 124 106.5 1,113 1,362 .82 6.57 May 14 56.8 26.2 25.0 111 104.8 1,089 1,219 .89 5.99 54.9 27.1 24.1 112 104.8 1,042 1,199 .87 5.86 54.8 27.7 24.2 120 103.8 1,032 1,193 .87 5.83 55.3 27.7 22.3 117 102.2 1,047 1,182 .89 5.81 55.2 27.4 21.7 116 104.4 1,024 1 5.70 Average . . 15.3 55.4 27.2 23.5 115 104.0 1,047 1,198 .87 5.85 May 17 57.7 27.2 23.5 120 110.4 1,115 1,302 .86 6.35 58.2 27.9 23.5 126 111.2 1,103 1,295 .85 6.30 57.6 28.3 23.0 128 111.2 1,098 1,291 .85 6.28 57.6 28.0 22.4 129 109.2 1,075 1,289 .84 6 25 57.6 28.3 23.1 132 111.0 1,074 1,312 .82 6 33 Average . . 15.3 57.7 27.9 23.1 127 110.6 1,093 1,298 .84 6.30 May 18 60.3 27.5 26.4 115 109.8 1,169 1,301 .90 6.41 60.2 27.6 26.2 112 109.8 1,156 1,318 .88 6 46 60.1 27.9 26.4 118 111.8 1,157 1,326 .87 6.48 59.6 27.3 25.4 117 105.0 1,142 1,299 .88 6.37 59.3 27.6 24.7 117 104.8 1,107 1,288 .86 6 28 58.7 27.3 24.7 120 107.8 1,099 1,301 .85 6 33 Average . . 15.4 59.7 27.5 25.6 117 108.2 1,138 1,306 .87 6.38 May 24 65.5 28.2 26.5 129 115.8 1,286 1,468 .88 7 19 65.6 28.0 25.9 133 114.8 1,279 1,492 .86 7 27 65.7 28.7 26.8 136 117.0 1,292 1,419 .91 7 00 66.0 28.3 25.8 137 114.0 1,292 1,436 .90 7 07 66.3 28.4 148 114.6 1,261 ^.ge 66.6 29.1 25.7 151 115.2 1,289 1,468 .88 7 19 Average . . 15.3 66.0 28.5 26.1 139 115.2 1,283 1,457 .88 7.14 May 25 66.4 29.2 29.3 130 116.6 1,322 1,456 .91 7 19 67.4 29.0 29 4 134 116.4 1,300 1,502 87 7 34 66.9 28.7 29.1 135 115.6 1,304 1,480 .88 7 25 66.8 28.5 26.4 134 112.6 1,305 1,473 .89 7 24 66.6 28.5 25.3 138 110.8 1,258 1,471 .86 7 17 66.5 29.4 25.5 143 111.6 1,267 (1,668) ( 76) *7 05 Average . . 15.3 66.8 28.9 27.5 136 113.9 1,293 1,476 .88 7.23 'Computed from the carbon dioxide of the period and the average of the respiratory quotients for the day. 76 METABOLISM DURING WALKING. TABLE 15. Metabolism of W. K. during grade walking in experiments without food. (Val- ues per minute.) Continued. Date. Grade. Dis- tance. Aver- age respi- ration- rate. Aver- age pul- monary venti- lation (re- duced) Aver- age pulse- rate. No. of steps. Car- bon di- oxide. Oxy- gen. Res- pira- tory quo- tient. Heat (com- puted) . 1915. May 26 p. ct. meters. 77.6 30.0 liters. 31.0 134 121.3 c. c. 1,549 c. c. 1,656 0.94 cols. 8.24 78.9 31.0 32.3 143 122.8 1,553 1,853 .84 8.99 79.2 31.9 32.4 146 121.3 1,578 1,733 .91 8.55 79.7 31.1 30.9 143 120.0 1,577 1,917 .83 9.28 80.3 32.8 31.5 121.3 1,560 1,908 .82 9.21 80.7 32.9 32.2 121.5 1,573 1,795 .88 8.80 Average . . 15.3 79.4 31.6 31.7 142 121.4 1,565 1,810 .86 8.82 May 28 78.1 29.9 29.8 128 119.5 1,529 1,627 .94 8.09 78.9 30.2 29.1 136 119.0 1,478 1,648 .90 8.11 79.4 29.8 30.0 138 123.0 1,510 1,672 .91 8.25 79.8 28.7 28.7 137 119.8 1,517 1,687 .90 8.31 80.7 30.6 29.7 147 121.8 1,534 1,740 .88 8.53 80.9 31.4 30.2 152 122.0 1,552 1,771 88 8.68 Average . . 15.3 79.6 30.1 29.6 140 120.9 1,520 1,691 .90 8.33 May 29 79.0 29.4 32.1 135 119.0 1,516 1,676 .91 8.28 80.0 30.7 33.0 146 122.3 1,537 1,721 .90 8.48 80.4 32.1 34.3 149 122.5 1,583 1,752 .91 8.65 Average . . 15.3 79.8 30.7 33.1 143 121.3 1,545 1,716 .90 8.45 June 1 . ... 80.6 29:5 31.7 148 119.5 1,570 1,698 .93 8.42 80.2 31.7 32.7 155 121.2 1,601 1,735 .93 8.61 80.6 32.9 33.5 160 122.8 1-, 614 1,757 .92 8.69 Average . . 15.3 80.5 31.4 32.6 154 121.2 1,595 1,730 .92 8.56 J une 2 79.1 29.9 31.6 140 120.5 1,572 1,697 .93 8.42 79.8 31.4 32.7 147 122.0 1,579 1,711 .92 8.49 80.4 33.0 33.6 151 123.5 1,626 1,757 .93 8.71 Average . . 15.3 79.8 31.4 32.6 146 122.0 1,592 1,722 .92 8.52 June 7 49.9 25.6 25 1 100.8 1,228 1,381 '.89 6.78 50.1 26.4 24.9 102.6 1,237 1,410 .88 6.91 48.8 26.6 25.9 129 102.4 1,200 1,372 .88 6.72 47.9 27.6 23.4 126 98.0 1,175 1,324 .89 6.50 47.8 27.4 24.1 102.4 1,150 1,353 .85 6.58 47.3 29.0 24.9 139 104.2 1,179 1,369 .86 6.67 Average . . 20.0 48.6 27.1 24.7 131 101.7 1,195 1,368 .87 6.69 June 8. ... 46.7 26.6 25.0 97 4 1 127 1,308 .86 6.38 45.1 32.1 25 6 97 4 1 095 1,286 .85 6.25 43.9 29 1 24 6 95 2 1 070 1,257 .85 6.11 50.5 31.7 27 7 134 102 4 1 208 1 423 .85 6.92 50.4 50.0 29.8 31.3 28.0 28.6 141 146 104.2 106.0 1,242 1,253 1,451 1,464 .86 .86 7.07 7.14 Average . . 20.0 47.8 30.1 26.6 140 100.4 1,166 1,365 .85 6.64 STATISTICS OF EXPERIMENTS. 77 TABLE 15. Metabolism of W. K. during grade walking in experiments without food. (Val- ues per minute.) Continued. Date. Grade Dis- tance. Aver- age respi- ration- rate. Aver- age pul- monary venti- lation (re- duced). Aver- age pulse- rate. No. of steps. Car- bon di- oxide. Oxy- gen. Res- pira- tory quo- tient. Heat (com- puted) . 1915. June 9 p. ct. meters. 57.3 28.6 liters. 29.6 110.6 c. c. 1,335 c. c. 1,540 87 cals. 7.53 56.9 29.2 29.7 108.8 1,306 1,526 86 7.44 56.9 30.9 30.3 111.8 1,325 1,577 84 7.65 58.0 30.9 28 141 112 8 1 308 1 642 80 7 88 57.0 31.9 28.0 145 113.4 1,305 1 602 82 7 73 57.0 32.7 29.2 149 114 4 1,338 1,583 85 7 70 Average . . 20.0 57.2 30.7 29.1 145 112.0 1,320 1,578 .84 7.65 June 10 . . 63.4 31.8 34.6 116.6 1,497 1,703 88 8.34 63.0 33.0 35.3 117.6 1,491 1,726 87 8.43 62.9 33.5 36.2 154 118.4 1,488 1,719 .87 8.40 64.0 33.4 33.7 150 117 1,513 1,758 86 8.57 63.8 34.0 34.7 159 117.2 1,499 1,759 85 8.55 63.4 36.6 35 6 159 117 2 1,501 1,741 86 8 49 Average. . 20.0 63.4 33.7 35.0 156 117.3 1,498 1,734 .86 8.45 June 11 73.2 32.6 39.5 122.8 1,787 1,957 .92 9.68 73.4 35.8 45 9 123 1,793 1,978 91 9.76 74 35.2 41 5 158 124 1,795 1 993 90 9.81 69.0 35.0 40.0 162 121.5 1,614 1,869 .87 9.13 68.3 36.3 42.0 167 122.8 1,655 1,860 .89 9.14 Average . . 20.0 71.6 35.0 41.8 162 122.8 1,729 1,931 .90 9.51 June 12 73.5 31.8 39.9 153 120.3 1,749 1,929 .91 9.52 74.6 36.2 42.9 121.5 1,765 2,014 .88 9.87 74 A 38.4 44.2 162 121.0 1,748 2,004 .87 9.79 74.0 34.8 41 .0 120 5 1,737 1,948 89 9.57 74.0 36.1 42 163 123 1,704 1,974 86 9 62 74.0 37.7 43.2 164 122.5 1,725 1,992 .87 9.73 Average . . 20.0 74.1 35.8 42.2 161 121.5 1,738 1,977 .88 9.69 June 14 78.8 39.4 45 3 158 123.0 1,869 2,010 .93 9.97 79.8 39 6 47 4 169 126 8 1,906 2,052 .93 10.18 80 41.1 49 8 174 126 8 1,950 2,085 94 10.37 Average . . 20.0 79.5 40.0 47.5 167 125.5 1,908 2,049 .93 10.16 June 15 57.2 30.6 37.1 114.0 1,646 1,827 .90 9.00 55.0 54.6 54.4 53.1 53.1 33.9 32.9 34.1 33.6 34.2 34.7 33.3 33.9 32.8 32.9 141 140 141 142 145 110.0 109.0 109.8 109.4 108.4 1,544 1,517 1,534 1,447 1,449 1,760 1,751 1,723 1,737 1,731 .88 .87 .89 .84 .84 8.62 8.56 8.46 8.42 8.40 Average . . 25.0 54.6 33.2 34.1 142 110.1 1,523 1,755 .87 8.58 78 METABOLISM DURING WALKING. TABLE 15. Metabolism of W. K. during grade walking in experiments without food. (Val- ues per minute.) Continued. Date. Grade. Dis- tance. Aver- age respi- ration- rate. Aver- age pul- monary venti- lation (re- duced). Aver- age pulse- rate. No. of steps. Car- bon di- oxide. Oxy- gen. Res- pira- tory quo- tient. Heat (com- puted) . 1915. June 16 p. ct. meters. 59.9 32.9 liters. 41.5 153 114.4 c. c. 1,688 c. c. 1,902 0.89 cats. 9.34 58.7 36.9 41.5 154 116.0 1,626 1,861 .88 9.12 57.4 36.4 41.0 155 114.6 1,587 1,837 .87 8.98 51.8 34.4 37.2 149 109.4 1,443 1,690 .86 8.24 50.9 33.1 35.0 150 107.6 1,359 1,657 .82 8.00 50.1 33.4 34.6 151 108.6 1,343 1,635 .82 7.89 Average . . 25.0 54.8 34.5 38.5 152 111.8 1,508 1,764 .85 8.58 June 17 67.6 36.5 48.9 165 122.0 1,968 2,118 .93 10.51 66.8 38.8 50.7 170 120.0 1,887 2,115 .89 10.39 66.4 38.3 50.5 164 117.8 1,921 2,077 .93 10.30 66.6 38.8 49.7 166 121.8 1,891 2,103 .90 10.36 Average . . 25.0 66.9 38.1 50.0 166 120.4 1,917 2,103 .91 10.38 June 23 70 5 37 2 52*5 170 123.0 2,084 2,045 1.02 1 10.32 72.4 42.7 60.0 181 123.0 2,220 2,142 1.04 10.81 Average. . 25.0 71.5 40.0 56.3 176 123.0 2,152 2,094 1.03 1 10.57 Respiratory quotient of 1.00 used in computing. TABLE 16. Metabolism of E. D. B. during grade walking in experiments without food. ues per minute.) (Val- Date. Grade. Dis- tance. Aver- age respi- ration- rate. Aver- age pul- monary venti- lation (re- duced). Aver- age pulse- rate. No. of steps. Car- bon di- oxide. Oxy- gen. Res- pira- tory quo- tient. Heat (com- puted) . 1915. Oct. 30 p.ct. meters. 39 8 18 6 liters. 13 2 75 8 c. c. 518 c. c. 589 88 cals. 2 89 38.4 18 9 12.6 74.6 483. 602 .80 2.89 37.9 18 8 12.8 75 485 593 .82 2.86 37.9 18 7 12.8 73 4 488 605 81 2.91 Average . . 5 38.5 18.8 12.9 74.7 494 597 .83 2.89 Nov. 1 49 4 19 9 14 6 83 2 581 650 89 3 19 48 8 19 5 14 3 82 8 580 644 90 3 17 48 6 20 3 14 7 82 4 573 658 87 3 22 47 8 19 9 14 5 82 2 570 671 85 3 26 Average . . 5 48.7 19.9 14.5 82.7 576 656 .88 3.21 STATISTICS OF EXPERIMENTS. 79 TABLE 16. Metabolism of E. D. B. during grade walking in experiments without food. (Val- ues per minute.) Continued. Date. Grade Dis- tance. Aver- age respi- ration- rate. Aver- age pul- monary venti- lation (re- duced) Aver- age pulse- rate. No. of steps. Car- bon di- oxide. Oxy- gen. Res- pira- tory quo- tient. Heat (com- puted). 1915. Nov. 2 ... p. ct. meters 41.0 19.6 liters. 13.3 79.8 c. c. 520 c. c. 614 0.85 rah. 2.99 40.5 20.1 13.1 88 78.6 507 614 .83 2.97 40 4 20 4 13.1 79 6 515 631 .81 3.04 41.7 19.8 13.0 79.8 513 622 .83 3.01 Average . . 5 40.9 20.0 13.1 88 79.5 514 620 .83 3.00 Nov. 3 . . 43.1 20.0 13.8 77.6 536 610 .88 2.99 42 3 20 1 13.2 74.6 507 617 .82 2.98 42.1 19.9 13.4 78.4 508 622 .82 3.00 41.5 20.3 13.1 77.8 503 626 .80 3.01 Average 5 42.3 20.1 13.4 77.1 514 619 .83 2.99 Nov. 4. 48.3 20.3 14.3 81.6 538 659 .82 3.18 48.5 20.0 14.1 79.0 535 652 .82 3.15 48.1 19.9 14.1 79.6 529 645 .82 3.11 47.7 19.8 14.0 79.4 534 658 .81 3.17 Average 5 48.2 20.0 14.1 79.9 534 654 .82 3.16 Nov. 5 . 44.0 20.1 13.7 77 79.2 517 612 .84 2.97 42.6 20.3 13.7 81 77.0 508 620 .82 2.99 41.3 19.2 12.6 84 75.2 506 618 .82 2.98 42.0 19.4 13.4 86 75.0 506 623 .81 3.00 Average . . 5 42.5 19.8 13.4 82 76.6 509 618 .82 2.98 Nov. 6 49.5 20.0 14.4 81 80.6 556 618 .90 3.04 49.1 21.1 15.0 83 80.2 574 638 .90 3.14 47.9 20.1 14.1 87 79.2 538 622 .87 3.04 47.9 19.6 13.8 89 79.8 532 611 .87 2.99 46.7 19.7 13.8 93 77.6 536 630 .85 3.06 Average . . 5 48.2 20.1 14.2 87 79.5 547 624 .88 3.06 Nov. 8 53.5 21.0 15.4 84.4 614 654 .94 3.25 52.3 20.8 15.2 83.0 582 655 .89 3.22 52.3 20.8 14.8 86.0 591 669 .88 3.28 51 8 20 14 8 82.2 572 664 .86 3.24 Average. . 5 52.5 20.7 15.1 83.9 590 661 .89 3.25 Nov. 9 55.6 21.1 15.0 85.0 583 686 .85 3.34 54.9 20.6 14.3 84.4 569 673 .85 3.27 54.6 21.2 14.9 84.8 571 698 .82 3.37 53.9 21.0 14.5 83.6 561 687 .82 3.31 Average . . 5 54.8 21.0 14.7 84.5 571 686 .83 3.32 80 METABOLISM DURING WALKING. TABLE 16. Metabolism of E. D. B. during grade walking in experiments without food. (Val- ues per minute.) Continued. Date. Grade. Dis- tance. Aver- age respi- ration- rate. Aver- age pul- monary venti- lation (re- duced). Aver- age pulse- rate. No. of steps. Car- bon di- oxide. Oxy- gen. Res- pira- tory quo- tient. Heat (com- puted). 1915. Nov. 10 p. ct. meters. 57.3 22.4 liters. 15.9 86 88.0 c. c. 587 c. c. 684 0.86 cals. 3.33 56 5 22 9 15 8 87 6 577 694 .83 3.36 54 22 5 14 9 86 546 669 82 3.23 53 7 22 1 14 5 95 85.0 538 654 .82 3.16 Average . . 5 55.4 22.5 15.3 91 86.7 562 675 .83 3.27 Nov. 11 67.1 22.9 17 2 96 96.0 666 765 .87 3.74 65 8 23 3 16 8 95 6 647 776 .83 3.75 65 9 22 8 17 1 94 6 661 784 84 3.80 65 3 23.0 17 3 105 93.8 672 800 .84 3.88 Average . . 5 66.0 23.0 17.1 101 95.0 662 781 .85 3.80 Nov. 12 65 6 23.4 17 2 94 95.2 665 758 .88 3.71 65 4 22 9 17 2 95 2 676 789 .86 3.85 65 7 23 4 16 9 94 6 654 782 84 3.79 64 8 22 8 16 9 103 94 6 656 782 .84 3.79 Average . . 5 65.4 23.1 17.1 99 94.9 663 778 .85 3.78 Nov. 13 74 24.5 19 3 99 100.2 761 849 .90 4.18 74 1 23 8 19 99 4 753 891 84 4.32 74 24.1 18 7 99 6 733 882 .83 4.27 74 2 24 8 18 3 104 100 2 697 860 .81 4.14 Average . . 5 74.1 24.3 18.8 102 99.9 736 871 .85 4.24 Nov. 15 74 8 23 7 18 7 99 100 2 795 843 .94 4.19 75 24 9 19 4 101 4 785 865 91 4.27 75 24 7 18 7 106 101 2 775 874 .89 4.29 75 1 25 3 18 5 108 101 4 772 873 .89 4.29 Average . . 5 75.0 24.7 18.8 104 101.1 782 864 .91 4.26 Nov. 16 70 1 23 2 18 3 96 99 2 693 823 .84 3.99 75 1 24 2 18 5 102 8 706 868 .81 4.18 75 3 24 3 18 2 102 8 703 871 .81 4.19 74 7 24 7 18 1 105 100 6 702 870 .81 4.19 Average . . 5 73.8 24.1 18.3 101 101.4 701 858 .82 4.14 Nov. 17 48 7 23 9 19 5 99 81 6 746 870 .86 4.24 48 5 24 4 19 5 81 4 736 889 .83 4.30 47 6 23 7 18 7 81 2 738 882 .84 4.28 47 3 25 1 19 5 110 80 2 740 890 .83 4.31 Average . . 10.3 48.0 24.3 19.3 105 81.1 740 883 .84 4.28 Nov. 22 42 5 20 2 17 77 8 693 786 88 3.85 41 5 20 9 16 7 78 670 794 .84 3.85 41 5 21 4 16 9 77 4 665 817 .81 3.93 41 5 22 2 17 2 77 6 673 825 .82 3.98 Average. . 10.3 41.8 21.2 17.0 77.7 675 806 .84 3.91 STATISTICS OF EXPERIMENTS. 81 TABLE 16. Metabolism of E. D. B. during grade walking in experiments without food. (Val- ues per minute.) Continued. Date. Grade Dis- tance. Aver- age respi- ratioD rate. Aver- age pul- monary venti- lation (re- duced) Aver- age pulse- rate. No. of steps. Car- bon di- oxide. Oxy- gen. Res- pira- tory quo- tient. Heat (com- puted). 1915. Nov. 23 p.ct. meters 57.8 23.5 liters. 21.9 102 87.6 c. c. 834 c. c. 971 0.86 cals. 4.73 57.0 24.2 22.2 87.4 886 991 .89 4.87 57.1 24.5 21.6 114 87 4 839 1,001 .84 4.85 56.8 23.4 21.1 117 86.2 857 1,007 .85 4.90 Average . . 10.0 57.2 23.9 21.7 111 87.2 854 993 .86 4.84 Nov. 24 56.5 22.2 20.7 100 85.4 835 966 .86 4.71 57.4 23.0 20.9 86.0 852 1,011 .84 4.90 58.3 23.4 21.7 87.2 873 1,031 .85 5.01 57.4 22.4 20.2 116 86.2 839 1,021 .82 4.93 Average . . 10.0 57.4 22.8 20.9 108 86.2 850 1,007 .84 4.88 Nov. 26 66.1 21.8 21.0 92.6 1,027 1,100 .93 5.46 66.6 23.1 21.3 94.2 1,041 1,118 .93 5.55 66.8 22.9 21.3 97.2 1,043 1,149 .91 5.67 66.6 23.4 21.2 93.2 1,048 1,155 .91 5.70 Average . . 10.0 66.5 22.8 21.2 94.3 1,040 1,131 .92 5.60 Nov. 27 66.1 22.6 22.4 94.6 (936) 1,093 1 ( . 87) 5.34 65.7 24.0 22.6 91.6 1,006 1,112 .90 5.48 66.0 23.7 21.9 95.6 991 1,128 .88 5.53 65.8 23.6 21.8 95.8 983 1,147 .86 5.59 65.9 24.7 21.9 97.4 980 1,159 .85 5.64 Average . . 10.0 65.9 23.7 22.1 95.0 990 1,128 .88 5.53 Nov. 29 65.6 24.1 23.5 110 97.6 993 1,100 .90 5.42 65.4 24.3 23.4 96.6 985 1,135 .87 5.55 65.8 24.3 22.7 95.4 988 1,167 .85 5.68 65.6 24.1 27.1 132 96.2 962 1,180 .82 5.69 Average . . 10.0 65.6 24.3 24.2 121 96.5 982 1,146 .86 5.59 Nov. 30 77.6 24.5 26 9 113 100.6 1,189 1,345 .88 6.59 78.4 26.4 27.2 101.8 1,183 1,373 .86 6.69 78.8 25.9 27.9 102.0 1,183 1,378 .86 6.72 79.0 26.7 28.1 136 102.2 1,207 1,402 .86 6.83 Average . . 10.0 78.5 25.9 27.5 125 101.7 1,191 1,375 .87 6.72 Dec. 1 79.3 24 9 27 2 120 103.8 1,200 1,284 .93 6.37 80.1 80.6 80.0 26.6 26.9 25.9 28.7 28.8 28.8 104.4 104.2 105.0 1,209 1,201 1,194 1,341 1,362 1,397 .90 .88 .85 6.60 6.67 6.79 Average . . 10.0 80.0 26.1 28.4 120 104.4 1,201 1,346 .89 6.61 Assumed. 82 METABOLISM DURING WALKING. TABLE 16. Metabolism ofE.D.B. during grade walking in experiments without food. ( Val- ues per minute.} Continued. Date. Grade. Dis- tance. Aver- age respi- ration- rate. Aver- age pul- monery venti- lation (re- duced). Aver- age pulse- rate. No. of steps. Car- bon di- oxide. Oxy- gen. Res- pira- tory quo- tient. Heat (com- puted). 1915. Dec. 2 p. ct. meters. 68.7 25.1 liters. 25.0 108 97.4 c. c. 1,063 c. c. 1,117 .95 cals. 5.57 68.7 24.7 25.2 117 97.8 1,054 1,151 .92 5.70 68.1 24.7 24.0 122 96.8 1,038 1,161 .89 5.70 67.6 23.4 23.4 124 97.4 1,018 1,162 .88 5.69 Average. . 10.0 68.3 24.5 24.4 118 97.4 1,043 1,148 .91 5.67 Dec. 3 70.7 24.7 24.2 112 97.0 1,089 1,189 .92 5.88 70.8 26.5 26.3 116 97.8 1,084 1,205 .90 5.93 70.2 25.0 25.5 120 96.8 1,059 1,218 .87 5.95 70.4 25.3 24.4 124 98.4 1,065 1,236 .86 5.03 Average . . 10.0 70.5 25.4 25.1 118 97.5 1,074 1,212 .89 5.95 Dec. 4 44.8 23.6 22.2 . 78.8 936 1,020 .92 5.05 44.7 23.8 22.1 78.4 916 1,036 .88 5.08 44.2 24.5 21.9 78.8 894 1,039 .86 5.07 44.0 23.2 21.3 78.0 881 1,042 .85 5.07 Average . . 15.0 44.4 23.8 21.9 78.5 907 1,034 .88 5.07 Dec. 6 41.5 22.6 21.0 101 77.0 866 950 .91 4.69 39.1 22.7 20.6 107 76.4 834 930 .90 4.58 38.3 24.0 20 7 108 74.8 819 910 .90 4.48 37.1 23.0 20 3 110 75.6 805 903 .89 4.44 Average . . 15.0 39.0 23.1 20.7 107 76.0* - 831 923 .90 4.54 Dec. 7 48.0 24 7 23 7 110 83 976 1,076 .91 5.31 46.9 26.3 23.6 118 81.6 945 1,060 .89 5.21 44.4 25.6 22 5 117 79.2 894 1,020 .88 5.00 Average. . 15.0 46.4 25.5 23.3 115 81.3 938 1,052 .89 5.17 Dec. 8 57.5 25 1 26 1 122 1,099 1,247 .88 6.11 58.6 27.2 27.0 131 1,102 1,314 .84 6.37 58.5 27.4 32.4 134 89.2 1,096 1,326 .83 6.42 57.9 26.4 26.0 133 89.0 1,088 1,285 .85 6.25 58.4 26.4 26 89.0 1,072 1,340 .80 6.43 59.1 27.5 27 3 90.4 1,100 1,371 .80 6.58 Average . . 15.0 58.3 26.7 27.5 130 89.4 1,093 1,314 .83 6.36 Dec. 13 67 3 25 5 28 8 123 98 1 233 1 396 88 6 84 67 2 26 29 4 131 98 1 234 1,443 .86 7.03 66 26 1 29 2 138 96 9 1 200 1,419 .85 6.90 Average . . 15.0 66.8 25.9 29.1 131 97.6 1,222 1,419 .86 6.92 STATISTICS OF EXPERIMENTS. 83 TABLE 16. Metabolism of E. D. B. during grade walking in experiments without food. (Val- ues per minute.) Continued. Date. Grade. Dis- tance. Aver- age respi- ration- rate. Aver- age pul- monary venti- lation (re- duced). Aver- age pulse - rate. No. of steps. Car- bon di- oxide. Oxy- gen. Res- pira- tory quo- tient. Heat (com- puted) . 1915. Dec. 14 p. ct. meters. 73 8 24 3 liters. 31 2 113 104 4 c. c. 1,389 c. c. 1 544 90 cals. 7 60 74 27 2 31 2 127 103 2 1,368 1 571 87 7.68 73 5 27 4 32 7 129 100 8 1,332 1 553 86 7 57 72.8 27 9 32 7 129 101.5 1,331 1,535 87 7.50 73 1 27 1 30 2 140 102.0 1,322 1,616 82 7.80 Average . . 15.0 73.4 26.8 31.6 128 102.4 1,348 1,564 .86 7.62 Dec. 15 75.0 22.9 28.8 113 105.6 1,376 1,575 .87 7.70 75.1 25.8 30.3 120 104.8 1,341 1,602 .84 7.77 74 9 26.1 30 125 105.0 1,326 1,592 83 7.70 74 8 24 5 29 8 126 103.2 1,344 1,560 86 7.60 75 3 26 5 29 5 132 104.2 1,312 1 621 81 7.80 76.0 26.9 31.3 136 105.6 1,335 1,655 .81 7.97 Average. . 15.0 75.2 25.5 30.0 125 104.7 1,339 1,601 .84 7.76 Dec. 16 80.3 25.4 33.6 124 107.0 1,497 1,671 .90 8.23 81.0 26.4 34.2 130 107.0 1,480 1,668 .89 8.19 81.4 26.4 33.9 107.2 1,501 1,738 .86 8.47 80 6 24.8 32.0 134 107.0 1 , 460 . 1,649 89 8.10 82 2 27 6 33 5 139 107 8 1,472 1,767 83 8 55 82 27 3 33 8 144 106 8 1,476 1 780 83 8 61 Average . . 15.0 81.3 26.3 33.5 134 107.1 1,481 1,712 .87 8.37 Dec. 17 54.7 24.4 27.8 113 90.8 1,204 1,354 .89 6.65 54.4 24.4 27.6 119 89.2 1,171 1,386 .85 6.74 52.0 24 25.8 118 88.0 1,110 1,334 .83 6.45 53 4 25 2 26.6 123 89.4 1,130 1,378 .82 6.65 53 6 23 2 26 126 88 7 1,130 1,374 82 6.63 52.2 24.9 26.6 128 86.2 1,130 1,384 .82 6.68 Average . . 20.0 53.4 24.4 26.7 121 88.7 1,146 1,368 .84 6.63 Dec. 18 39 7 22.2 21 9 77.2 952 1,067 .89 5.24 37 8 22 9 21 2 76.8 864 1,042 .83 5.04 37 6 24 6 21 5 78.2 870 1,044 83 5.05 45.8 23.2 24.0 110 82.6 1,037 1,167 .89 5.73 45.3 23.3 23.1 110 82.6 982 1,190 .83 5.76 44.4 23.8 22.9 108 82.4 970 1,170 .83 5.66 Average . . 20.0 41.8 23.3 22.4 109 80.0 946 1,113 .85 5.41 Dec. 20 . . 65 6 24 9 33 4 119 100 2 1,523 1,614 94 8 03 65.8 24.9 33.4 127 99.6 1,499 1,634 .92 8.09 66.0 26.1 34.6 131 100.2 1,491 1,641 .91 8.10 66.4 24.9 34.4 100.6 1,521 1,626 .94 8.09 67.5 25.7 34.8 102.6 1,521 1,735 .88 8.50 67.1 25.4 34.1 101.0 1,514 1,748 .87 8.54 Average . . 20.0 66.4 25.3 34.1 126 100.7 1,512 1,666 .91 8.22 84 METABOLISM DURING WALKING. TABLE 16. Metabolism of E. D. B. during grade walking in experiments without food. (Val- ues per minute.) Continued. Date. Grade Dis- tance Aver- age respi- ration rate. Aver- age pul- monary venti- lation (re- duced) Aver- age pulse- rate. No. of steps. Car- bon di- oxide. Oxy- gen. Res- pira- tory quo- tient. Heat (com- puted). 1915. Dec. 21 p. ct. meters 69 4 25 5 liters. 35 4 103 c. c. 1 602 c. c. 1 706 94 cals. 8.48 70.5 26.1 35 7 106 4 1,602 1,808 .89 8.88 70.9 26.4 39 8 105 4 1,584 1,839 .86 8.97 Average . 20.0 70.3 26.0 37.0 104.9 1,596 1,784 .90 8.78 Deo. 22 69 4 24 6 33 4 104 4 1 544 1,715 90 8.44 69 5 26 6 34 4 104 8 1 550 1,746 89 8.58 71 2 25 8 34 7 106 6 1 569 1 784 88 8.74 Average . . 20.0 70.0 25.7 34.2 105 3 1,554 1,748 .89 8.59 Dec. 31 79 6 24 9 41 6 109 8 2 025 2,217 91 10.94 80.6 30.3 46 1 110 6 2,058 2,322 .89 11.41 Average . . 20.0 80.1 27.6 43.9 110 2 2,042 2,270 .90 11.18 1916. Jan. 1 79 3 26 9 41 3 110 1 949 2,162 90 10.65 80 1 27 7 43 8 112 6 2 001 2 281 88 11.18 81 6 28 1 47 112 6 2 080 2 373 88 11.63 Average . . 20.0 80.3 27.6 44.0 111.7 2,010 2,272 .88 11.13 Jan. 3 43.1 23 4 27 5 85 6 1 184 1 453 82 7.01 42.5 24.1 31 8 84 1,181 1,456 .81 7.01 42 3 24 28 85 1 183 1 444 82 6 97 Average . . 25.0 42.6 23.8 29.1 84.9 1,183 1,451 .82 7.00 Jan. 4 59 2 24 6 37 97 2 1 730 1,909 .91 9.42 60 5 24 8 37 5 96 1 705 1 954 87 9.55 60.4 25 7 38 7 94 6 1,729 1,998 .87 9.76 60.1 29 1 48 8 96 2 1,728 1,999 .86 9.75 Average. . 25.0 60.1 26.1 40.5 96.0 1,723 1,965 .88 9.63 Jan. 5 69 5 27 2 45 5 105 6 2 037 2 281 89 11.20 69.1 28.1 50 7 103 4 2,070 2,223 .93 11.03 Average . . 25.0 69.3 27.7 48.1 104.5 2,054 2,252 .91 11.12 Feb. 2 45 3 22 1 30 8 132 86 1 385 1 558 89 7 65 46.6 22 1 33 144 84 4 1 500 1,667 .90 8.21 47.5 23.7 36.0 159 87.2 1,574 1,778 .89 8.73 Average . . 25.0 46.5 22.6 33.3 145 85.9 1,486 1,668 .89 8.19 Feb. 3 51 6 22 4 32 9 140 91 4 1 556 1 730 90 8.52 53.6 52.7 26.9 25.0 37.2 35.7 149 156 93.2 91.4 1,610 1,560 1,863 1,822 .86 .86 9.08 8.88 Average . . 25.0 52.6 24.8 35.3 148 92.0 1,575 1,805 .87 8.82 STATISTICS OF EXPERIMENTS. 85 TABLE 16. Metabolism of E. D. B. during grade walking in experiments without food. (Val- ues per minute.) Continued. Date. Grade. Dis- tance. Aver- age respi- ration rate. Aver- age pul- monary venti- lation (re- duced). Aver- age pulse- rate. No. of steps. Car- bon di- oxide. Oxy- gen. Res- pira- tory quo- tient. Heat (com- puted). 1916. Feb. 4 p. ct. meters. 60.8 24.1 liters. 39.0 147 100.5 c. c. 1,801 c. c. 1,954 0.92 cals. 9.67 62.7 27.6 45.3 162 100.0 1,932 2,141 .90 10.54 63.2 29 2 50.6 96.2 1,976 2,158 .92 10.68 Average . . 25.0 62.2 27.0 45.0 155 98.9 1,903 2.084 .91 10.29 Feb 5 68.0 26.6 44.2 105.4 1,963 2,189 .90 10.78 72.1 26.2 52.7 169 103.0 2,184 2,385 .92 11.80 73.0 27.4 50.3 170 105.8 2,153 2,391 .90 11.77 Average . . 25.0 71.0 26.7 49.1 170. 104.7 2,100 2,322 .90 11.43 Feb 7 74.7 26.5 56.2 111.8 2,370 2,506 .95 12.49 76.5 28.1 59.1 176 107.5 2,436 2,592 .94 12.89 76.4 27.1 57.9 175 108.6 2,373 2,489 .95 12.41 Average . . 25.0 75.9 27.2 57.7 176 109.3 2,393 2,529 .95 12.61 Feb. 8 49.3 23.8 36.1 129 94.0 1,626 1,811 .90 8.92 49.6 27.7 38.2 135 94.4 1,637 1,876 .87 9.17 42.5 26.6 32.8 132 81.6 1,373 1,644 .83 7.95 42.4 26.6 33.6 136 85.0 1,417 1,649 .86 8.04 Average . . 30.0 46.0 26.2 35.2 133 88.8 1,513 1,745 .87 8.53 Feb. 9 48.8 26.0 36.7 134 97.4 1,646 1,838 .90 9.05 50.2 29.2 40.0 142 98.2 1,743 1,967 .89 9.66 57.3 27.2 44.2 159 100.0 1,966 2,203 .89 10.82 57.9 27.4 44.8 163 96.0 1,964 2,198 .89 10.80 Average . . 30.0 53.6 27.5 41.4 150 97.9 1,830 2,052 .89 10.08 Feb. 10 60.5 28.9 48.6 152 102.2 2,062 2,197 .94 10.93 62.6 28.0 52.9 167 104.8 2,211 2,344 .94 11.66 Average . . 30.0 61.6 28.5 50.8 160 103.5 2,137 2,271 .94 11.29 Feb. 11 69.4 28.5 58.6 171 106.5 2,485 2,615 .95 13.04 69.1 27.6 58.4 174 108.8 2,462 2,597 .95 12.95 69.9 27.5 57.2 175 113.2 2,461 2.629 .94 13.07 Average . . 30.0 69.5 27.9 58.1 173 109.5 2,469 2,614 .94 13.00 Feb. 12 68.3 27.6 53.7 152 120.3 2,312 2,455 .94 12.21 74.6 29.1 65.5 173 116.3 2,629 2,770 .95 13.81 Average . . 30.0 71.5 28.4 59.6 163 118.3 2,471 2,613 .95 13.03 Feb. 14 67.8 27.2 52.2 159 110.8 2,269 2,452 .93 12.16 68.8 28.4 56.8 172 108.0 2,353 2,510 .94 12.48 Average . . 30.0 68.3 27.8 54.5 166 109.4 2,311 2,481 .93 12.31 86 METABOLISM DURING WALKING. TABLE 16. Metabolism of E. D. B. during grade walking in experiments without food. (Val- ves per minute.) Continued. Date. Grade. Dis- tance. Aver- age respi- ration- rate. Aver- age pul- monary venti- lation (re- duced). Aver- age pulse- rate. No. of steps. Car- bon di- oxide. Oxy- gen. Res- pira- tory quo- tient. Heat (com- puted). 1916. Feb 15 p. ct. meters. 43.1 26.0 liters. 39.2 135 98.8 c. c. 1,687 c. c. 1,926 0.88 cals. 9.44 45.7 28.1 40.5 145 101.0 1,747 2,048 .85 9.96 46.2 29.1 41.7 155 88.3 1,761 2,047 .86 9.98 Average . . 35.0 45.0 27.7 40.5 145 96.0 1.732 2,007 .86 9.78 Feb 16 57.7 28.5 53.7 168 107.7 2,300 2,574 .89 12.64 58.5 31.1 56 8 176 106.3 2,315 2,524 .92 12.49 56.6 29.1 53 178 96.8 2,185 2,386 .92 11.81 Average . . 35.0 57.6 29.6 54.5 174 103.6 2,267 2,495 .91 12.32 Feb 17 . .. 62.3 28.1 61.5 174 104.8 2,534 2,723 .93 13.51 62.5 30.0 62 180 101.0 2,479 2,726 .91 13.46 Average . . 35.0 62.4 29.1 61.8 177 102.9 2,507 2,725 .92 13.48 Feb. 18 46.1 28.5 45.2 148 91.3 2,013 2,214 .91 10.93 50.6 29.4 60 9 161 91.0 2,178 2,375 92 11.75 51.8 30.5 59 3 174 87.3 2 356 2 505 .94 12.46 Average . . 40.0 49.5 29.5 51.8 161 89.9 2,182 2,365 .92 11.70 Feb. 19 53.7 29.5 57.3 156 102.6 2,385 2,573 .93 12.76 54.3 32.8 64 3 168 98.0 2 500 2,659 .94 13.22 54.0 31.3 63 7 169 100.0 2 468 2 562 96 12.80 Average . . 40.0 54.0 31.2 61.8 164 100.2 2,451 2,598 .94 12.92 Feb. 21 57.2 31.1 71.1 177 101.5 2,656 2,766 .96 13.82 57.2 31.1 71 5 177 103.3 2 667 2 771 96 13.85 57.0 32 3 73 3 179 98 5 2 671 2 728 98 13 70 Average . . 40.0 57.1 31.5 72.0 178 101.1 2,665 2,755 .97 13.80 Feb. 22 64.9 36.1 84.6 186 102.5 3,004 3,104 .97 15.55 65.4 33 8 84 4 186 104 3 3 030 3 159 96 15 79 Average.. 40.0 65.2 35.0 84.5 186 103.4 3,017 3,132 .96 15.65 Feb. 23 40.6 31.2 55 1 161 95 7 2,183 2 446 89 12 01 41 8 29 1 53 2 164 98 6 2 234 2 390 93 11 85 44 1 31 8 59 9 170 100 2 423 2 519 96 12 59 Average . . 45.0 42.2 30.7 56.1 165 98.1 2,280 2,452 .93 12.16 Feb. 24 . . 42 8 31 61 4 169 95 8 2 315 2 421 96 12 10 42 1 31 1 62 9 173 89 2 242 2322 Q7 UfiQ Average . . 45.0 42.5 31.1 62'2 171 92.4 2,279 2,372 .96 11.85 STATISTICS OF EXPERIMENTS. 87 TABLE 16. Metabolism of E. D. B. during grade walking in experiments without food. (Val- ues per minute.) Continued. Date. Grade. Dis- tance. Aver- age respi- ration- rate. Aver- age pul- monary venti- lation (re- duced). Aver- age pulse- rate. No. of steps. Car- bon di- oxide. Oxy- gen. Res- pira- tory quo- tient. Heat (com- puted) . 1916. Feb. 25 p. ct. meters. 60.7 27.2 liters. 45.6 139 103.2 c. c. 2,041 c. c. 2,247 0.91 cats. 11.09 60.9 30.2 49.6 144 103.2 2,123 2,314 .92 11.45 Average . . 30.0 60.8 28.7 47.6 142 103.2 2,082 2,281 .91 11.26 Feb. 26 68.6 28.4 50.9 148 103.2 2,307 2,509 .92 12.41 70.1 32.0 58.3 158 105.2 2,467 2,674 .92 13.23 Average . . 30.0 69.4 30.2 54.6 153 104.2 2,387 2,592 .92 12.83 Feb. 28 66.7 28,0 52.0 149 107.6 2,302 2,443 .94 12.15 67.1 32.4 57.9 150 107.2 2,446 2,573 .95 12.83 Average . . 30.0 66.9 30.2 55.0 150 107.4 2.374 2,508 .95 12.50 Feb. 29 68.4 31.2 54.1 147 105.2 2,232 2,441 .91 12.05 68.5 33.0 58.8 158 102.8 2,336 2,540 .92 12.57 Average . . 30.0 68.5 32.1 56.5 153 104.0 2,284 2,491 .92 12.33 Mar 4 49.1 27.6 42.2 131 1,621 1,764 .92 8.73 48.6 30.8 44.4 137 1,624 1,829 .89 8.98 47.2 29 8 42.9 137 1,552 1,751 .89 8.60 49 1 27.8 43 4 143 1,625 1,914 .85 9.31 30 48 5 29 43 2 137 1,606 1,815 .88 8 89 Mar 6 51.1 27.1 45.2 128 1,763 1,923 .92 9.52 52 2 29.7 48.0 138 1,783 2,013 .89 9.89 52.5 27 9 46.9 142 1,800 2,044 .88 10.02 53.0 30 48.1 150 1,795 2,015 .89 9.90 30 52 2 28 7 47 1 140 1,785 1,999 .89 9 82 Mar. 7... 51.0 28.2 44.2 132 1,774 1,909 .93 9.47 51.1 28.3 44.0 143 1,682 1,942 .87 9.49 30 51.1 28 3 44.1 138 1,728 1,926 .90 9.48 Mar. 8 51.2 28.1 46.7 139 1,761 1,891 .93 9.38 51.2 29.7 47.2 143 1,735 1,942 .89 9.54 51 3 29.8 49.9 150 1,807 1,961 .92 9.70 52 3 30 8 50.8 154 1,766 2,073 .85 10.08 51 5 28 7 48.5 152 1,769 2,011 .88 9.85 51.7 29.5 47.9 160 1,723 2,043 .84 9.91 Average 30 51 5 29.4 48.5 150 1,760 1,987 .89 9.76 Mar. 23 ... 62.5 23.5 22.3 101 937 1,127 .83 5.45 61 9 24 3 23.1 104 955 1,089 .88 5.34 10 62 2 23 9 22.7 103 946 1,108 .85 5.39 88 METABOLISM DURING WALKING. TABLE 16. Metabolism ofE. D. B. during grade walking in experiments without food. (Val- ues per minute.) Continued. Date. Grade. Dis- tance. Aver- age respi- ration- rate. Aver- age pul- monary venti- lation (re- duced). Aver age pulse- rate. No. of steps. Car- bon di- oxide. Oxy- gen. Res- pira- tory quo- tient. Heat (com- puted). 1916. Mar 24 p. ct. meters. 57.1 22.6 liters. 20.9 96 c. c. 862 c. c. 1,010 85 calf. 4 91 56.7 23.4 20.3 102 847 996 85 4 84 Average 8 9 56.9 23.0 20.6 99 855 1,003 85 4 88 Apr 6 46.3 21.7 20.8 99 770 908 85 4 42 47 4 21 2 19.1 101 784 904 87 4 42 47 3 21 3 18.7 104 773 907 85 4 41 10 47 21 4 19 5 101 776 906 86 4 42 Apr 7 45 6 21.7 19.2 90 757 906 83 4 38 46 5 21 3 19.5 99 767 909 84 4 41 47 2 21 5 19.2 102 773 911 85 4 43 10 46 4 21 5 19 3 97 766 909 84 4 41 Apr. 8 35 2 20 17.2 90 681 795 86 3 88 36 2 20 4 17.8 95 700 777 90 3 83 36 21 2 17.3 94 679 781 87 3 82 10 35 8 20 5 17.4 93 687 784 88 3 84 Apr 14 40 5 21 6 18.3 85 559 667 .84 3 23 40 8 21 6 18.3 88 552 645 86 3 14 39 8 22 18.2 536 624 86 3 04 Average 5 40 4 21.7 18.3 87 549 645 .85 3 14 Apr. 15 39 6 20.9 17.1 80 476 543 .88 2 66 40 1 21 7 16 9 84 458 530 86 2 58 39 5 21 9 16.9 90 453 518 .88 2 54 2 4 39 7 21 5 17.0 85 462 530 87 2 59 TABLE 16a. Average body-temperature and blood-pressure of E. D. B. during grade walking in experiments without food. (Values per minute.) Date. Average body- tempera- ture. Date. Average body- tempera- ture. Date. Average body- tempera- ture. 1916. C. 38 39 1916. Feb. 3 C. 37.54 1916. Feb. 5 C. 37.44 38.63 38.03 38 33 37.78 07 04. QC t;i 37 97 37 69 p_u o 07 1Q 37 53 Feb. 4 37.50 Feb. 7 37 61 37.75 38.31 QC 7Q 37.89 37 fiA V7 4Q Average 38.20 Average . . . 37 72 STATISTICS OF EXPERIMENTS. 89 TABLE 16a. Average body-temperature and blood-pressure of E. D. B. during grade walking in experiments without food. (Values per minute.) Continued. Date. Average body- tempera- ture. Date. Average body- tempera- ture. Date. Average body- tempera- ture. Blood- pres- sure. 1916. Feb. 8 C. 36.97 37.93 38.24 38.31 1916. Feb. 21 C. 37.72 38.05 38.20 1916. Mar. 7 Average .... Mar. 8 Average .... Mar 23 C. 37.55 37.91 mm. Average .... Feb. 9 Average .... Feb 22 37.75 37.99 37.86 37.57 38.26 37.67 38.24 37.90 38.39 38.29 37.77 38.37 38.76 38.89 Average .... Feb 23 Average. . . . Feb 11 38.29 38.11 38.33 38.33 38.45 Average .... Feb 24 38.01 38.00 38.25 37.97 37.53 37.62 119 116 Average .... Feb. 12 38.26 Average .... Mar 24 37.92 38.50 37.58 118 38.07 Average .... Feb. 25 37.74 37.86 126 127 37.37 38.13 38.21 Average .... Apr 6 Average .... Feb. 14 37.31 38.14 37.80 127 37.75 Average .... Feb 26 37.25 37.53 37.53 122 128 128 37.49 38.47 37.73 Average .... Apr. 7 Average .... Feb. 15 37.25 37.97 37.98 Average .... Feb. 28 37.44 126 37.65 38.47 38.74 37.61 36.66 37.17 37.15 129 130 131 Average .... Feb 16 Average .... Apr 8 37.11 Average .... Feb. 29 38.29 36.99 130 37.11 37.76 38.47 38.59 36.90 37.09 37.22 137 138 141 Average .... Feb. 17 36.98 37.89 Average .... Apr. 14 Average .... Mar. 4 38.27 37.44 37.07 139 37.68 38.48 37.23 37.70 36.70 36.68 37.06 37.41 37.30 128 128 129 Average .... Feb 18 Average. . . . Mar. 6 Average .... Apr 15 38.08 37.26 128 37.73 38.59 39.03 37.08 Average Feb 19 37.00 37.28 37.34 127 129 127 37.27 38.01 37.56 38.12 Average .... 38.45 37.21 128 36.95 37.97 38.33 Average .... 37.74 37.75 90 METABOLISM DURING WALKING. DISCUSSION OF RESULTS. The data given in the preceding section will be discussed in the gen- eral order of standing, horizontal-walking, and grade-walking experi- ments, considering first in each case the gaseous metabolism and the heat-output, then the physiological effects of the work performed. For such discussion reference will be made to tables in the statistical section (see p. 42) from which, with few exceptions, material for the other tables has been drawn. BASAL METABOLISM. While the special topic of this report is not basal metabolism, basal values were obtained for all of our subjects, usually by other members of the Laboratory staff, in experiments carried out for an entirely different purpose. Ordinarily these values were determined with a respiratory- valve apparatus or the universal respiration apparatus, and not infrequently with the clinical respiration apparatus. 1 Many observations were made in the comparison of the several methods, particularly during the development of the clinical respiration appa- ratus. The conditions in all of the experiments were those required for basal values, namely, the subject was in the lying position, in a post-absorptive condition, and with the greatest possible degree of muscular repose. The values may thus be considered to be true basal values. The data for all of the subjects except E. L. F. have already been reported in abstract in the biometrical analysis of basal metabol- ism measurements by Harris and Benedict. 2 The basal-metabolism measurements were not used in the present study, save for the purpose of comparing the metabolism of the sub- jects in the lying position with the values for their metabolism when they were standing, to determine the influence of the effort of standing. (See table 22, p. 101.) Since these measurements of the basal metab- olism were most carefully made, they should be recorded here, but the average results only are reported. (See table 17.) In considering the values in table 17, it is obvious that the only re- sults which contribute to the comparison of individuals with each other are those which have been computed on the basis of unit of body-weight or body-surface, for the individuals studied had materially different body-weights. The respiratory quotients are, for the most part, con- siderably above the quotient normally ascribed to the average man, viz, 0.82, but nevertheless are within a reasonable range. The respira- tory quotient of H. R. R. varied considerably in the individual experiments, ranging from 0.76 to 0.93. His average of 0.80 is lower than that for any other subject. Furthermore, it is clear that H. R. R. Benedict and Tompkins, Boston Med. and Surg. Journ., 1916, 174, pp. 857, 898, and 939. 'Harris and Benedict, Carnegie Inst. Wash. Pub. No. 279, 1919, pp. 42 and 43. Only such of the data for A. J. O. and H. M. S. as were obtained at about the period of this research are used for comparison in this report. (See table 17.) BASAL METABOLISM. 91 o 3 O X w b (9 CN CO (N O ^ H c tn co t- (N O> i l 0) i-l rH (N 00 5 o OQ * S CO o o> S- 2 t ^ 9 o ^ B l4l *< CO X t>. O> CO 00 CN t^ g ^H 11 r^ CO t- fl & w p4 9 & M 0) i- '""^ 1o minute PN o> oo O* t^ t O CO CO i-l CN IN CO CN o co oo t^ CN 1-1 CO Ol fl o S3 O 5 *? a 1. 1-1 CJ " ^ S R. a> E S d o> o fl 3 4) M s Oh^iffl r^f-ir 3 1 W rH CN CN t^ <3> 11 >-j rH 05 S * e 5 oo~ PQ O5 00 uO ffi 13 ^ cococo^o^ccirtdoo ' CO CO CO cs Q CNOt^- r- o oo o N c3 <" ?> -S -3g-s i w H 1-1 """' I-H CN 7-1 ->J* 00 rH r-o ^'53 ^-3^ ^ flgS j a 2 S.sp 01 X o> CO 3111 ^&.s M O is* i-it-ao cocoi-ico r -i CN CN 00 O5 r * i m w alfl g 6 CO CO 00 CN 10 . _ >> <0 w-g^^ 09 .- 3 4) v* i ,0 i-s 1-H '"' N IN 00 ^ W > 05 i 03 03 o3 < TJ W CJ V o o g 3 -g T) 1 ^ +a 4) ^fl 3 00~- 5 t^ i i H .3 ; oo' co ; ; ; ; ** 7 T3 ft"o fl a X 3 B "S w 2 - ^ C ^ s *S o ^ S "SON'S ^ H ^ -a p. g- J -2 . ^ =3^ s | ||1 | a-% 1^ "ts * ft-s^ ^ ^1 V* "* li* f .S .S S [H o 1 > ' ft o a 3 2 -a .M , a > -2 g a 3 3 -&5 1 3'"' -g i-i J ^ ^ oT oo 43 (^ "g fe-jdrioiS s s o S S M 8^9 ^^"0*0 "_g - a A -i -^ H -SH iT o-2 - Rais- ing of body (step- lift). CO Work due to step- lift. o X e (a) Total heat. Increment in heat above standing- value. W Total in- crease (t) Per hori- zontal kilo- gram- meter. Axl.OOO U) Per kilo- gram- meter of step- lift. h XI, 000 <*> Propor- tion of increase due to step-lift. 2.34 X100 c / i E. L. F. (Cont.) Jan. 24: Standing. . kg. meters. meters. kg. m. cols. 1.24 cals. gm.-cal. gm.-cals. p. ct. Walking . . 49.6 49.2 48.4 3,576 3,547 3,490 95.9 100.8 90.4 1.58 1.64 1.61 113.9 118.2 116.1 3.28 3.24 3.21 2.04 2.00 1.97 0.570 .564 .564 17.9 16.9 17.0 13 14 14 Average . H. M. S. Jan. 25: Standing . 72.1 49.1 95.7 1.61 2.00 .566 17.3 14 1 13 Walking. . . 44.6 42.2 41.6 2,944 2,785 2,746 79.2 76.2 76.0 1.74 1.68 1.70 114.8 110.9 110.2 2.97 2.78 2.79 1.84 1.65 1.66 .625 .592 .605 16.0 14.9 15.1 15 16 16 Average . Jan. 26: Standing . . . 66.0 42.8 77.1 1.71 1.72 .607 15.3 15 1.12 Walking . . . 53.5 52.7 52.3 3,520 3,468 3,441 90.4 77.2 83.2 2.36 2.34 2.37 155.3 154.0 155.9 3.18 3.07 3.04 . 2.06 1.95 1.92 .585 .562 .558 13.3 12.7 12.3 18 18 19 Average . 65.8 52.8 83.6 2.36 1.98 .568 12.8 18 In considering the data in tables 29 to 33 for the increment over the standing requirement, it should be remembered that, as explained on page 94, the standing metabolism was not obtained on each day that walking experiments were performed and whenever this was the case, an average value, or a value determined from a series of days nearest the time of the walking experiments, has been used. The selection of the standing values to be used on those days for which it was not de- termined has been a matter of some difficulty. Thus, H. R. R. on March 20 showed an unusually high standing metabolism. This value has been employed in computing the increase for walking on that day, but it has been considered that probably the measurements found on April 10 and 17 more nearly represent the normal basal metabolism for this man, and the average for these two days has been used in EXPERIMENTS WITH HORIZONTAL WALKING. 139 computing the increase on March 27, April 3, and 24, on which there were no standing experiments. TOTAL INCREMENT IN HEAT-PRODUCTION. The total increment in the heat-production above the standing requirement is assumed to represent the energy cost of the transporta- tion of the body-weight over a definite distance on the level as expressed in horizontal kilpgrammeters. As the amount of this total increment naturally depends upon the speed of walking, the values in column h are of but minor interest here, especially as theoretically no work is done hi this process and no efficiency value can be computed. It may be noted, however, that for moderate rates of walking, i. e., 50 to 60 meters per minute (approximately 2 miles an hour), the total in- crease for most of the subjects is a little less than double the standing requirement, with W. K. an apparent exception. E. D. B. shows for speeds of 95 to 100 meters per minute (approximately 4 miles an hour), an increase of nearly three times his requirement when he was stand- ing, while for a speed of 35 meters per minute the increase was about the same as for the standing requirement, or, stated in another way, when the walking was done at a rate of 35 meters per minute, only half of the total energy expended was due to the act of walking. INCREMENT IN HEAT PER HORIZONTAL KILOGRAMMETER. The main point of interest in tables 29 to 33 is the increment in the heat per horizontal kilogrammeter, as this shows the energy cost of walking 1 horizontal meter. This is later used to represent the hori- zontal component in the energy cost of grade walking. These values are given in column i of the several tables. For A. J. O., at a speed of approximately 63 meters per minute, the walking was done at a cost of from 0.416 to 0.501 gram-calorie per horizontal kilogrammeter, with an average value for the three days of 0.454 gram-calorie. (See table 29.) The data for H. R. R. show a range in the average values for cost per horizontal kilogrammeter from 0.643 gram-calorie on the first day to 0.574 gram-calorie on the last day. The first period of the first day (March 20) was marked by the fact that the largest energy cost for this subject was here found. As noted in the discussion of table 3, the highest standing metabolism for this subject was also found on this day. In spite of this high standing metabolism, the increase for the horizontal walking is greater than on the subsequent days. On the last two days of experimenting, H. R. R. seems to have walked at a less cost per horizontal kilogrammeter, but the data are too limited for the drawing of any conclusions as to the real betterment in this man's ability to walk with a smaller energy outlay as the time progressed. T. H. H., walking at a rate varying between 63 and 68 meters per minute, had an increase in the energy output per horizontal kilogram- 140 METABOLISM DURING WALKING. meter ranging between 0.512 gram-calorie on February 25 and 0.637 gram-calorie on April 5. The average increment on this basis for the 7 days was 0.579 gram-calorie. The daily average increase per hori- zontal kilogrammeter shows, if anything, a tendency to increase on the last 2 days, when the walking was done at a somewhat slower speed. The energy cost for consecutive periods shows no trend in any one direction. It can hardly be said that the subject walked regularly enough to develop any training effect, though it is to be assumed that acquaintance with the routine might have reduced any psychical effect or feeling of novelty. Of the 15 days during which W. K. walked on a level (see table 31), 13 days were in March, at the beginning of his use as a subject. Since there were no extreme differences in the speed of walking, the range being from 58 to 68 meters per minute on these days, they offer a fairly consecutive record from which comparisons may be expected. The range in the daily cost per horizontal kilogrammeter during March is from 0.574 gram-calorie on March 4 to 0.440 gram-calorie on March 31. (See table 31.) This decrease in the cost might be taken to indi- cate an improvement but for the fact that the change is very irregular, although as a rule the higher values are found in the first days of the month. Thus, the average for the first 7 days of experimenting in March is 0.516 gram-calorie and for the last 6 days it is 0.480 gram- calorie per horizontal kilogrammeter. It should also be noted that the last day on which W. K. was a subject (June 23), after 4 months of almost daily walking (see also table 15), his average cost per horizontal kilogrammeter was lower than that on any other day, namely, 0.409 gram-calorie. The results of the series might be taken to indicate, on the whole, a decrease in the cost per -horizontal kilogrammeter as this man continued his experiments. The average for the entire series of horizontal walking experiments with W. K. shows an expenditure over that for standing of 0.490 gram-calorie per horizontal kilogram- meter. In the case of E. D. B. the energy cost per horizontal kilogrammeter ranged from 0.603 gram-calorie on October 9, the first day of his walk- ing, to as low as 0.407 gram-calorie on November 24, while the average for the total 61 days is 0.478 gram-calorie. (See table 32.) To study the effect of training, the values for the same speeds have been grouped chronologically in table 34, so that the results for the different days will be comparable. The daily averages for both the total heat- output and the increment per horizontal kilogrammeter are given in this table. For the approximate speed of 55 meters per minute, the speed at which E. D. B. first walked, the cost per horizontal kilogram- meter fell quite consistently from 0.603 gram-calorie on October 9 to 0.407 gram-calorie on November 24. For a speed of 65 meters per minute there is also a fall between October 16 and December 13, EXPERIMENTS WITH HORIZONTAL WALKING. 141 though the change is not so great as with 55 meters per minute. The experiments at the speed of 77 meters per minute were first made late in October, and the effect of the training had already taken place to some extent. Moreover, at this speed, the subject was approaching TABLE 34. Daily values for metabolism of E. D. B., grouped chronologically on the basis of speed, to determine effect of training. (Values per minute.) In- In- In- Approxi- mate speed and date. Total heat- out- put. crease in heat per hori- zontal Approxi- mate speed and date. Total heat- out- put. crease in heat per hori- zontal Approxi- mate speed and date. Total heat- out- put. crease in heat per hori- zontal kg. m. kg. m. kg. m. 37 meters: cols. gm. cal. 55 meters cols. gm. cal. 72 meters: calf. gm. cal. Apr. 3 2.23 0.475 (cont.). Oct. 22 3.18 0.494 4 2.29 .522 Nov. 8 2.57 .451 23 3.23 .503 45 meters: 9 2.43 .420 25 3.22 .497 Oct. 30 2.36 .496 18- 2.47 .454 26 3.20 .503 Nov. 1 2.32 .474 23 2.42 .415 Dec. 2 2.90 .429 2 2.32 .489 24 2.45 .407 3 2.96 .444 3 2.26 .450 Mar. 29 2.88 .468 77 meters: 5 2.32 .460 31 2.71 .463 Oct. 27 3.34 .498 6 2.25 .435 Apr. 1 2.62 .466 28 3.30 .487 10 2.32 .443 65 meters: 29 3.39 .501 17 2.29 .452 Oct. 16 3.01 .510 Nov. 13 3.12 .455 22 2.35 .461 18 2.96 .483 15 3.18 .460 Dec. 4 2.21 .415 19 3.05 .503 16 3.17 .464 6 2.18 .410 20 3.09 .517 19 3.20 .477 7 2.27 .439 21 3.07 .517 Dec. 1 3.19 .466 55 meters: Nov. 11 2.89 .452 Mar. 22 3.36 .463 Oct. 9 3.26 .603 12 2.89 .459 Apr. 5 3.48 .488 11 2.99 .559 26 2.76 .429 10 3.57 .505 13 2.93 .539 Dec. 13 2.70 .425 91 meters: 14 2.85 .527 'Jan. 31 3.23 .531 Apr. 11 4.24 .547 15 2.84 .543 'Feb. 1 3.08 .455 12 4.19 .555 Nov. 4 2.48 0.447 Mar. 20 2.89 .436 13 4.48 .557 30 3.17 .489 'After recess of 3 weeks. the point which Durig has termed "the maximal efficiency speed," above which the energy cost increases in a faster ratio. In spite of these neutralizing factors, there is evidence of a fall in the energy cost between the end of October and the middle of November. The speed of 45 meters per minute was not used until October 30, but even these values indicate a decrease in the latter part of the series. It seems clear, therefore, that in the early horizontal-walking experiments with E. D. B., lack of practice or training was a factor in the energy require- ment. In this connection it should be noted that on January 31, on E. D. B.'s return from a three weeks' recess due to a lame foot, he had a much higher energy cost per horizontal kilogrammeter than at the end of his previous walking experiments. This may be an erratic result, for it may also be noted that on the second day following 142 METABOLISM DURING WALKING. the energy expenditure, though slightly above the average, was not in any way exceptional. From these considerations it may be seen that the value of 0.478 gram-calorie, while representing an average figure for this subject for the 61 days, does not show the energy cost for a trained subject. If we take the values found for December and March, and thereby elimi- nate the influence of the early data and also the extremely high and low speeds of April, an average value for the energy cost is obtained for E. D. B. of 0.446 gram-calorie. This is much lower than the aver- age value of 0.55 gram-calorie reported by Benedict and Mursch- hauser 1 in their summary of the work of earlier observers. But in many cases these average values for the earlier observers include experiments performed when the subjects were not in a strictly post- absorptive condition and in a few instances require an assumption of the respiratory quotient. Moreover, different techniques were em- ployed in the various researches. There is, therefore, no reason to believe that the value of 0.478 gram-calorie as an average for an un- trained subject over a considerable period or of 0.446 gram-calorie for a trained subject is exceptionally low. This effect of training finds support in the figures from the report of Benedict and Murschhauser, 2 although the authors themselves do not consider the evidence is sufficient to make any conclusion in the matter. It is seen from then- figures that their Subject I had a value of 0.507 gram-calorie as an average for 16 experiments made during a period of 1 month. The average for the 4 last days of this period, however, was 0.488 gram-calorie and for the first 5 days 0.515 gram-calorie. Also, then* Subject II in 57 experiments had an average cost per hori- zontal kilogrammeter of 0.493 gram-calorie 3 buf for the first 10 days of his experiments the average value was 0.506 gram-calorie, while for the last 6 days beginning with April 22, which was after 18 days of walking, the average value was 0.481 gram-calorie. These latter days, moreover, are when their subject was walking at a speed near the point of maximal efficiency. It is to be regretted that there were no horizontal-walking experi- ments with E. D. B. in the last part of December or the first part of January, when the standing metabolism of this subject was found to have risen to a higher level. (See p. 98.) But the fact that the energy cost per horizontal kilogrammeter for the approximate speeds of 55 to 77 meters per minute was as a rule higher during March or April than during the early part of December (see table 34) indicates that the increase in the metabolism shown by his standing requirements was also apparent in the cost per horizontal kilogrammeter*. 'Benedict and Murschhauser, Carnegie Inst. Wash. Pub. No. 231, 1915, p. 28. 'Benedict and Murschhauser, Ibid., p. 79. 'Benedict and Murschhauser, Ibid., p. 87. EXPERIMENTS WITH HORIZONTAL WALKING. 143 Of the other three subjects, J. H. G. expended on an average 0.533 gram-calorie per horizontal kilogrammeter, while it cost E. L. F. 0.562 gram-calorie and H. M. S. 0.588 gram-calorie per horizontal kilogram- meter. (See table 33.) These men were entirely untrained and did not walk long enough in these experiments to produce any training effect. The average cost per horizontal kilogrammeter of walking on a level, i. e., the increment over the standing requirement, irrespective of any training effect and at speeds mostly below 80 meters per minute, is as follows for each of the eight men included in this report : A. J. O., 0.454; H. R. R., 0.618; T. H. H., 0.579; W. K, 0.490; E. D. B., 0.478; J. H. G., 0.533; E. L. F., 0.562; H. M. S., 0.588 gram-calorie, with a general average of 0.538 gram-calorie. The most data were obtained with W. K. and E. D. B., and these men show the lower values. A. J. O., who likewise shows lower values, was also a well- trained subject, but with him there was only a limited amount of data. The average value of 0.538 gram-calorie for this group of 8 men is very close to the average value of 0.55 gram-calorie quoted by Benedict and Murschhauser in their summary of the work of other investi- gators previously referred to. Furthermore, taking into considera- tion the fact that the basal value used by the other investigators was in the majority of cases either a lying or a sitting value, the individual values for the 8 men studied hi the present research do not differ widely in range and character from those given by Benedict and Murschhauser 1 in their summary of previous work done on this sub- ject and already referred to. Although the average value for the group agrees with the average for the subjects of other investigators, the averages for the different men show the variations which may be expected for individual subjects. That these variations may be large is seen by comparing the average for the trained subject E. D. B. and the untrained but thoroughly cooperative subject H. M. S., between which there is a difference of nearly 25 per cent. 2 EFFECT OF SPEED UPON METABOLISM IN HORIZONTAL WALKING. In order to show more clearly the influence of the speed of walking upon the various factors observed, the data in tables 8 to 12 have been grouped according to certain arbitrary limits of 5 meters per minute and averaged. These averages are given in table 35, which also in- cludes the total increment and the increment per horizontal kilogram- meter, taken from columns h and i of tables 29 to 33, grouped and averaged in the same way. These groups of data represent values obtained in from 3 to 37 periods, but in most cases from 8 to 10 periods Benedict and Murschhauser, Carnegie Inst. Wash. Pub. No. 231, 1915, pp. 24-27. 2 The possible effects of weight and age as factors in this comparison should not be lost sight of, since H. M. S. was thinner than E. D. B., as well as older and taller. 144 METABOLISM DURING WALKING. have been averaged. At times consecutive periods of the same day fall into different groups if by chance the speeds of the different periods on that day are very near the dividing-line. Each group contains as a rule the results of several days which were in many cases quite widely distributed. TABLE 35. Metabolism during horizontal walking in experiments without food, grouped according to speed of walking. (Average values per minute.) Subject and speed, in meters. No. of periods. Average distance walked. No. of steps. Hori- zontal kilo- gram- meters of work done. Respira- tion- rate. Pul- monary venti- lation (re- duced). Body- tem- pera- ture. Blood- pres- sure. A. J. 0.: 60 to 65 6 meters. 63.0 '96 8 4,689 23.8 liters. 16.0 C. mm. H. R. R.: 60 to 65 11 60.9 97 1 4,364 17.3 14.8 65 to 70 4 67.1 103 3 4,932 18.0 16 4 T. H. H.: 60 to 65 7 63 2 99 6 3,621 S 14 2 11 4 65 to 70 14 67 1 104 1 3 828 14 6 11 4 W. K.: 55 to 60.. . 10 58.3 106 6 2,999 21.3 11.1 60 to 65 ... 19 62.9 109 8 3,247 20 8 10.8 65 to 70.. . 20 66.6 114 7 3 452 7 22 4 11 7 E. D. B.: 35 to 40.. 6 36.2 2,212 19.2 11.3 36.90 120 40 to 45 .. 13 43 8 79 5 2 578 18 7 11 1 45 to 50.. 22 46.3 80 6 2,722 19.5 11.5 50 to 55.. 55 to 60 .. 60 to 65.. 65 to 70.. 70 to 75.. 75 to 80.. 85 to 90.. 22 18 30 15 26 37 4 53.7 56.5 63.9 66.8 72.2 77.5 88.5 10 87.4 "89.7 "96.5 "98.4 "101. 6 "104.7 3,181 3,371 3,840 3,929 4,292 4,584 5,380 20.7 20.0 19.4 19.9 " 19.0 20.6 24.1 13.3 14.5 14.2 14.0 13.9 15.1 18.5 4 37.03 4 36.84 '37.18 U 37.13 14 36.90 3 37.12 37.25 4 125 4 124 17 120 14 119 14 122 3 125 130 90 to 100.. 5 96.0 5,849 23.9 20.1 37.28 130 J. H.G.: 50 to 55.. . 3 53.9 101 4 19 4 16 1 55 to 60. . . 6 55 4 92 3 18 7 15 5 E. L. F.: 45 to 50.. . 3 49 1 95 7 5 4 13 6 50 to 55 ... 6 52 6 *92 1 12 3 14 5 H. M. S.: 45 to 50... 3 42.8 77.1 17 5 12 1 50 to 55 ... 3 52.8 83 6 17 3 12 7 For footnotes, see facing page. EXPERIMENTS WITH HORIZONTAL WALKING. 145 TABLE 35. Metabolism during horizontal walking in experiments without food, grouped according to speed of walking. (Average values per minute.) Continued. Heat-output (computed). Subject and speed in meters. Pulse- rate. Carbon dioxide. Oxygen. Respira- tory quotient. *TI 4. 1 Due to Increase over standing. lotal. stand- ing. Total. Per h. kg. m. A. J. O.: c. c. c. c. cols. cals. cats. gm.-cal. 60 to 65 608 712 0.85 3.46 1.31 2.16 0.460 H. R. R.: 60 to 65... *104 670 833 .80 4.00 1.35 2.64 .605 65 to 70.. . 110 754 902 .84 4.47 1.39 3.08 .625 T. H. H.: 60 to 65 ... 100 559 S 651 .86 3.17 1.11 2.09 .577 65 to 70.. . *96 579 692 .84 3.36 1.11 2.23 .579 W. K.: 55 to 60.. . 75 426 519 .82 2.50 1.10 1.41 .469 60 to 65.. . 85 447 10 558 10 .80 2.68 1.08 1.60 .494 65 to 70... "84 493 7 589 T .84 2.86 1.13 1.72 .499 E. D. B.: 35 to 40.. 72 393 467 .84 2.26 1.17 1.10 .499 40 to 45.. 74 409 466 .88 2.28 1.08 1.20 .467 45 to 50.. 8 68 415 467 .89 2.29 1.08 1.21 .444 50 to 55.. 477 449 535 .84 2.59 1.09 1.49 .469 55 to 60.. 76 18 480 563 .85 2.73 1.13 1.61 .476 60 to 65 .. 1J 95 528 633 .83 3.06 1.15 1.92 .499 65 to 70.. 78 516 586 .88 2.87 1.16 1.78 .454 70 to 75.. i82 543 648 .84 3.14 1.08 2.07 .482 75 to 80.. *85 580 678 .86 3.31 1.09 2.11 .478 85 to 90.. 94 705 864 .82 4.17 1.19 2.97 .552 90 to 100.. 98 787 901 .87 4.40 1.17 3.22 .554 J. H. G.: 50 to 55.. . *98 537 697 .77 3.32 1.34 1.98 .529 55 to 60.. . ! 94 558 710 .79 3.40 1.34 2.06 .535 E. L. F.: 45 to 50.. . 100 544 674 .81 3.24 1.24 2.00 .566 50 to 55... 89 586 717 .82 3.46 1.31 2.15 .560 H. M. S.: 45 to 50... "93 451 601 .75 2.85 1.13 1.72 .607 50 to 55.. . "88 500 652 .77 3.11 1.12 1.98 .568 *5 periods. *10 periods. *6 periods. 4 4 periods. *9 periods. 12 periods. T 19 periods. 8 8 periods. 9 3 periods. 10 18 periods. 11 14 periods. 12 28 periods. 13 7 periods. M l period. U 25 periods.. 18 31 periods. 17 2 periods. 18 17 periods. EFFECT OP SPEED UPON TOTAL HEAT-OUTPUT. Considering first the total heat-output, we find in all cases an increase with each increase in speed, with the single exception of E. D. B. with a speed of 65 to 70 meters per minute. This exception is due rather to the excessive heat-output for the preceding group of values at 60 to 65 meters per minute. Two-thirds of the values at the latter speed were obtained during the early part of this subject's experience with the treadmill, namely, in October, while nearly all of the periods hi the 146 METABOLISM DURING WALKING. group for 65 to 70 meters were taken from experiments in the following months of November and December, when the effect of training had become apparent. This single exception to the effect of increase of speed gives evidence, therefore, of the effect of training in reducing the energy requirement. EFFECT OF SPEED UPON TOTAL INCREASE IN HEAT-OUTPUT. The energy-output over the standing requirement likewise increases with the increase in speed in much the same manner as was found with the total heat-output. This may be seen in the next to the last column of table 35 and graphically in figure 10. The high values for E. D. B. at 60 to 65 meters per minute, most of which were obtained early in the TABLE 36. Percentage increase in heat-output of E. D. B. due to walking on a level at various speeds. (Values per minute.) Range of speed. Horizontal kilogram- meters. Increase in heat over standing requirement. meters. p. ct. 35 to 40 2,212 94 40 to 45 2,578 111 45 to 50 2,722 112 60 to 55 3,181 137 55 to 60 3,371 142 60 to 65 3,840 167 65 to 70 3,929 153 70 to 75 4,292 192 75 to 80 4,584 194 85 to 90 5,380 250 90 to 100 5,849 275 Cerfs M ?ftO / s ?40 & ? " ??0 3.90 aoo 2.60 2.00 160 VOO Met r 200 180 160 140 120 100 HRR. r _v ^ [-0.8. * / / / lit. ^\ \y s - V _^T.H > ~s / HMS ,---" ./ ^ ^ >/ - t 4" *""^ -' ^ ws 40 45 50 55 60 65 70 75 80 85 90 95 100 FIG. 10. Increments in total heat-output over standing re- quirement for subjects walking on a level at different rates in meters per minute, with percentage increase (broken line) for E. D. B. EXPERIMENTS WITH HORIZONTAL WALKING. 147 study and show lack of training, are also apparent when the data are presented on this basis. The total increase in the heat-output, calcu- lated on the percentage basis, is given for E. D. B. in table 36. These figures show that for slow to medium speeds of walking (35 to 80 me- ters per minute, that is, not over 3 miles an hour), the per minute in- crease over the standing requirement ranged from 94 to 194 per cent, while for speeds above 80 meters per minute the percentage increase was from 250 to 275 per cent. These percentage values for the increase in the total heat have also been plotted for E. D. B. in the form of a dotted-line curve, and are included in figure 10. These increases in the energy-output are given for all of the subjects in table 37 on the basis of per meter increase in speed, and show that for all rates of walking below 80 meters per minute the increase in the heat-output varied on this basis from 0.024 calorie for E. D. B. to 0.071 calorie for H. R. R. The average for the group is 0.041 calorie. It is also seen from the detailed values for E. D. B. that for speeds below 57 meters per minute, each meter increase in speed required an increase in heat of 0.025 calorie, and from 57 to 78 meters per minute, the in- crease per meter was 0.024 calorie, while for speeds between 78 and 96 meters per minute, the increase per meter was nearly two and one- half times larger, namely, 0.060 calorie. TABLE 37. Heat-output over standing requirements per 1 meter increase in speed of horizontal walking. (Values per minute.) Subject. Range of average speed. 1 Increase in speed. Average increase in total heat- output due to increase in speed. Average heat increase per meter increase in speed. H. R. R meters. 60 . 9 to 67 . 1 meters. 6.2 cals. 0.44 cals. 0.071 T. H. H 63 . 2 to 67 . 1 3.9 .14 .036 W. K 68.3 to 66 6 8.3 .31 .037 E. D. B 36 . 2 to 77 . 5 41.3 1.01 .024 J. H. G 53 . 9 to 55 . 4 1.5 .08 .053 E. L. F 49 . 1 to 52 . 6 3.5 .15 .043 H. M. S 42 . 8 to 52 . 8 10.0 .26 .026 Average . . E. D. B 52.1 to 62. 7 36 . 2 to 66 . 5 10.7 20.3 .34 .51 .041 .025 56. 5 to 77. 5 77. 5 to 96.0 21.0 18.5 .60 1.11 .024 .060 'See third column, table 35. EFFECT OF SPEED UPON INCREASE IN HEAT PER HORIZONTAL KILOGRAMMETER. A summary for all of the subjects of the cost per horizontal kilogram- meter per minute as affected by the speed is given in table 38, in which are included the average results for the two subjects of Benedict and 148 METABOLISM DURING WALKING. Murschhauser, grouped according to like speeds. The table shows the wide variations which may be found with different subjects and also that no marked effect on this factor is evident below the speed of 80 to 90 meters per minute (approximately 3 miles an hour). These average values are likewise given in the form of curves for the five principal subjects. (See fig. 11.) TABLE 38. Average energy cost per horizontal kilogrammeler of walking on a level at different speeds. (Values per minute.) Subject. Energy cost (gm.-cal.) per h. kg. m. at various speeds. 35-40 meters . 40-45 meters . 45-50 meters . 50-55 meters . 55-60 meters . 60-65 meters . 65-70 meters . 70-75 meters . 75-80 meters . 85-90 meters . 90-100 meters . A. J. O. 0.460 H. R. R .605 .577 .494 .499 0.625 .579 .499 .454 T. H. H W. K 0.469 .476 .535 E. D.B 0.499 0.467 0.444 0.469 .529 .560 .568 0.482 0.478 0.552 0.554 J. H. G E. L. F .566 H. M. S .607 Average. . Subject I 1 .. . 0.499 .537 .505 .531 .493 .527 .539 .467 .482 .564 .513 .478 .509 .532 .552 .554 Subject II 1 . . .521 .498 . .527 .524 'Benedict and Murschhauser, Carnegie Inst. Wash. Pub. No. 231, 1915. GRAM- CALORIE 0.600 .550 00 .450 .400 METEI .-"- ^HR k *"- r.M H. , waes^ E.0.8. 9 _ ^ / y" *--v ^ ^~ ~^ V ,--* -^ TO 40 45 50 55 60 65 70 75 80 86 90 95 1C FIG. 11. Average energy cost per horizontal kilogrammeter of walking on a level at various distances per minute. From table 38 and figure 11 it is seen that an increase in speed is accompanied by an increase in the cost per horizontal kilogrammeter with H. R. R. and W. K., but practically no change was found for T. H. H. Table 38 also shows practically no change for J. H. G. and E. L. F., but with H. M. S. the cost per horizontal kilogrammeter fell. The curve of E. D. B. as a whole implies that there is practically no increase in the cost per horizontal kilogrammeter for medium speed, but for a speed above 80 to 85 meters per minute the cost increases. The group for the slowest speed, that for 35 to 40 meters per minute, shows a tendency to be higher than the succeeding groups, but these EXPERIMENTS WITH HORIZONTAL WALKING. 149 figures are the average of two days in April, while the averages for the two succeeding groups (40 to 45 meters per minute and 45 to 50 meters per minute) were from experiments made in November and December. The lapse of time between these groups is too great, therefore, to per- mit a statement that the cost increases as the speed falls below a cer- tain comfortable rate of walking. The effect of speed upon the energy cost per horizontal kilogram- meter can best be shown for E. D. B. by a consideration of the data for March and April, in which there is a wider range of speed and the influence of training is largely eliminated. These results are given in table 39, from which it is evident that for moderate speeds ranging from 55 to 77 meters per minute, the cost per horizontal kilogrammeter shows no tendency to change, but for speeds of 91 meters per minute the cost increased nearly 20 per cent. The latter speed was a forced one and required considerable exertion on the part of E. D. B. to maintain it. This increase in the energy cost is in full agreement with what Durig has claimed, namely, that the cost per horizontal kilo- grammeter is practically constant for speeds below 80 to 85 meters per minute, above which speed there is a break hi the curve and the energy- output increases at a faster ratio. TABLE 39. Energy cost per horizontal kilogrammeter with E. D. B. of walking on a level at different speeds in March and April 1916. (Values per minute.) Date. Approximate distance walked. Average heat perh. kg. m. 1916. Apr. 3 and 4 meters. 37 gm.-cal. 0.499 Mar. 29, 31, and Apr. 1 55 .466 Mar. 20 and 30 65 .463 Mar. 22, Apr. 5, and 10 77 .485 Apr. 11, 12, and 13 91 .553 In considering the extremely slow speed of 37 meters per minute, it is seen that on the two days of which 0.499 is the average the heat- output was 0.475 and 0.522 gram-calorie per horizontal kilogrammeter, respectively. These values are, unfortunately, not in close agreement. The high value of 0.522 gram-calorie for April 4 might be taken as sup- porting the statement of Frentzel and Reach, 1 that for slow restrained speeds there is an increase in the heat cost per horizontal kilogram- meter. This claim of Frentzel and Reach has been questioned by Durig, 2 who believes that there is not sufficient evidence in Frentzel and Reach's figures to support their statement. The value of 0.475 gram-calorie for April 3 lies close to the values found for all the other 'Frentzel and Reach, Archiv f. d. ges. Physiol., 1901, 83, p. 494. J Durig, Denkschrift. d. math.-natur. Klasse d. kaiserl. Akad. d. Wissensch., 1909, 86, p. 271. 150 METABOLISM DURING WALKING. days for speeds up to 78 meters per minute, with the exception of that of April 10, while the value of 0.522 gram-calorie on April 4 finds no support in the data for E. D. B. outside of the early experiments of October and that of January 31, when he resumed walking after an interval of three weeks. (See p. 141.) It seems probable that the value of 0.475 gram-calorie represents more nearly the true condition than does the value 0.522 gram-calorie, in which case it would appear to be in agreement with Durig's statement that there is no increase in the energy cost per horizontal kilogrammeter for slow walking. Ob- viously a study of the energy demands for extremely slow walking, i. e., sauntering, would be of considerable physiological interest. Our results do not include those for the highest speeds of walking, as during severe grade walking slow speeds must necessarily be em- ployed. In any consideration of the literature on horizontal walking special attention should certainly be given to the series of experiments of Liljestrand and Stenstrom, 1 in which the Douglas bag was used. With both subjects, N. S. and G. L., the energy (expressed as oxygen consumption) per horizontal kilogrammeter shows an astonishingly uniform agreement with all of the best earlier work. Since in some instances, at least, the actual duration of these experiments was but 42 seconds, this speaks for not only the great applicability of the Douglas-bag method, but likewise for the extraordinary technical skill of the Swedish investigators. This series of experiments fully sub- stantiates Douglas's conclusions as to the applicability of his bag method to studies of the metabolism during exercise. EXPERIMENTS WITH SUBJECT "MARKING TIME." For comparison with the energy requirements of horizontal walking, it seemed of interest to secure a few measurements when the subject simply "marked time," as representing a degree of activity interme- diate between standing and walking. Data were therefore obtained with W. K. which are given in table 40. In marking time, the subject kept his legs nearly straight, flexing them as little as possible at the knees. He swung the leg mostly from the hip, thus lifting the body the minimum amount, and although there was some lifting of the limbs, it was not like the regulation marking time of the army. This movement was made at an average rate of 101 so-called "steps" per minute. Under these conditions the average metabolism per minute of W. K. was : carbon dioxide, 414 c. c. ; oxygen, 500 c. c. ; heat, 2.42 cals. By consulting table 35, page 144, it is seen that these values cor- respond very nearly to his requirement for horizontal walking at a speed of 55 to 60 meters per minute, with steps taken at the rate of 106.6 per minute, the heat-output differing only about 3 per cent. It would seem that the energy necessary for horizontal walking is almost Liljestrand and Stenstrom, Skand. Archiv f. Physiol., 1920, 39, pp. 178 and 179. EXPERIMENTS WITH HORIZONTAL WALKING. 151 wholly confined to that for the muscular effort of the lower limbs, while the oscillations of the trunk hi keeping the body balance play a minor role. This finds confirmation in some experiments reported by Waller 1 on the carbon-dioxide production during horizontal walking. In a graph showing the carbon-dioxide output for different rates of walking, he also includes that for marking time at a rate of 120 steps per minute. He does not discuss this portion of the curve, and it is probable that the form of marking time was different from that which we used. However, the carbon-dioxide output indicated by his curve seems to TABLE 40. Metabolism of W. K. while "marking time" in experiments without food. (Values per minute). Date. No. of steps. Average respiration- rate. Average pulmonary ventilation (reduced). Average pulse- rate. 1 Carbon dioxide. Oxygen. Respira- tory quotient. Heat-out- put (com- puted) . 1915. June 3 92.2 23.3 liters. 15.6 74 c. c. 420 c. c. 485 0.87 cals. 2.37 97.2 100.4 100.4 23.3 23.1 23.0 15.9 15.3 15.4 74 76 79 429 405 416 512 487 489 .84 .83 .85 2.48 2.36 2.38 Average . . 97.6 23.2 15.6 76 418 493 .85 2.40 June 4 99.2 22.9 15.1 74 410 485 .85 2.36 22.0 15.0 74 430 507 .85 2.47 105.0 104.2 22.2 22.2 14.8 14.6 77 75 419 409 500 508 .84 .81 2.43 2.45 Average . . 102.8 22.3 14.9 75 417 500 .84 2.43 June 5 102.0 22.1 14.8 75 412 500 .83 2.42 103.4 104.4 104.0 21.7 21.5 21.8 14.3 14.1 14.3 77 77 78 408 401 409 515 494 515 .80 .81 .80 2.47 2.38 2.47 Average. . 103.5 21.8 14.4 77 408 506 .81 2.44 See table 27 (page 111) for additional records for pulse-rate of W. K. while he was "marking time. be very close to the requirement of the subject when walking at a speed of 92 meters per minute, or 130 steps per minute, viz, an output of 972 c. c. of carbon dioxide for marking time and 960 c. c. for walk- ing. That is, the carbon-dioxide requirement for marking time at 120 steps and walking at 130 steps differed only by 1 per cent. In their study with army recruits, Cathcart and Orr 2 included obser- vations of the respiratory exchange with a subject "marking time." In 10 experiments after meals of varying composition and with the man carrying loads varying from 5 to 20 kg., the total heat-output varied from 209 to 271 calories per hour. The standing value was about 75 calories per hour. 3 The tempo was 100 beats per minute. J Waller, Journ. Physiol., 1919, 53, Proc. Physiol. Soc., p. xxiv. 'Cathcart and Orr, Energy expenditure of the infantry recruit in training. Office, London, 1919. (See table 47.) 'See subject M, tables 7 and 8 of Cathcart and Orr, loc. cit. H. M. Stationery 152 METABOLISM DURING WALKING. They note that the energy cost of "marking time" was with the three greatest loads (16, 21, and 26 kg.) higher than that for slow marching at 62.5 yards (57.2 meters) per minute, and with a load of 11 kg., "marking time" called for almost identically the same energy-output as a slow march of 57.14 meters per minute. A most significant dis- cussion of "marking time" is presented by Cathcart and Orr. 1 The energy requirement for "marking time" is considerably larger than one would anticipate and shows that unnecessary and extraneous movements might easily lead to considerable differences in the metab- olism measurements with muscular work of a moderate degree of intensity. Benedict and Murschhauser 2 have called attention to this in some measurements in which their subject stood and swung his arms and hands as in fast walking, with the result that there was an increase of 126 per cent over his quiet standing metabolism. STEPS AND STEP-LIFT DURING HORIZONTAL WALKING. As was stated in an earlier section (p. 33), a record was kept of the number of steps the subject took in walking, and measurements were frequently made of the height to which the subject lifted his body as a result of the heel-and-toe action in walking. These records are given in detail in tables 29 to 33. The daily averages are summarized according to the speed of walking in table 41, in which the average length of step is also included. It is believed that the number of steps taken is accurately known, and therefore the average length of step is without appreciable error. This can not be so fully claimed, however, for the height of the step-lift, as will be shown later. (See p. 155.) TABLE 41. Number of steps and height of step-lift in walking on a level. (Values per minute.) Subject and date. Distance walked. No. of steps. Step-lift. Step-lift per step. Length of step. A. J. O.: Mar. 2 meters. 62.7 96.8 meters. 2.09 cm. 2.16 cm. 64.8 Feb. 24 63.5 96.9 1.87 1.93 65.5 H. R. R.: Apr. 17 60.0 98.1 1.05 1.07 61.2 3 60.5 95.3 1.11 1.16 63.5 24 60.7 98.3 1.20 1.22 61.7 10 61.1 99.0 1.02 1.03 61.7 Mar. 20 66.1 103.8 .92 .89 63.6 27 66.8 102.6 1.35 1.32 65.1 T. H. H.: Apr. 5 62.8 100.2 1.79 1.79 62.7 Feb. 25 63.6 99.0 1.61 1.63 64.2 Mar. 30 65.4 101.3 2.03 2.00 64.6 19 66.8 106.4 1.73 1.63 62.8 26 67.2 101.3 2.13 2 10 66.3 22 67.5 105.8 1.29 1.22 63.8 24 67.8 104.2 1.83 1.76 65.1 'Cathcart and Orr, loc. tit., p. 54. *Benedict and Murschhauser, Carnegie Inst. Wash. Pub. No. 231, 1915, pp. 71 and 97. EXPERIMENTS WITH HORIZONTAL WALKING. 153 TABLE 41. Number of steps and height of step-lift in walking on a level. (Values per minute.) Continued . Subject and date. Distance walked. No. of steps. Step-lift. Step-lift per step. Length of step. W. K.: June 23 meters. 57.1 106.5 meters. 1.28 cm. 1.20 cm. 53.6 Mar. 18 60.1 104.6 1.01 .97 57 5 16 60.8 108.3 .81 .75 56.1 13 62.1 110.6 1.07 .97 56.1 9 62.3 110.2 .97 .88 56.5 29 62.3 109.3 1.17 1.07 57.0 12 62.5 112.9 1.21 1.07 55.4 4 64.3 114.5 1.27 1.11 56.2 Feb. 26 64.4 114.7 1.40 1.22 56.1 Mar. 31 65.1 108.8 1.18 1.08 59.8 23 65.7 112.1 1.28 1.14 58.6 5 65.8 115.0 1.55 1.35 57.2 8 66.5 116.1 1.49 1.28 57.3 25 67.3 112.7 2.03 1.80 59.7 17 67.5 116.2 1.46 1.26 58.1 E. D. B. Nov. 2 43.2 79.9 .70 .88 54.1 Oct. 30 43.9 80.3 .66 .82 54.7 Nov. 1 44.3 79.7 .72 .90 55.6 3 44.5 85.3 .76 .89 52.2 Dec. 6 45.0 78.5 .68 .87 57.3 Nov. 17 45.7 79.0 .78 .99 57.8 Dec. 7 45.8 77.1 .67 .87 59.4 Nov. 6 45.9 80.8 .75 .93 56.8 5 46.2 81.9 .81 .99 56.4 Dec. 4 46.7 79.0 .93 1.18 59.1 Nov. 22 47.4 80.7 .79 .98 58.7 10 47.8 84.7 1.00 1.18 56.4 4 53.5 86.5 1.17 1.35 61.8 Oct. 15 54.4 88.8 1.15 1.30 61.3 14 54.5 88.1 1.34 1.51 61.9 Nov. 9 54.7 88.0 1.19 1.35 62.2 23 54.8 87.7 1.26 1.44 62.5 Oct. 11 55.0 92.9 1.40 1.51 59.2 Nov. 18 55.0 88.3 1.21 1.37 62.3 Oct. 13 55.8 87.0 1.34 1.54 64.1 Nov. 8 56.1 89.0 1.26 1.42 63.0 Oct. 9 57.1 93.0 1.30 1.40 61.4 Nov. 24 57.5 90.0 1.37 1.52 63.9 Jan. 31 63.2 96.0 2.50 2.60 65.8 Feb. 1 63.6 94.2 2.23 2.37 67.5 Oct. 21 63.8 97.3 1.87 1.92 65.6 18 64.3 96.4 1.78 1.85 66.7 19 64.3 96.5 1.83 1.88 66.6 20 64.6 97.6 1.87 1.92 66.2 16 65.0 97.6 1.73 1.77 66.6 Nov. 26 65.9 98.3 1.66 1.69 67.0 Dec. 13 66.7 97.6 2.07 2.12 68.3 Nov. 12 67.1 99.1 1.92 1.94 67.7 11 67.9 99.0 2.46 2.48 68.6 Dec. 3 71.3 101.9 2.56 2.52 70.0 2 71.6 101.8 2.49 2.45 70.3 Oct. 23 72.2 101.1 2.13 2.12 71.4 22 72.3 100.5 2.06 2.05 71.9 26 72.9 102.4 2.47 2.41 71.2 25 73.2 101.4 2.50 2.47 72.2 Dec. 1 76.2 105.3 2.72 2.58 72.4 154 METABOLISM DURING WALKING. TABLE 41. Number of steps and height of step-lift in walking on a level. minute.) Continued. (Values per Subject and date. Distance walked. No. of steps. Step-lift. Step-lift per step. Length of step. E. D. B. Con. Nov. 13 meters. 76.7 103.9 meters. 2.75 cm. 2.65 cm. 73.8 16 76.9 103.7 2.90 2.80 74.2 15 77.0 104.0 2.83 2.72 74.0 Oct. 27 77.7 104.5 2.91 2.78 74.4 28 77.8 106.5 2.78 2.61 73.1 Nov. 19 77.9 104.1 2.43 2.33 74.8 Oct. 29 78.0 104.8 2.95 2.81 74.4 J. H. G.: Jan. 19 54.7 101.0 1.65 1.65 54.2 18 55.0 88.1 1.31 1.49 62.4 20 55.0 97.1 1.71 1.75 56.6 E. L. F.: Jan. 24 49.1 95.7 1.61 1.69 51.3 21 52.4 90.3 1.78 1.97 58.0 22 52.8 94.9 1.79 1.79 55.6 H. M. S.: Jan. 25 42.8 77.1 1.71 2.22 55.5 26 52.8 83.6 2.36 2.82 63.2 NUMBER OF STEPS IN HORIZONTAL WALKING. In adapting himself to a definite speed, the subject may either change his length of stride or the number of his steps, and, in fact, he does both. It is to be expected that for slower speeds there will be fewer steps, also that the strides will be shorter; but even for the same speed it is seen that on different days there is a change in both the number and length of steps. This difference amounts in some cases to as much as 6 or 7 steps per minute. W. K., who was the shortest subject, shows the most steps per minute for a given speed, the number of steps at a speed of 67.5 meters being 10 more per minute than the number for T. H. H. at the same speed and 14 more than for H. R .R., the tallest subject, at approximately the same rate of walking. On the other hand, E. D. B., who was shorter than H. R. R., took even fewer steps per minute than the latter, as may be seen by comparing the data for November 26 and December 13 for E. D. B. with those for March 20 and 27 for H. R. R. These variations make it impossible to draw any definite conclusions even for the same subject. One can only say that a man, walking at normal and constant speed, may unconsciously alter his gait four or more steps per minute, and although the difference between individuals depends in a large measure upon the length of leg of the subjects, it is possible for a shorter man to take natural strides which are longer than those taken by a taller individual. The number of steps repre- sents to a certain degree the amount of effort exerted hi walking, but evidently, at least with these subjects and the rates of speed here used, the number does not appear to be proportional to the energy expended. EXPERIMENTS WITH HORIZONTAL WALKING.* 155 The average number of steps taken by E. D. B. at different speeds is shown in table 42. (See p. 156.) The increase in the number of steps with greater speed is not regular, but shows a diminishing rate as the speed increases. Thus, the number of steps was 8.4 greater for 55 meters per minute than for 45 meters per minute, or an increase of 0.84 step for each meter per minute increase in speed, and 0.82 step when the speed became 65 meters per minute. The increase to 72 and 77 meters per minute was accompanied by an increase of practically 0.62 per meter increase in speed hi each case. With E. D. 3., there- fore, the increase in the speed of walking appears to have been more nearly taken care of at the lower speeds by an increase in the number of steps, but with the higher speeds this became a lessening factor. STEP-LIFT DURING HORIZONTAL WALKING. In considering the data recorded in tables 29 to- 33 for the elevation of the body, or what we have termed the step-lift, it is recognized that there are considerable variations in this factor for the same subject at the same speed on different days, and also that substantial differences appear at times for the same subject in the periods for the same day. This would naturally lead to a questioning of the technique by which the measurements were made. POSSIBLE CAUSES FOR VARIATION IN STEP-LIFT. The most apparent fault in the technique whiqh would lead to these differences in the records would be a failure to have the fork of the recording device (see fig. l,p. 19) held firmly against the shoulder of the subject, thereby not giving the full effect of the step to the counter. It is, of course, possible that an error may have occurred in this way in a few instances, but as it was recognized that such difficulty might occur we were especially careful to be on the watch for it. Another source of error would be in the slipping of the cord on the periphery of the wheel which operated the counter, This would naturally produce too low a registration. This, we know, did occur in a few instances, and in such cases we have made use of the kymograph record in estimating the lift. After such conditions were discovered, it was the practice to rub a little powdered rosin on the cord at the beginning of each period. Even with this precaution and when no slipping was apparent, dif- ferences were still found in the elevation. It seems probable, there- fore, that this difference was due to the gait of the subject, produced either by more shoulder-motion or by a lateral swaying of the body or by a difference in the absolute lift. It should be recalled that if a subject, while taking 100 steps a minute, lifted his body 1 cm. a step, it would require a displacement of only 2 mm. from any cause to produce a variation of 20 per cent in the final reading. That the subject changed his gait by changing the number and length of his steps has been shown in the preceding section, but how much this change in the 156 METABOLISM DURING WALKING. measured step-lift is due to one or the other of these causes we do not know. Though these differences make the measurements of less con- sequence, nevertheless we believe that the values obtained have enough interest to present. TOTAL STEP-LIFT PER MINUTE. A survey of the figures in tables 29 to 33 and 41 shows that for the ranges of speed employed the step-lift per minute varied approxi- mately from 1 to 3 meters, and that a tall man like H. R. R. had a total lift per minute of about the same degree as that of a short man like W. K., who had to take more steps to cover the same distance The relation of speed to the step-lift is best shown by the results obtained for E. D. B., with whom a larger amount of data was obtained. (See table 41.) It may be of interest to note the average values on the basis of speed. This comparison is made for E. D. B. in table 42, in which we find that the average per minute step-lift at 45 meters per minute was 0.77 meter; for 55 meters, 1.27 meters; for 65 meters, 1.99 meters; for 72 meters, 2.37 meters; and for 77 meters, 2.78 meters. TABLE 42. Relationship between step-lift and speed of walking in horizontal-walking experi- ments without food with E. D. B. (Values per minute.) Increment Total Average speed, in meters. Range in total step-lift. Average total step-lift. in total step-lift per meter increase step-lift per meter of distance Average No. of steps. Average step-lift per step. in speed. walked. meters. meters. cm. cm. - cm. 45 . 66 to 1 . 00 0.77 1.71 80.6 0.96 55 1.15 to 1.40 1.27 5.0 2.31 89.0 1.43 65 1.66to2.50 1.99 7.2 3.06 97.2 2.05 72 2. 06 to 2. 56 2.37 5.4 3.29 101.5 2.34 77 2. 43 to 2. 95 2.78 8.2 3.61 104.6 2.66 But of special significance is the increment in the total step-lift per minute due to each meter change in speed. In passing from a speed of 45 to 55 meters per minute, the total step-lift per minute increased on the average for each meter increase in speed 5 cm. ; from 55 to 65 meters, 7.2 cm. ; from 65 to 72 meters (a change in speed of but 7 me- ters), the increment was 5.4 cm.; and from 72 to 77 meters (a change in speed of only 5 meters), the increase in the total step-lift was 8.2 cm. per meter increase in speed. These increments per meter increase in speed, which are given in table 42, show rather extraordinary irregu- larity hi the values. Finally, we should observe the step-lift per meter of distance trav- eled. It is seen that at 45 meters per minute the step-lift was 1.71 EXPERIMENTS WITH HORIZONTAL WALKING. 157 cm. per meter; at 55 meters, 2.31 cm. ; at 65 meters, 3.06 cm. ; at 72 me- ters, 3.29 cm.; and at 77 meters, 3.61 cm. These values show, there- fore, that the step-lift per meter of distance traveled was somewhat less at the lower speeds. This fact is contrary to the evidence in several of our experiments, from which it appeared that the energy expendi- ture per horizontal kilogrammeter tended to be somewhat greater at the extremely slow speeds. This again emphasizes the importance of studying more in detail the physiology of walking at slow or "saunter- ing" speeds. STEP-LIFT PER STEP. It is possible that the change in number and length of steps to obtain a desired speed might not affect the lift per step and that it would re- main relatively uniform. An inspection of the figures for the lift per step in table 41 shows that the same variations are present here that were found in the number of steps and in the total step-lift per minute. Not only are there variations between individuals for the same speed, but for the same individual at the same speeds on different days varia- tions appear which, though not large in themselves, amount to as much as 20 per cent of the total step-lift per minute. Thus W. K., walking at a speed of 62.3 meters per minute, had a step-lift per step on March 9 of 0.88 cm. and on March 29 of 1.07 cm., with a difference of 0.19 cm., or 21 per cent. With the faster speeds, the step-lift is greater when the extreme speeds are compared, but with the slower speeds there are numerous instances when there was a greater step-lift per step than with speeds a few meters faster. In the long series with E. D. B. it appears that all speeds over 70 meters per minute were accompanied by a step-lift per step of 2 cm. or more, and with two exceptions, speeds under 50 meters per minute had a step-lift per step of less than 1 cm. The high values for January 31 and February 1, 1916, fall quite out of the regularity of the series. The conditions involving the indi- vidual gaits are apparently too complex for a simple analysis, and only general impressions can be obtained from the measurements. Table 42 also shows the average step-lift per step for E. D. B. with change in the average speeds. Here, as in the case of the total step- lift per meter distance, there is an absence of uniformity in the amount of increase in the step-lift, though the increase is progressive in each instance. ENERGY INCREMENT DUE TO WORK OP STEP-LIFT. By multiplying the step-lift as given in meters by the body-weight of the subject, it is possible to obtain the kilogrammeters of work done due to this elevation of the body. 1 From this the heat-output per kilogrammeter of step-lift has been computed. (See column / of 'It is most important to note that the effort of sustaining and lowering the body is entirely dis- regarded in this calculation. 158 METABOLISM DURING WALKING. tables 29 to 33.) By using the factor 426.6 for the mechanical equiva- lent of heat, 1 we may likewise compute the probable proportion of the increment in the heat-output which was due to the work of the step- lift. These percentages are given for each experiment in the last column of tables 29 to 33, in which 2.34 gram-calories is taken as the heat equivalent of 1 kg. m. Thus, by reference to table 29, we find that A. J. O., with a body- weight of 75 kg. and walking at a speed of 63.1 meters per minute, accomplished on February 24 in the first period 4,733 h. kg. m. per minute, and by his steps lifted his body to an elevation of 1.72 meters in 1 minute, thus performing 129 kg. m. of work. His standing basal metabolism for this day was 1.30 calories per minute. His walking metabolism for this period was 3.67 calories. The increase due to the walking was therefore 2.37 calories, which is equivalent to 0.501 gram- calorie per horizontal kilogrammeter, and 18.4 gram-calories per kilo- grammeter of work for the step-lift. The values for the energy cost of this work of lifting the body (see column j, tables 29 to 33) show expenditures from as high as 47 gram- calories per kilogrammeter for H. R. R. to as low as 12 gram-calories for E. D. B. The average cost per kilogrammeter of step-lift for A. J. O. is 15.3 gram-calories, with a percentage of increment due to the elevation of the body of 14 to 17 per cent. The percentage of incre- ment for H. R. R. is as low as 5 per cent on his first day of walking and does not exceed 8 per cent at other tunes. With T. H. IJ. the average cost per kilogrammeter due to step-lift was 22.1 gram-calories, and the average percentage of increment 11 per cent. The values for W. K. show considerable variation, the elevation of the body ranging in the periods between 0.7 and 2.07 meters per min- ute, with the amount of work done varying between 36.8 and 104.5 kilo- grammeters. The least amount of work done was on March 16, and these values are so much less than the other values for this subject that they may fairly be questioned. The original records show nothing, however, to indicate any defect in the technique to account for this variance. The average heat-output per kilogrammeter due to step- lift was 25.5 gram-calories, with considerable variation from day to day. The daily average for the percentage of increment due to step- lift ranged from 6 per cent on March 16 to 14 per cent on March 25. The average for the first 6 days in March was 9 per cent and of the last 6 days 10 per cent, but this difference is not sufficient to imply any improvement in this respect, as these figures can at best be considered as only approximate. 'Armsby, Principles of animal nutrition, New York, 2d ed., 1906, p. 233. A so-called "best" value of 426.7 is reported in the Smithsonian Physical Tables, Washington, 1920, 7th rev. ed., table 212, p. 197. Our computations were made previous to the publication of this edition by means of the slightly lower figure. EXPERIMENTS WITH HORIZONTAL WALKING. 159 For the subjects as a group, with walking at average speeds, the percentage increments due to step-lift range usually from 8 to 14 per cent, while with higher speeds a value for E. D. B. was found of 18 or 19 per cent. Benedict and Murschhauser 1 report a step-lift of 3.78 meters for their Subject I while he was walking at a speed of 75.9 me- ters per minute. Since his body- weight was 73. 1 kg., this corresponded to a work equivalent of 276.32 kilogrammeters, or an energy require- ment of 0.65 calorie per minute, which was approximately 23 per cent of the total energy increment due to walking. This value is much TABLE 43. Effect of training on step-lift and on proportion of heat-output expended in such movement. Subject, E. D. B., horizontal-walking experiments without food. October SO, 1916, to February 1, 1916. (Values per minute.) Date and speed. Average step-lift. Proportion of increase in heat due to step-lift. Date and speed. Average step-lift. Proportion of increase in heat due to step-lift. 43 to 48 meters: meters. p. ct. 60 to 68 meters: meters. p. ct. Oct. 30. 0.66 7 Oct. 16. . 1.73 12 Nov. 1. .72 8 18. . 1.78 14 2. .70 8 19. . 1.83 13 3. .76 9 20. . 1.87 13 5. .81 9 21. . 1.87 13 6. .75 9 Nov. 11. . 2.46 19 10. 1.00 11 12. . 1.92 15 17. .78 9 26. . 1.66 14 22. .79 9 Dec. 13. . 2.07 17 Dec. 4. .93 11 Jan. 31. . 2.50 17 6. .68 9 Feb. 1 . . 2.23 18 7. .67 8 71 to 73 meters : 52 to 58 meters: Oct. 22. . 2.06 14 Oct. 9 . 1.30 9 23. . 2.13 14 11. 1.40 11 25. . 2.50 16 13. 1.34 10 26. . 2.47 16 14. 1.34 11 Dec. 2 . . 2.49 19 15. 1.15 9 3. . 2.56 19 Nov. 4 . 1.17 12 76 to 78 meters: 8. 1.26 12 Oct. 27. . 2.91 18 9. 1.19 12 28. . 2.78 17 18. 1.21 11 29. . 2.95 18 23. 1.26 13 Nov. 13. . 2.75 19 24. 1.37 14 15. . 2.83 19 16. . 2.90 19 19. . 2.43 15 Dec. 1 . . 2.72 18 higher than that found for any of our subjects, the nearest approach to it for similar speed being that for E. D. B., who, on December 1, walked at a speed of 76.2 meters per minute, with a step-lift of 2.72 meters per minute, using 18 per cent of the heat expended for horizontal progression in the step-lift. The effect of training on the step-lift and on the heat-output due to this factor may be studied by reference to table 43, in which have been Benedict and Murschhauser, Carnegie Inst. Wash. Pub. No. 231, 1916, p. 80. 160 METABOLISM DURING WALKING. grouped the average step-lift per day for various speed groups and also the percentage of the heat-output expended due to this step-lift. An inspection of these figures shows no uniform change in the step- lift for a definite speed as the experiments continued, except possibly with the 60 to 68 meter group. In several groups, the percentage of the increment in the heat-output due to the step-lift increased somewhat as time progressed. As has already been seen in other groupings of the results, these figures show that as the speed increased, the step-lift also increased, likewise the percentage of the increment in heat due to the step-lift. The above consideration of the step-lift suggests several important lines of study, for if the step-lift involves a minimum of from 10 to 20 per cent of the energy required above basal for the work of forward pro- gression, it can readily be seen that a type of gait which would mini- mize the step-lift would tend to decrease this factor. Doubtless the time relations of elevation, sustained suspension, and lowering of the body in typical and atypical gaits would throw much light on this important problem of efficient and economical horizontal walking. That such a study should likewise consider the gait in grade walking is obvious. It is the current practice of experienced mountaineers to alter their gait frequently. PHYSIOLOGICAL EFFECTS OF HORIZONTAL WALKING. As was done in the standing experiments, records were obtained in these walking experiments of the respiration-rate, pulmonary ventila- tion, pulse-rate, and, in some of the experiments, especially with E. D. B., the body-temperature and blood-pressure. The detailed records are given in the statistical tables 8 to 12,- and the daily averages grouped according to speed in table 35. A summary is also given in table 44, in which not only the averages for the speed groups are given, but also the number of experimental periods on which the speed-group data are based, and the increments due to the activity of walking. These increments have been calculated by using as a basal value for each subject the average of the values obtained in his standing experi- ments. (See tables 3 to 7.) RESPIRATION-RATE DXTRING HORIZONTAL WALKING. From tables 8 to 12, and 35, and the summary in table 44, it is seen that individual subjects show wide individual differences. For the same subject the increase in the respiration-rate for the moderate speeds of walking was gradual and no larger than the variations in the results for an individual with a definite speed. This applies with E. D. B. up to an average speed of 77.5 meters per minute, but above this speed the respiration-rate increased more rapidly. Thus, the increment above the standing rate was increased 1.9 respirations for EXPERIMENTS WITH HORIZONTAL WALKING. 161 an increase in average speed from 43.8 to 77.5 meters per minute, while with an increase in speed from this point to 96.0 meters per minute, the increment in the respiration over the standing increased 3.3 respira- tions. The respiration-rate of E. L. F. was of marked peculiarity on the two days of January 22 and 24 as compared with the rate on January 21. (See table 12, p. 68.) On all three days the respiration tracings shown on the kymograph for the standing periods were normal and not dissimilar to those of the other subjects. This was also the case with his walking periods on January 21, but in his walking periods of January 22 and 24 there was a marked change, the rates falling to 5 to 8 per minute, while the volume per respiration (unreduced), as meas- TABLE 44. Increments in various physiological factors due to walking on a level in experiments without food. (Values per minute.) Nn nf Respiration-rate. Pulmonary ventilation (reduced). I 1 ! U. VI Average Subject and speed. experi- mental periods. distance walked. Average. Increase over Average. Increase over standing. standing A. J. O.: meters. liters. liters. 60 to 65 meters . . 6 63.0 23.8 2.0 16.0 8.2 H. R. R.: 60 to 65 meters . . 11 60.9 17.3 1.8 14.8 7.8 65 to 70 meters . . 4 67.1 18.0 2.5 16.4 9.4 T. H. H.: 60 to 65 meters . . 7 63.2 14.2 1.3 11.4 4.9 65 to 70 meters . . 14 67.1 14.6 1.7 11.4 4.9 W. K.: 55 to 60 meters . . 10 58.3 21.3 .2 11.1 4.6 60 to 65 meters . . 19 62.9 20.8 -.3 10.8 4.3 65 to 70 meters . . 20 66.6 22.4 1.3 11.7 5.2 E. D. B.: 35 to 40 meters . 6 36.2 19.2 3.8 11.3 2.2 40 to 45 meters . 13 43.8 18.7 3.3 11.1 2.0 45 to 50 meters . 22 46.3 19.5 4.1 11.5 2.4 50 to 55 meters . 22 53.7 20.7 5.3 13.3 4.2 55 to 60 meters . 18 56.5 20.0 4.6 14.5 5.4 60 to 65 meters . 30 63.9 19.4 4.0 14.2 5.1 65 to 70 meters . 15 66.8 19.9 4.5 14.0 4.9 70 to 75 meters . 26 72.2 19.0 3.6 13.9 4.8 75 to 80 meters . 37 77.5 20.6 5.2 15.1 6.0 85 to 90 meters . 4 88.5 24.1 8.7 18.5 9.4 90 to 100 meters. 5 96.0 23.9 8.5 20.1 11.0 J. H. G.: 50 to 55 meters . . 3 53.9 19.4 3.1 16.1 5.5 55 to 60 meters . . 6 55.4 18.7 2.4 15.5 4.9 E. L. F. : 45 to 50 meters . . 3 49.1 5.4 -9.6 13.6 3.0 50 to 55 meters . . 6 52.6 12.3 -2.7 14.5 3.9 H. M. S.: 45 to 50 meters . . 3 42.8 17.5 .6 12.1 2.1 50 to 55 meters . . 3 52.8 17.3 .4 12.7 2.7 162 METABOLISM DURING WALKING. TABLE 44. Increments in various physiological factors due to walking on a level in experiments without food. (Values per minute.) Continued. Subject and speed. Pulse-rate. Body-temperature. Blood-pressure. Average Increase over standing. Average. Increase over standing. Average. Increase over standing. A. J. 0.: 60 to 65 meters C. C. mm. mm. H. R. R.: 60 to 65 meters . . 65 to 70 meters . . T. H. H.: 60 to 65 meters . . 65 to 70 meters . . W. K.: 55 to 60 meters . . 60 to 65 meters . . 65 to 70 meters . . E. D. B.: 35 to 40 meters . 40 to 45 meters . 45 to 50 meters . 50 to 55 meters . 55 to 60 meters . 60 to 65 meters . 65 to 70 meters . 70 to 75 meters . 75 to 80 meters . 85 to 90 meters. 90 to 100 meters. J. H. G.: 50 to 55 meters . . 55 to 60 meters . . E. L. F.: 45 to 50 meters . . 50 to 55 meters . . H. M.S.: 45 to 50 meters . . 50 to 55 meters . . 104 110 100 96 75 85 84 72 74 68 77 76 95 78 82 85 94 98 98 94 100 89 93 88 11 17 4 -4 6 5 -6 -4 -10 j -2 17 4 7 16 20 -12 -16 -7 -18 1 - 4 36.90 0.01 120 3 37.03 36.84 37.18 37.13 36.90 37.12 37.25 37.28 .14 -.05 .29 .24 .01 .23 .36 .39 125 124 120 119 122 125 130 130 8 7 3 2 5 8 13 13 . ured by the kymograph tracings, was increased to not far from 3 liters per respiration or approximately three times that of the average for the other subjects. The respiration-rates in the last two days were undoubtedly abnormal, although E. L. F. reported that he was uncon- scious of making any effort and was not aware of breathing other than normally. He thought that once during the experiment his throat felt rather dry, and stated that at one time he had been troubled with asthma. PULMONARY VENTILATION DURING HORIZONTAL WALKING. The data in tables 8 to 12 show that the pulmonary ventilation for a given speed was fairly uniform, also that there was no marked change from period to period during the day. The percentage increases over the average standing rate for the various speed groups are given for EXPERIMENTS WITH HORIZONTAL WALKING. 163 E. D. B. in table 45. The average percentage changes in the ventila- tion for all of the subjects, as calculated for approximately the same speed, i. e., 52.6 to 63.2 meters per minute, are likewise given in table 45. It is apparent from these percentages that the differences between the individual subjects are very great. Even if we exclude those subjects for whom we have the least data and compare the results for W. K. and E. D. B., with whom the greatest number of experiments were made, we still find a ra,nge of from 59 to 7 1 per cent for practically the same speed of walking. The effect of the increase in speed upon the ventilation for the indi- vidual subjects can be seen from the group averages in table 44. H. R. R. shows an increase, T. H. H. shows no change, while with W. K. there was a slight increase. With E. D. B. there was practically no change for the three lower speeds; for the speeds between 56.5 and 72.2 meters per minute there was an increase over the preceding groups, but within this range the ventilation was quite constant, while above this speed the rate of increase was much greater. This is seen in table 45, in which the increase in the ventilation over the standing is figured percentagewise for this subject for the various speed-groups given in table 44. The slight difference in the percentage for the moderate speeds with the marked increase for speeds above 77.5 meters is here very apparent. TABLE 45. Percentage increase in pulmonary ventilation over standing requirement with E. D. B., at increasing speeds of horizontal walking, and for all subjects at approxi- mately the same speed (53 to 68 meters). (Values per minute.) Percentage Percentage Subjects. Average speed. increase over Subjects. Average speed. increase over standing. standing. meters. p. ct. meters. p. ct. E. D.B.... 36.2 24 A. J. O.. . 63.0 100 43.8 22 H.R.R.. . 60.9 80 46.3 26 T.H.H.. . 63.2 75 53.7 46 W. K 58.3 71 56.5 59 E. D.B.. . 56.5 59 63.9 56 J. H. G.. . 53.9 52 66.8 54 E. L. F.. . 52.6 37 72.2 53 H.M.S.. . 52.8 27 77.5 ' 67 88.5 103 96.0 122 PULSE-RATE DURING HORIZONTAL WALKING. The belief that there is a relationship between the pulse-rate and the degree of metabolism for the same subject has been expressed in previous reports from this Laboratory, 1 and for a number of years Benedict and Cathcart, Carnegie Inst. Wash. Pub. No. 187, 1913, pp. 153 and 172; Benedict and Murschhauser, Carnegie Inst. Wash. Pub. No. 231, 1915, p. 69; Harris and Benedict, Carnegie Inst. Wash. Pub. No. 279, 1919, p. 79. 164 METABOLISM DURING WALKING. it has been the practice to record carefully the pulse-rates in all the basal metabolism measurements carried out here. Such records were accordingly made in this research. The detailed data of the pulse-rates of the subjects during the hori- zontal walking periods, as obtained by the method already described, are given chronologically in tables 8 to 12. It should be stated again, however, that the difficulties which were experienced in this initial work of recording the pulse-rate have made the data incomplete. Accordingly, although the rates as reported for the individual periods are, in a large majority of cases, average values determined at three intervals about equally distributed throughout the period, nevertheless, there are individual averages which represent only one or two readings. As the pulse-rates tended to increase during the walking periods, the average value would naturally be affected by the failure to secure either the first or the last reading, and this fact undoubtedly explains some of the irregularities. Although many measurements of the pulse-rate have been made in connection with studies on muscular exercise, the difficulties of actually recording the pulse by the methods commonly used are great when the subject is exercising, and most of the records previously reported have therefore been made immediately at the end of and not during the period of exercise. 1 As the pulse-rate is subject to sudden and wide fluctuations due to mental and physical conditions, uniformity in results is perhaps more than should be expected, and only comparisons from much larger groups of results than here obtained could yield very definite conclu- sions. For this reason the speed groups in table 35 and the summary in table 44 give, perhaps, the most satisfactory method for comparing the material at hand. However, the results recorded in tables 8 to 12 show one point very clearly, namely, that the pulse-rates tended to increase as the periods continued during the forenoon. From both tables 35 and 44 it may be seen that H. R. R. had a high pulse-rate as compared with other men walking at similar speeds. With this subject the highest pulse-rate and highest metabolism were obtained on his first day of walking. (See table 8, p. 56.) The two averages for H. R. R. in tables 35 and 44 show that his pulse-rate was increased 6 beats for an average increase in speed of 6.2 meters per min- ute. T. H. H., however, shows the reverse, although the average for the heat-output increased. (See table 35.) W. K. had an increase in pulse-rate between the first and second speed-groups, but a drop of 1 beat between the second and third groups. These figures of W. K. do not cover the earlier days of his walking experiments, while the *A striking exception is that too little known but admirable research of W. P. Bowen (Bowen, A study of the pulse-rate in man as modified by muscular work. Contributions to Medical Research, dedicated to Victor Clarence Vaughan by colleagues and former students of the De- partment of Medicine and Surgery of the University of Michigan, Ann Arbor, Michigan, June, 1903, p. 462.) EXPERIMENTS WITH HORIZONTAL WALKING. 165 average speeds, as well, indeed, as the average metabolism (see table 35), are from the full quota of experiments. The relationship is but little changed, however, if the speed and metabolism averages are based on the same days for which the pulse-records are available. The variations which may occur in the pulse-rates for the same sub- ject are seen by comparing the rates of W. K. for March 17 and 25. The speed of walking on these days was almost identical and the period pulse-rates on each day were uniform, and yet there is a difference between the pulse-rates on the two days of 17 beats per minute. (See table 10, p. 58.) With E. D. B. it is seen from table 44 that with the lower speeds of the first three groups the average pulse-rate is 71 and for the next two groups with higher speed the average is 77. Omitting the group for 60 to 65 meters per minute, we find that the three speed-groups from 65 to 80 meters per minute have an average pulse-rate of 82, and the last two groups an average pulse-rate of 96. Thus, when the subject changed from the lowest average speed of 36.2 meters per minute to an average of 77.5 meters per minute, with an increase in distance walked of 41 meters per minute, the increment in the pulse-rate was but 13 beats, whereas a further increase in speed of only 19 meters per minute produced exactly the same increment in the pulse-rate, i. e., 13 beats. This marked change in rate of increase of the pulse at 80 to 85 meters per minute as a result of increase in speed is in keeping with the incre- ment found in the total heat-output for walking above this optimum speed. The high pulse-rate for the group 60 to 65 meters per minute is due to the pulse-records for January 31 and February 1, which, it will be recalled, were the first days following the return of E. D. B. from his absence on account of his lameness. In this group is one record on March 30 of a pulse-rate of 82, which is more in conformity with the pulse-rates of contiguous speed-groups, although this value is still somewhat high. With the three subjects, J. H. G., E. L. F., and H. M. S., there is a, fall in the average pulse-rate with the increase in the speed of walking. This is probably due to the fact that the sub- jects were untrained and that the lower speeds were ordinarily used on the first day, when a greater mental stimulus would naturally produce a higher pulse-rate. The fact, therefore, that these three men all showed a lowering of the pulse-rate with increase in speed is not, under the circumstances, so significant. COMPARISON OP PTJLSE-RATE DURING STANDING WITH THAT DURING HORIZONTAL WALKING. The effect upon the pulse-rate of the activity of level walking, as obtained from a comparison of these group averages with the standing average, may be seen hi table 44. With the lower speeds of W. K. and E. D. B. and in all but one instance with the three laboratory men, 166 METABOLISM DURING WALKING. J. H. G., E. L. F., and H. M. S., at similar speeds, the pulse-rate during walking was lower than in the standing periods. The difference is in many cases pronounced and implies that even with a trained subject like E. D. B. it is possible to have a lower pulse during moderate walk- ing than when standing. If, instead of using the average group values, the pulse-rates on the days when both standing and horizontal walking experiments were successively made are compared by plotting the con- Fio. 12. Typical pulse-rate curves for E. D. B. and W. K. during standing and horizontal- walking experiments. (Values per minute.) Speed of walking indicated in meters. Change of conditions shown by arrows and numbers: 1, subject sitting; 2, standing; 3, walking. Records made in the experimental periods represented by black points. Curve A, April 13; B, April 5; C, March 30; D, March 31; E, April 4, 1916; F, March 18; G, March 17, 1915. tinuous pulse-readings during the forenoon, the relationship between standing and walking values will be more clearly shown. A few curves for W. K. and E. D. B. have been plotted in figure 12. Here it is seen that whereas the pulse-rate tended to increase during the walking periods, during the standing periods there was considerable variation; also, that as a rule the increase was marked when the subject changed EXPERIMENTS WITH HORIZONTAL WALKING. 167 from standing to walking, although the reverse was sometimes true. The most striking point is the wide difference in the pulse-rate which may be expected from the same subject, even when the conditions are practically the same. It would appear as though the pulse is so sensi- tive and variable, not only from day to day, but from minute to minute, that any uniform figures are not to be expected, and even with the use of experienced and well-trained subjects the conditions of the experi- ments must be carried out with the least possible opportunity for mental disturbance during the time of the experiment. In a recent study in the Nutrition Laboratory, 1 some pulse measure- ments were made with a group of 12 normal young men, both while they were standing and while they were walking on a level at a rate of 70 meters per minute. The average standing value for this group was 79 pulse-beats per minute, while for walking the average rate varied from 88 to 85 beats between the first and twelfth minutes of walking. The standing pulse-rates of W. K. and E. D. B. are thus in keeping with this group average for standing, while the rates for walking at this speed are somewhat lower. In the case of the group of 12 men, it can not be said that the subjects were particularly trained for these experiments, though they were physically active and athletic young men. Benedict and Murschhauser 2 report that on two days their subject showed a lower pulse-rate during level walking than in the standing portion of the experiment, in spite of the fact that the metabolism was increased over 100 per cent above the basal requirements. This observation was so contrary to the general relation between the pulse- rate and the metabolism that further tests were made at the Nutrition Laboratory and similar results found. In later work 3 with a group of 5 normal men this observation was not confirmed. In a careful study of the records of W. K. and E. D. B. in the present research and the exclusion of all cases in which there might appear to be some disturbing influence which produced an unduly high pulse-rate for the standing position, we have found the instances given hi table 46 of pulse-rates that are lower during level walking at moderate speed than during the preceding time when the subject was standing. Thus, W. K., during the standing period on March 16, in three counts from 9 h 7 m a. m. to 9 h 19 111 a. m., had a pulse-rate ranging from 77.7 to 84.1 beats. The subject began walking at 10 h 45 m a. m. at a speed of 59 meters per minute. After he had walked 14 minutes, his pulse-rate was 72.7 and later 74.5. In this particular instance, the records for standing were obtained in the first period of the experiment, while those for walking were for the fourth period on that day; for the intervening Benedict, Miles, Roth, and Smith, Carnegie Inst. Wash. Pub. No. 280, 1919, p. 442. ^Benedict and Murschhauser, Carnegie Inst. Wash. Pub. No. 231, 1915, pp. 54, 55, and 85. "Benedict, Miles, Roth, and Smith, Carnegie Inst. Wash. Pub. No. 280, 1919, p. 451. 168 METABOLISM DURING WALKING. TABLE 46. Records showing decrease in pulse-rate of W. K. and E. D. B. in changing from standing position to horizontal walking in experiments without food. (Values per minute.) Subject, date, and time. Conditions, and rate of walking per minute. Pulse- rate. Subject, date, and time. Conditions, and rate of walking per minute. Pulse- rate. W. K. Mar. 16: ghQyrn g jjj 77.7 E. D. B. (Cont.) Mar. 29 (Cont.) 10 b 56 m a. m. . . Standing 86.3 12 a m Do 84.1 11 10 a.m... Walking began; 58 meters . 9 19 a m Do 81.9 1 1 40 a. m. . . Walking 83 6 in d.^ am 1 1 1 49 a. m. . . . ... Do. . 87 7 10 59 a m Walking 72.7 Mar. 30: 11 04 a m Do 74.5 10 h 51 m a. m.. . Standing 78.2 Mar 17- 11 01 a. m. . . Do 87 3 10 h 26 m a m Standing 74.8 11 10 a. m. . . Walking began ; 69 meters . 10 30 a m Do 77.2 1 1 56 a. m. . . Walking 83.4 10 34 am Do. 77.6 12 01 p. m. . . Do 82 6 10 48 a. m. . . 11 05 a m Walking began ; 67 meters . 72.8 Mar. 31: 10 h 51 m a. m. . . Standing 80 7 11 10 am Do 75.0 10 56 a. m. . . Do 77 4 11 15 am Do 76.5 11 01 a. m. . . Do 74 6 Mar. 18: 10 h 20 m a m 84.2 11 34 a. m.. . 11 55 a. m. Walking began; 55 meters . Walking 65 8 10 24 am Do 83.4 12 00 p. m. Do . . . 67 3 10 29 am Do 85.6 12 04 p. m. . . Do 70 7 10 51 a. m. . . 10 53 am Walking began; 63 meters . Walking (prelim.) 72.4 Apr. 1: 10 h 34 m a. m. . . Standing 72 4 10 58 am Do 73.6 10 39 a. m. . . Do 83 6 10 43 a. m. Do 81 E. D. B. Dec. 6.: 11 04 a.m... 11 22 a. m. . . Walking began ; 53 meters . Walking 71 3 S^o a. m. Standing (prelim.) 66.7 Apr. 3: 8 58 a. m. W^alking began ; 45 meters . 10 h 31 m a. m. . . Standing 71 8 9 23 a. m. Walking 61.6 10 35 a. m. . . Do...'. 79 2 9 33 a. m. Do. 64.4 10 40 a. m. . . Do 78 4 Jan. 31: 10 h 04 m a. m. . Standing 83.7 10 56 a. m. . . 11 16 a. m. . . Walking began; 35 meters . Walking 63 5 10 08 a.m.. . . . Do 89.7 1 1 22 a. m. . . Do 69 2 10 13 a. m. . . . . Do 90.2 11 26 a. m. . . Do 72 7 10 22 a. m. . . 10 28 a. m. . . Walking began; 62 meters . Walking (prfilirn,) ..,.,.,. 87.5 Apr. 4: 10 h 43 m a. m.. . Standing 84.8 Feb. 1 : 10 47 a. m. . Do 85 6 9 h 39 m a. m. . . Standing 93.3 11 08 a. m. . . Walking began; 36 meters . 9 45 a. m. . . Do 92.8 11 26 a. m. . . Walking 65 4 9 48 a. m. . . Do .. 93.3 11 30 a. m. . . Do 71 5 10 00 a. m. . . Walking began; 63 meters . 11 34 a.m... Do 69 2 10 03 a. m. . . Walking (prelim.) 93.4 Apr. 5: Mar. 22: lO^l^a.m... Standing 89.9 Il h 15 m a.m... Standing 72.5 10 35 a. m. . . . . Do. 89 3 11 29 a.m... Do 84.0 10 40 a. m. Do. 90 2 11 30 a.m... 11 33 a. m.. . Walking began ; 75 meters . Walking 76.5 10 57 a.m... 11 13 a.m... Walking began; 77 meters . Walking 84 9 11 37 a.m... Do 83.8 11 17 a.m... Do 85 Mar. 29: 11 23 a. m.. . Do 90 10 h 50 m a.m... Standing 80.7 10 53 a. m. . . Do 80.7 J No records for periods II and III. EXPERIMENTS WITH HORIZONTAL WALKING. 169 two periods no record was available. On March 17 the standing rate of 74.8 to 77.6 was followed by a rate of 72.8 after 17 minutes of walk- ing, which rose in 10 minutes to 76.5. A more pronounced change is seen in the records for March 18, in which case the pulse-rate after the subject had walked 7 minutes was 73.6 as compared with a standing rate of 85.6 at the end of the standing period. With E. D. B. similar cases were found. The records for February 1 have been included in the table to show that while the standing pulse was abnormally high, the pulse in the preliminary period of walking was also high, although no higher than that for standing. The rates of March 29 and 30 show that though the first walking rate was higher than the first standing rate, it was nevertheless lower than the final standing rate, even though the subject had walked 30 and 46 minutes at a speed of 58 and 69 meters per minute, respectively, between the two sets of pulse-records. It is thus evident that these records confirm the earlier observations of Benedict and Murschhauser. This fall is so pronounced as to justify the statement that a change from standing to walking at moderate speeds, i. e., 35 to 75 meters per minute, is in many instances accom- panied by a decrease in pulse-rate, although the metabolism may si- multaneously be doubled or more. In many of the records in table 46, a pulse-rate after a considerable period of forced quiescence is compared with that found early in a period of walking. It may be suggested that the change in walking was possibly agreeable to the subject and thus in part account for the apparent anomaly. This does not, however, explain such definite records as, for instance, those for E. D. B. on March 31, when all of the walking-rates were clearly lower than the standing rates. The fact that these lower rates were found after the subject had been walking in some cases from 15 to 20 minutes precludes the suggestion put forth by Benedict, Miles, Roth, and Smith 1 that possibly the low pulse-rates found by Benedict and Murschhauser had been counted during a moment of pulse-reaction from the first stimulus of walking. The fact that the pulse-rates for walking on a level at a moderate speed can be maintained at a lower rate than when the subject is standing is of prime physiological interest and warrants further study. RELATIONSHIP OF OXYGEN CONSUMPTION, PULSE-RATE, AND PULMONARY VENTILATION DURING HORIZONTAL WALKING. The relationship between the oxygen consumption and the heat-out- put of the body is so close that the oxygen consumption may, to a certain extent, be taken as a measure of the heat-output. It has also been shown by Boothby 2 that the oxygen consumption and the ven- ^enedict, Miles, Roth, and Smith, Carnegie Inat. Wash. Pub. No. 280, 1919, p. 451. 'Boothby, Am. Journ. Physiol., 1915, 37, p. 383. 170 METABOLISM DURING WALKING. tilation are linear functions, and Means and Newburgh 1 have shown that the same is true for the oxygen consumption and ventilation in relation to work. In figure 13 curves have been plotted for E. D. B. for the total heat- output, oxygen consumption, pulmonary ventilation, respiration, and pulse-rate in relation to the horizontal kilogrammeters (h. kg. m.) of work done, using the average values for the 5-meter speed-groups in table 35, page 144. These curves show how closely the heat-output and the oxygen consumption follow each other with the increasing amount of work done. They also show a constant rate of oxygen con- sumption up to the point of 2,720 h. kg. m. Above this the oxygen increases at a uniform rate with the work done, if we except the h igh point of 3,840 h. kg. m., which represents the work done for the most part in October when the experiments were begun with this subject, and he was unused to the apparatus. The curve above 4,560 h. kg. m. is somewhat more sharply ascendant than below that point, but there is no marked alteration in the oxygen consumption. P R Liter* 22 100 90 24 20 80 22 18 K> 20 16 18 14 12 10 BE KK fl .m. 2400 360O 4000 4400 4800. 5200 ), v^ais. 900 4.5 800 4.0 700 3.5 600 3.0 500 2.5 I400 2.O 6000 FIG. 13. Total heat-output (cals.), oxygen consumption (Oj), pulmonary ventilation (V), respiration-rate (R), and pulse-rate (P), of E. D. B. and W. K., referred to horizontal kilo- grammeters (h. kg. m.) for experiments with subjects walking on a level at different speeds. (Values per minute.) The supply of oxygen necessary to meet the increased needs of the body during work is determined by a number of factors, of which pul- monary ventilation and pulse are of special importance. The pulse and ventilation curves should therefore be compared in relation to the oxygen consumption. Like the curve for oxygen, the two curves for pulse-rate and ventilation show no notable changes with the smaller amounts of work. For the larger amounts the increase in the oxygen consumption is followed more closely by the pulse-curve than by the ventilation curve, as the latter does not increase, butvremains practi- cally uniform between 3,400 and 4,300 h. kg. m. This would indicate that the necessary oxygen for the increased needs of the body is met ^eans and Newburgh, Journ. Pharm. and Exp. Therapeutics, 1915, 7, p. 449. EXPERIMENTS WITH HORIZONTAL WALKING. 171 by the increase in the pulse-rate and its attendant blood-flow if that factor were known, while a ventilation of 14 liters per minute was sufficient to meet the needs during this range of increasing work. The high oxygen consumption of 633 c. c. at 3,840 h. kg. m. referred to hi the previous paragraph is accompanied by an increase ha pulse- rate, but no change is evident in the ventilation at this tune. Beyond 4,292 h. kg. m. the ventilation curve shows a marked increase, while the increase hi the pulse is less in degree, indicating that here the demand for oxygen was not met by an increase in the pulse so much as by a larger pulmonary ventilation. The respiration-rate and the volume per inspiration determine the pulmonary ventilation. A reference to the curve for the respiration-rate shows that up to 4,292 h. kg. m. the increase in the pulmonary ventilation must come from an increase in volume per inspiration rather than from any increase in the respiration-rate. Beyond 4,292 h. kg. m. the respiration-rate shows a sharp increase in keeping with the ventilation. With the data in hand, we are not able to discuss that portion of the compensation due to an increase in the oxygen-carrying power of the blood which is caused by an increase in volume of the heart-output. It is evident, however, that in a change from standing to walking there is possible an actual decrease in pulse-rate with a simultaneous increase of 100 or more per cent in the oxygen consumption. This physiological fact, even though incompletely explained at this time, yet suggests many topics for experimentation. The curves for the same factors for W. K. are also given in figure 13, and though the range in the amount of work is much less, the same characteristics are shown by his curves, namely, for the amount of work done, that the oxygen consumption and heat-output run uniformly with the increase in the horizontal kilogrammeters of work, that the ventilation shows no increase for these moderate demands, but that the increase hi the pulse-rate is responsible for the increase in the oxygen- supply. The respiration-rate for W. K., in contrast to that of E. D. B., shows an increase with a constant ventilation, indicating a change to a smaller volume per inspiration. 172 METABOLISM DURING WALKING. BODY-TEMPERATURE DURING HORIZONTAL WALKING. There were 15 days of horizontal walking on which body- temperature measurements were made with E. D. B., including hi all 41 experimen- tal periods . These walking experiments were all preceded by standing experiments in which the body-temperature was likewise measured, so that a daily comparison may be made between the standing and horizontal-walking temperatures. These two series of data, which are given in tables 6a and lla, pages 53 and 67, are summarized in table 47, in which it is seen that the average temperature during the successive walking-periods increased slightly, even though periods of rest intervened between the periods. It likewise shows that the variations in the average standing temperature were relatively slight from day to day and that the difference between the average standing temperature and the average temperature of the first walking-period shows in several cases a loss. This loss in temperature may have been TABLE 47. Summary of body-temperature measurements of E. D. B. in horizontal-walking experiments without food. Date. Distance walked per minute. Average body-temperature in successive periods of horizontal-walking experiments. Average body- temperature during standing. Increase in body- temperature due to walking. First period. Second period. Third period. Fourth period. Average. 1916 Apr. 3 meters. 35.8 36.6 51.8 54.1 56.6 60.1 63.2 63.6 66.1 75.9 77.7 77.9 88.3 92.3 97.4 C. 36-86 36.55 36.80 36.86 36.91 36.59 37.03 37.05 37.13 36.90 37.06 36.95 36.95 36.94 37.09 C. 37.12 36.73 37.02 37.14 37.00 36.78 37.20 37.21 37.17 37.00 37.23 37.09 37.28 37.29 37.46 C. 37.31 36.84 37.17 C. C. 37.10 36.71 37.00 37.00 . 36-96 36.69 37.25 37.22 37.15 36.95 37.22 37.02 37.19 37.22 37.39 C. 36-68 36.83 36.74 36.67 36.72 36.60 37.22 37.24 37.07 36.88 36.95 37.04 36.95 36.84 36.93 C. 0.42 -.12 .26 .33 .24 .09 .03 -.02 .08 .07 .37 -.02 .04 .38 .46 4 1 Mar. 31 29 20 Jan. 31 37.34 37.28 37.42 37.34 Feb. 1 Mar. 30 22 Apr. 5 37.38 10 12 37.33 37.43 37.62 11 13 Average . . . 53.1 36.91 37.18 37.30 37.38 37.07 36.89 .17 due to the removal of the blanket from around the subject, with a con- sequent increase in the loss of heat from the body-surface. (See p. 37.) It may also have been due to a change in position of the thermometer in the rectum, but the care used in inserting the thermometer to a definite depth and the frequent balancing of the leads renders this less likely. It is unfortunate that a blanket had to be used, but it was necessary to protect the subject when he was not exercising. EXPERIMENTS WITH HORIZONTAL WALKING. 173 36.80 36.60 36.40 9 c. 36.90 36.70 36.50 A ^ i /] i ^ X V r V*" *** ^ *a' Pm. o 10 oo 20 to nco a 3 4J 12B.' J 40 lOO 2C V S , \ B x f^ V* ^ ^*" 1 *J \ / r? .37METERS -u 37.20 37.00 36.80 36.60 c ^ . V t / 1 2 v^ 3 3< METER 1 J 1 */^ S , r^ 1 / 88 IETERS J r^ 1 r "% T* s^ * iHn. J O 4 10 2 b 40 ^00 Z D 12S^ *" ^ F / >j 0\ X A / 7 97 M TERS ^ N^ xl ^ r* A 7 2m. 10 2 > 11 a 5 12gm. 2 4 FIG. 14. Typical body-temperature curves for E. D. B. during periods of standing and periods of walking on a level at various speeds. 1, subject sitting; 2, standing; 3, walking on a level. Readings in experimental periods indicated by black points. Curve A, March 2; B, April 4; C, April 1; D, March 20; E, April 12; F, April 13, 1916. 174 METABOLISM DURING WALKING. The relationship between the body-temperature for standing and walking is also shown in figure 14 by 6 typical curves for different speeds of walking. Each temperature reading is indicated, those within the experimental periods being represented by black points and those in the intervals between the experimental periods by small circles. The changes to standing, walking, or sitting are shown by arrows, with accompanying index numbers, and the rate of walking is given in each instance. Curve A, for comparison, records sitting and stand- ing values only. Nearly every individual period in each curve shows an increase in the temperature during the period with both standing and walking. There is usually a disturbance in the temperature at the points indicated by arrows when the subject changed his position, which is possibly due to a change in position of the thermometer. The curve of April 4 (B) is in- serted especially to show the marked variation in temperature which was experienced when the subject stood (2) at 10 h 30 a. m. before the third period and again when he began walking (3) at ll h 6 m a. m. before the fourth period. It is possible that the depression in temperature before the fourth period may have been due to removal of the blanket, though no note regarding it appears in the records. In both these instances the temperature fell for at least 10 minutes, after which it became settled and subsequently rose as usual. This displacement of the temperature level results in an average walking temperature which is less than the average standing temperature, but it is seen that the increase during the walking-periods was of about the same order as on the other days. The increase in temperature with the transition from standing to walking does not manifest itself immediately for the moderate speeds (see curves B, C, and D for April 4, April 1, and March 20), there being apparently a lag of from 6 to 10 minutes before the rise appears. This lag is, however, somewhat shortened in curves E and F (April 12 and 13), with speeds of 88 and 97 meters. These latter curves show a much more rapid rise in temperature in each period, with a tendency to reach a maximum, particularly in curve E. The fact that the blanket was removed at the time that the walking began is undoubtedly a factor here in preventing as quick a response as there would have been had the subject stood and walked under exactly the same conditions of clothing. The increase in temperature is almost always larger for the first walking-periods than for the subsequent periods, showing that the difference between the rate of heat-production and radiation was becoming constantly less and that a more or less constant temperature would have been attained had the period been sufficiently prolonged. The effect of speed of walking upon the temperature curves is not marked, except at the higher rates. The general character of the curves in figure 14 and others not presented indicate but little difference EXPERIMENTS WITH HORIZONTAL WALKING. 175 at the different speeds. Apparently the exercise of walking at the normal speeds used for the most part in this research was not sufficient to produce any marked changes in body-temperature. Referring again to table 47, in which it has been necessary to compare only the average temperatures, it is seen that although the highest absolute temperature and largest increases over the standing values are with the highest speeds, the lowest speed also has a high average temperature as well as large increase, and that the increases over the standing temperatures are irregular. The average walking temperature would depend upon the duration of walking as well as upon the speed. Consequently, no definite statement as to the influence of speed can be made other than that, in the intermittent periods here conducted, the maximum in- crease for any speed below 100 meters per minute did not exceed 0.5 C., and that for moderate speeds the temperature increase would probably be not far from 0.25 C. BLOOD-PRESSURE DURING HORIZONTAL WALKING. The increase in the supply of oxygen to the tissues with increased demand due to exercise is dependent upon a chain of processes. The increase in pulmonary ventilation and pulse-rate, the change in the dis- tribution of the blood-flow to those muscles more in need of oxygen, and the general increase in the blood-flow itself, all contribute to the imme- diate supply of oxygen. The increase in the blood-flow is one of the largest, if not the largest, factor in maintaining this addition to the oxygen-supply, and Krogh and Lindhard 1 have shown that during work the blood-flow may be eight times that during rest. This increase in blood-flow is, at least above certain limits, accompanied by an in- crease in blood-pressure. It thus becomes of interest to record the blood- pressure during periods of exercise, and this was done with E. D. B. for both the standing and walking experiments overaperiod of several weeks. During this time there were 13 days on which records of the blood-pres- sure were made for both standing and horizontal-walking periods. These horizontal-walking values are recorded in table 1 la (p. 67) . It should be recalled that they were taken just prior to and immediately following the periods of walking proper, as it was not possible to read the pres- sure during the act of walking. (See p. 37.) Cotton, Rapport, and Lewis 2 have recently shown that the blood-pressure immediately on the cessation of exercise indicates little or no increase above the rest- ing value, but within 10 seconds it begins to increase and continues to rise for a period of 30 to 60 seconds, after which it again tends to fall to normal value. While it is possible that the readings as reported by us may not have occurred at the point of maximum pressure following walking, it is quite certain that the readings were close to it and beyond and Lindhard, Skand. Arch. f. Physiol., 1912, 27, p. 100. 'Cotton, Rapport, and Lewis, Heart, 1917, 6, p. 269. 176 METABOLISM DURING WALKING. the point of minimum value at 10 seconds. Although the readings can not be said to be the blood-pressures during horizontal walking, it is believed that they approach closely to them, and as the conditions under which the readings were made were alike, the results are com- parable. Disregarding the fact that there was some variation in the speed of walking for the periods on the same day, it is seen in table lla that the blood-pressure shows but little tendency to change from period to period on the same day, the difference being 2 mm., with an extreme of 4 mm. on two occasions. For a comparison between the average standing and the average walking blood-pressures on the same date, a summary is presented in table 48. The blood-pressure for the first walking-periods is here seen to be 5 to 16 mm. higher than the average standing values for the same day. The average increase is 9 mm. TABLE 48. Summary of bloods-pressure records for E. D. B. in horizontal-walking experi- ments without food. Date. Distance walked per minute. Average blood-pressure in successive periods of horizontal-walking ex- periments. Average blood- pressure during standing. Increase in blood- pressure due to walking. First period. Second period. Third period. Average. 1916. Apr. 3 meters. 35.8 36.6 51.8 54.1 56.6 60.1 66.1 75.9 77.7 77.9 88.3 92.3 97.4 mm. 124 117 124 124 124 122 119 122 123 129 130 130 131 mm. 123 118 125 127 125 123 117 118 127 129 129 129 131 mm. 121 118 123 mm. 123 118 124 126 ' 125 123 118 120 125 129 130 129 131 mm. 116 113 115 120 109 114 113 110 118 121 118 118 117 mm. 7 5 9 6 16 9 5 10 7 8 12 11 14 4 1 Mar. 31 29 20 30 22 Apr. 5 125 10 12 130 129 131 11 13 Average .... 67.0 125 125 125 125 116 9 The degree of increase over the standing does not show an evident connection with the speed, nor does the speed of walking show a uni- form effect upon the absolute blood-pressure readings until the rate of 88.3 meters per minute is reached. At this point the blood-pressure is noticeably higher than for the more moderate speeds. The average blood-pressure for the horizontal-walking experiments on the days when the speed was 75.9 meters per minute or below was 122 mm., and ranged from 118 to 126 mm. Above 75.9 meters per minute it was 129 mm., ranging from 125 to 131 mm. PHYSIOLOGY OF MOUTH-BREATHING APPLIANCES. 177 The effect of horizontal walking upon the blood-pressure is there- fore not large, even at the highest speeds here reported, as compared with the increases in blood-pressures known to occur with other forms of work, such as those found in exercise with dumb-bells by Cotton, Rapport, and Lewis. 1 There is, however, a point above 80 meters per minute at which the effect upon the blood-pressure of the speed of walking may be clearly noted. EXPERIMENTS WITH GRADE WALKING. As explained in the section on methods (p. 29), the treadmill was constructed with two long screw members attached to the head, by means of which the front of the treadmill could be raised so as to give angles of elevation as desired up to approximately 45. Aside from the fact that under these conditions the subject walked on a pre- determined incline, the details of the grade-walking experiments were in no respect different from those with horizontal walking. As the degree of elevation increased, less power was needed to drive the tread- mill, and at the highest grades the weight of the subject alone would have been sufficient to cause the speed to increase continuously. To control this and thus secure uniformity in speed, an adjustable brake was placed on the shaft of the motor. (See p. 29 and fig. 1, p. 19.) This tendency to an increase in speed during the experiment was a frequent source of trouble, and careful attention was required to pre- vent any gradual alteration in speed from unexpectedly developing. The results of the measurements in the grade-walking experiments are given hi detail in tables 13 to 16a (pp. 69 to 89), in which the values are chronologically arranged for all of the experimental periods with every subject. Before discussing the results of these experiments, a consideration of the method used for studying the respiratory exchange is desirable, more especially the use of the mouthpiece under the special conditions of grade walking. PHYSIOLOGY or MOUTH-BREATHING APPLIANCES. While the mouthpiece in its various forms has been extensively used for respiration experiments with the subject lying or standing or walk- ing, there has been much criticism by investigators as to the physio- logical effects of using such an appliance. Some go so far as to state that it is physiologically impossible for a man to breathe normally through a mouthpiece. This extreme opinion is held by only a few workers on the respiratory exchange. With walking experiments, however, the question might fairly be raised whether the use of the mouthpiece would affect the results obtained, more especially during the severe exercise of grade walking, when the oxygen consumption would necessarily be very considerable and the pulmonary ventila- , Rapport, and Lewis, Heart, 1917, 6, p. 269. 178 METABOLISM DURING WALKING. tion especially large. Is the resistance, for example, too great? Of special interest is the fact that much of this report deals with the physiology of respiration during the period of transition from standing to walking, and the reverse from walking to standing. If breathing through a mouthpiece is abnormal, the value of these studies of transi- tion would be lessened. In the ordinary technique the mouthpiece is usually inserted about two minutes before the actual experiment begins. To test the question as to whether this preliminary period of breathing through the mouth- piece was sufficiently long for the subject to adjust himself to the new conditions, a number of experiments were carried out in which the mouthpiece was inserted 15 or more minutes before the actual beginning of the experiment, and a comparison series of experiments was made in which the mouthpiece was inserted almost immediately, i. e., a few seconds before the period began. These experiments were all with E. D. B. between March 2 and 8, 1916, inclusive. On two of the days the subject stood; on four of the days he walked on a 30 per cent incline at a rate of approximately 50 meters per minute. The standing or walking was continuous on every day throughout each set of two com- parison periods, and at the end the subject sat down and rested. In the first period in each pair the subject breathed through the mouth- piece on an average of 15 minutes before the period began. The actual period for the measurement of the metabolism varied from 7 minutes and 24 seconds to 10 minutes and 52 seconds, averaging not far from 9 minutes. There was then an interval which was usually 10 to 12 minutes long. On March 4 the first interval was 20 minutes and on March 7 the interval, owing to some trouble with the apparatus, was 50 minutes. On both these days walking experiments were made, and the subject walked continuously even in these intervals. In the second period hi the comparison the mouthpiece was not in- serted until just before the beginning of the test, so that usually the period began on the second respiration, with an interval between the insertion of the mouthpiece and the beginning of the metabolism measurements of never more than 15 seconds. Since this procedure was carried out in both the standing and walking comparisons, it would seem as if the influence of mouthpiece breathing upon the metab- olism and physiological factors should be demonstrated by such a series of tests. EFFECT OF MOUTHPIECE BREATHING UPON METABOLISM. Although the data for these comparison tests are incorporated in the statistical tables 6 and 16, they are also summarized here in table 49. In the first test, namely, March 2, 1916, the influence on the metabolism of the time of insertion of the mouthpiece was studied only with the subject standing, and three comparisons were made. On March 3 the PHYSIOLOGY OF MOUTH-BREATHING APPLIANCES. 179 TABLE 49. Respiratory exchange of E. D. B. in experiments without food for studying effect of long and short duration of preliminary mouthpiece breathing. 1 ( Values per minute.) Date, No. of comparison, and conditions of experiment. Work due to grade-lift. 2 Carbon dioxide. Oxygen. Respiratory quotient. After 15 minutes prelimi- nary mouth- piece breath- ing. After 15 seconds prelimi- nary mouth- piece breath- ing. After 15 minutes prelimi- nary mouth- piece breath- ing. After 15 seconds prelimi- nary mouth- piece breath- ing. After 15 minutes prelimi- nary mouth- piece breath- ing. After 15 seconds prelimi- nary mouth- piece breath- ing. After 15 min utes prelimi- nary mouth- piece breath- ing. After 15 seconds prelimi- nary mouth- piece breath- ing. Standing. Mar. 2: First kg. m. . kg. m. c. c. 202 198 185 c. c. 192 187 192 c. c. 236 244 ( J ) c. c. 239 229 (243) 0.86 .81 (') 0.81 .82 .79 Second Third Average . . . 195 190 240 234 .83 .81 Mar. 3: First 186 197 185 194 191 186 240 241 233 244 246 241 .78 .82 .79 .80 .78 .77 Second Third Average. . . 189 190 238 243 .80 .79 Grade walking. 4 Mar. 4 : First 898.5 863.8 889.4 898.5 1,621 1,552 1,624 1,625 1,764 1,751 1,829 1,914 .92 .89 .89 .86 Second Average . . . Mar. 6: First 881.2 894.0 1,587 1,625 1,758 1,872 .91 .87 933.6 959.2 953.7 968.3 1,763 1,800 1,783 1,795 1,923 2,044 2,013 2,015 .92 .88 .80 .89 Second Average . . . Mar. 7: First 946.4 961.0 1,782 1,789 1,984 2,014 .90 .89 925.7 927.5 1,774 1,682 1,909 1,942 .93 .87 Mar. 8: First 924.7 926.5 930.1 924.7 944.5 933.7 1,761 1,807 1,769 1,735 1,766 1,723 1,891 1,961 2,011 1,942 2,073 2,043 .93 .92 .88 .89 .85 .84 Second Third Average . . . 927.1 934.3 1,779 1,741 1,954 2,019 .91 .86 J The subject stood continuously or walked continuously in each comparison, i. e., also in the interval between the two tests. Between the comparisons he sat down and rested for approxi- mately 30 to 40 minutes. The time given for the preliminary mouthpiece breathing is approxi- mate. 2 See table 55, column/, p. 209. 'Measurement of oxygen could not be obtained in this period. 4 In the grade-walking experiments, the grade was 30 p. ct. and the speed averaged 49 meters on March 4, 51 meters on March 6, and 52 meters on March 7 and 8. 180 METABOLISM DURING WALKING. series was duplicated under the same conditions. Considering average values only, it can be seen that the carbon dioxide on the first day was slightly larger when the mouthpiece was inserted 15 minutes before the test, but on the second day it was practically the same with both periods of preliminary breathing. The oxygen consumption was somewhat higher on the first day and correspondingly lower on the second day with the long preliminary breathing. The respiratory quotient was slightly higher in both series of tests with the longer preliminary breathing. The evidence as a whole can not be said, however, to indicate that with this subject standing there is an appreciable differ- ence in the effect upon the measured metabolism as to whether the mouthpiece is inserted 15 minutes before the period begins or imme- diately before. On four days walking experiments were made, and while there was every effort to secure exactly the same rate of walking, unfortunately this could not be maintained. Slight differences in the total amount of work performed accordingly appear. While the rate of walking was approximately 50 meters per minute, a little less than 2 miles an hour, it actually varied in the different periods on these days from 47.2 to 53.0 meters per minute. Usually the rate of walking was slightly greater with the second test in the comparison, namely, that with the short preliminary breathing, the difference averaging not far from 1 per cent. These differences are important to take into consideration in the analysis of the results. Of the two factors, carbon dioxide and oxygen, one would naturally expect that an abnormality in respiration due to the mouthpiece would produce more immediate fluctuations in the amount of carbon dioxide exhaled. This may be owing to a local "pumping-out" effect, and consequently it is not surprising that the values for carbon dioxide do not show regularity. On the first two days with grade walking these values are somewhat higher, and on the last two days measurably lower with the short preliminary breathing period. Since, as stated above, when there was a difference in the rate of walking, it was almost invariably more rapid in the second test of the comparison, it can be seen that there is no relationship between the carbon dioxide and the slightly higher rate of walking, nor indeed any relationship with the use of the mouthpiece, and the differences in amounts simply illustrate the variability in the carbon-dioxide excretion that one may expect to find under the conditions of a test Iik9 this. A truer measure of the metabolism is the oxygen consumption, and we find here that on all four days the oxygen consumption was slightly higher in the period with the short preliminary breathing. This is almost always in full accord with the slight differences in the rate of walking, and can therefore be readily explained by an increase in the oxygen consumption necessitated by an increase in the rate of walking. PHYSIOLOGY OF MOUTH-BREATHING APPLIANCES. 181 That it is not wholly explained by this is shown by the fact that the average increase in the rate of walking with the short preliminary breathing period is only about 1 per cent as compared with the actual increment of 2 per cent in the oxygen consumption. The evidence is therefore to the effect that with but 15 seconds of preliminary mouth- piece breathing, a slightly greater oxygen consumption is required during the experimental period than with 15 minutes of preliminary breathing through the mouthpiece. The respiratory quotient on the four days is invariably lower with the short period of preliminary breathing. At tunes the difference is very considerable, even as large as 0.06. It is therefore clear that the mouthpiece breathing is not ideally adapted for an analysis of the character of the combustion when heavy work is being performed. A large number of experiments have been made in the Nutrition Labo- ratory on the comparison of various types of respiration apparatus, using mouthpieces, nosepieces, and masks, and these show that for periods of rest no appreciable difference exists between the various types employed. 1 The true respiratory quotient obtained in these walking experiments is difficult to valuate. A priori, one could take the ground that the longer the mouthpiece was inserted in the mouth, the more normal the respiration would be. But in any event the percentage error is small, probably not over 2 per cent, and the measure- ments of the metabolism under conditions of great physical activity, such as obtained in many of the experiments reported in this book, can hardly be much, if any, inside of this limit of accuracy. The natural conclusion is, therefore, that although practically all of the experiments were made with a short period of preliminary mouthpiece breathing, rather than a 15-minute period of preliminary breathing, and these tests indicate that the metabolism is thereby slightly increased if measured by the oxygen consumption, yet it does not seem advisable to attempt a correction of the results for the small differences shown in this series of tests. As previously stated, in actual experiments the mouthpiece is usually inserted about 2 minutes before the observations of the metabolism begin. This preliminary period is measurably greater than the short period in the series of comparison tests, but much shorter than the 15-minute periods. Doubtless the error due to the insertion of the mouthpiece is not distributed in a straight line, and it is more than reasonable to suppose that at the end of 2 minutes the oxygen con- sumption is more nearly in accord with that obtained with the longer period of preliminary respiration than with that with the very short period. Carpenter, Carnegie Inst. Wash. Pub. No. 216, 1915. Also, Hendry, Carpenter, and Emmes, Boston Med. and Surg. Journ., 1919, 181, pp. 285, 334, and 368. 182 METABOLISM DURING WALKING. EFFECT OF MOUTHPIECE BREATHING UPON RESPIRATION-RATE, PULMONARY VENTILATION, AND RATE OF OXYGEN CONSUMPTION. The effect upon the respiration-rate and the pulmonary ventilation of long-continued preliminary breathing through the mouthpiece was also studied in these experiments, for it was conceivable that the mouth- piece and nose-clip might cause a change in the ventilation which would result hi a pumping-out of carbon dioxide and a consequent change in the respiratory quotient and the computed heat. As previously stated, hi ordinary experimenting it has been the practice to insert the mouthpiece 2 or more minutes before the beginning of the period. If there were any alteration in the respiration-rate and volume of venti- lation under these conditions, it ought to be apparent in experiments made with such wide variations in the length of preliminary breathing as comparison periods of 15 seconds and 15 minutes would give. If this variation in conditions resulted in no material difference, it is safe to say that the usual 2-minute period of preliminary breathing through the mouthpiece was sufficient to insure uniformity. The respiration-rate and pulmonary ventilation were determined in 1-minute and )^-immite intervals during the first 5 to 7 minutes of the period by counting the respirations and measuring their excursion on the kymograph, the time-intervals being marked in minutes by means of a signal magnet in contact with a clock. The ventilation as thus measured is the apparent ventilation, and the data have not been cor- rected for temperature changes. At the time that these measurements of the ventilation were made, advantage was taken of the opportunity to measure the rate of the oxygen consumption during the first few minutes of the period. This was done by the use of the double spirometer (see fig. 2, p. 22), and the measurement of the kymograph record. During the regular experi- ments it was the practice to admit the oxygen at such a rate as to equalize the consumption, but in determining the rate in the mouth- piece comparison experiments, no oxygen was admitted until the spirometer-bell had reached a low level. The main spirometer was then refilled from the duplicate spirometer by the method described on page 21. Under these conditions, instead of a gradual alteration in the relative positions of the kymograph tracings as a result of the contractions in the volume of the ventilating circuit, the kymo- graph record showed a slight rise with each respiration and a sud- den fall when new oxygen was finally admitted from the duplicate spirometer. By measuring the rise in the kymograph record due to the fall of the spirometer-bell in a specified period of time, the rate of oxygen consumption could be estimated for succeeding fractions of a minute. There is a valid criticism against this method of measurement, for it assumes that the subject exhales to the same point of deflation of the PHYSIOLOGY OF MOUTH-BREATHING APPLIANCES. 183 lungs each time and that the residual volume in the lungs and the temperature conditions remain constant. Any alteration in the resid- ual volume would alter the base of the respiration tracings on the kymograph. This, of course, does occur occasionally in a deep inhala- tion, but the low points of the tracings which mark the limits of expira- tion are remarkably uniform after the first few respirations of the period, and the rate at which these points rise give a very fair index of the rate of oxygen consumption. The method, however, is intended merely as an approximate comparison, for the volumes thus read are apparent volumes and, like those for the pulmonary ventilation, are uncorrected for temperature changes. The lower record (A) in figure 15 is the reproduction of a kymograph tracing when the subject was standing and shows the rise in the curve as the oxygen was absorbed from the ventilating circuit, without re- newal. The upper record (B) in the same figure was obtained with the subject walking, and indicates the points at which the main spirom- eter was refilled from the duplicate spirometer. -I r -i i i- -f -I) Ih FIG. 15. Reproduction of kymograph records in mouthpiece experiments, with intermittent renewal of oxygen. A, subject standing without introduction of oxygen. B, subject walking on a 30 per cent grade, 50 meters per minute; intermittent renewal of oxygen. Time and pulmonary ventilation indicated by the horizontal tracings. 184 METABOLISM DURING WALKING. EFFECT WITH SUBJECT STANDING. In table 50 the data for the respiration and ventilation rates ob- tained with the subject standing are given for E. D. B. for March 2 and 3, 1916. In the first test in each comparison the subject had been standing with the mouthpiece inserted for at least 15 minutes previous to the beginning of the measurements. In this test the values were measured in minute intervals. In the second test of each comparison the mouthpiece was inserted but a few seconds before the measurements began. The measurements were made in quarter minutes and the per minute rate calculated from the results. These quarter-minute rates are also averaged for comparison with the measurement for the cor- responding full minute in the preceding test, when the mouthpiece was inserted 15 minutes. Three comparisons were obtained with the subject standing on both March 2 and 3, with intervals of rest of 30 minutes or more between the first and second and the second and third comparisons. The respiration-rate in the periods when the mouthpiece had been used for approximately 15 minutes does not, on the whole, appear to be different from the rate when the mouthpiece was inserted immediately before the experiment. There seems to be a slight tendency for the respira- tion-rate to increase with the time, but this is as apparent with the long preliminary breathing as with the short. In most cases, when the pulmonary ventilation was calculated on the quarter-minute basis, a slightly larger ventilation was found for the first quarter-minute during the periods when the mouthpiece had been but briefly inserted. There are, however, several exceptions to this. No greater variation was found under one condition than under the other, if we take the per minute averages for" comparison. With the exception of a slight disturbance for the first one-quarter minute, it appears that the ventilation was as constant under one condition as under the other, and that both the respiration and ventilation with the subject standing were unaffected by the presence of the mouthpiece during a short or a long preliminary breathing. The oxygen consumption per minute for the first 7 or 8 minutes of each period was computed as outlined on page 182. Considerable varia- tions actually occur hi single minutes, the range being, with the subject standing, from 186 to 418 c. c. per minute. Little, if any, regularity can be observed on any day, although it is worthy of note that both the extreme values occurred in the first minute. The inherent errors hi the method of measurement outlined above make its use questionable when such small per minute amounts of oxygen were obtained, and hence we do not tabulate them. EFFECT DURING GRADE WALKING. On March 4, 6, 7, and 8, the usual grade-walking experiments were varied to the extent that in each alternate period the subject breathed PHYSIOLOGY OF MOUTH-BREATHING APPLIANCES. 185 TABLE 50. Respiration-rate and rate of pulmonary ventilation (unreduced) in experiments without food, for studying effect of long and short duration of preliminary mouthpiece breathing. Subject, E. D. B., standing. (Values per minute.) Date and interval measured. First comparison. Second comparison. Third comparison. After 15 minutes preliminary mouthpiece breathing. After 15 seconds preliminary mouthpiece breathing. After 15 minutes preliminary mouthpiece breathing. After 15 seconds preliminary mouthpiece breathing. After 15 minutes preliminary mouthpiece breathing. After 15 seconds preliminary mouthpiece breathing. Respi- ration- rate (full min- utes) . Rate of pul- monary venti- lation unre- duced (full min- utes). Respi- ration- rate (X min.). Rate of pul- monary venti- lation, unre- duced (X min.). Respi- ration- rate (full min- utes) . Rate of pul- monary venti- lation unre- duced (full min- utes). Respi- ration- rate (X min.). Rate of pul- monary venti- lation, unre- duced (K min.). Respi- ration- rate (full min- utes) . Rate of pul- monary venti- lation unre- duced (full min- utes). Respi- ration- rate (Y* min.). Rate of pul- monary venti- lation, unre- duced (X min.). 1916. Mar. 2: 1st min 2d min 15.1 14.6 15.5 15.2 16.8 16.5 liters. 9.5 9.9 10.3 10.4 11.1 15.2 14.3 15.0 15.5 liters. 11.2 10.2 10.3 9.0 15.9 13.8 13.9 16.3 15.1 liters. 10.6 9.3 9.0 10.6 10.1 12.9 13.1 12.9 16.2 liters. 9.2 9.3 9.0 8.5 16.0 15.0 15.7 16.5 16.6 liters. 9.6 9.6 10.4 10.2 10.6 16.6 15.5 15.2 15.2 liters. 11.6 11.1 9.6 10.5 15.0 10.2 13.8 9.0 15.6 10.7 16.6 16.0 16.7 14.5 9.3 10.1 11.2 8.9 15.1 16.3 15.5 16.6 8.0 9.8 11.1 10.6 15.7 15.2 15.7 16.3 9.9 9.9 9.9 9.6 16.0 9.9 15.9 9.9 15.7 9.8 3d min 15.1 16.7 16.1 16.1 9.8 10.6 10.0 9.8 15.2 15.1 15.1 16.0 10.9 10.0 10.1 10.8 15.2 14.0 15.7 15.7 9.8 9.7 10.8 11.2 16.0 10.1 15.4 10.5 15.2 10.4 4th min 16.5 17.2 19.4 17.0 10.6 11.3 13.1 11.0 16.5 15.5 15.1 16.6 10.3 9.5 8.8 10.5 15.7 15.6 16.1 15.1 9.8 9.9 11.4 10.8 17.5 11.5 15.9 9.8 15.6 10.4 5th min .... 6th min .... 16.5 15.5 16.6 16.2 10.8 11.0 11.6 9.4 16.5 16.5 16.5 17.0 11.6 10.5 10.5 10.0 14.6 14.7 17.4 15.8 9.6 9.3 11.1 11.1 16.2 10.7 16.6 10.6 15.6 10.3 10.6 16.2 16.6 9.3 10.8 15.8 16.9 10.4 10.7 186 METABOLISM DURING WALKING. TABLE 50 Respiration-rate and rate of pulmonary ventilation (unreduced) in experiments without food, for studying effect of long and short duration of preliminary mouthpiece breathing. Subject, E. D. B., standing. (Values per minute.) Continued. Date and interval measured. First comparison. Second comparison. Third comparison. After 15 minutes preliminary mouthpiece breathing. After 15 seconds preliminary mouthpiece breathing. After 15 minutes preliminary mouthpiece breathing. After 15 seconds preliminary mouthpiece breathing. After 15 minutes preliminary mouthpiece breathing. After 15 seconds preliminary mouthpiece breathing. Respi- ration- rate (full min- utes). Rate of pul- monary venti- lation unre- duced (full min- utes). Respi- ration- rate (# min.). Rate of pul- monary venti- lation, unre- duced (X min.). Respi- ration- rate (full min- utes) . Rate of pul- monary venti- lation unre- duced (full min- utes) . Respi- ration- rate (y< min.). Rate of pul- monary venti- lation, unre- duced (X min.). Respi- ration- rate (full min- utes) . Rate of pul- monary venti- lation unre- duced (full min- utes) . Respi- ration- rate (X min.). Rate of pul- monary venti- lation, unre- duced (X min.). 1916. Mar. 3: 1st min J 14.2 *14.2 15.3 14.2 15.1 16.7 liters. 9.4 9.4 9.5 9.1 9.9 10.7 15.7 15.3 14.8 14.9 liters. 11.1 10.4 9.8 10.2 15.4 14.5 16.0 17.4 17.1 liters. 10.7 9.7 10.6 11.1 11.1 11.0 15.0 15.5 15.9 14.4 liters. 11.3 9.0 9.8 9.4 15.6 15.3 16.1 16.3 16.7 liters. 10.0 9.7 10.6 10.5 10.7 13.9 14.1 16.1 15.2 liters. 9.8 8.7 10.4 9.9 15.2 10.4 15.2 9.9 14.8 9.7 2d min 14.3 14.2 16.1 16.1 9.3 8.2 10.4 10.7 13.7 15.0 16.6 16.0 8.1 8.8 10.7 10.5 15.7 16.2 15.8 16.2 9.6 10.2 9.7 10.3 15.2 9.6 15.3 9.5 16.0 9.9 3d min .... 4th min . . . 5th min . . . 6th min . . . 16.1 15.7 15.9 17.0 10.6 9.3 11.1 11.6 15.4 15.5 15.8 14.2 9.9 9.8 9.8 8.5 16.2 16.6 15.7 15.7 10.3 10.7 10.4 10.0 16.2 10.6 15.2 9.5 16.1 10.4 17.0 16.0 16.5 17.0 11.0 10.0 10.2 10.8 15.8 16.7 17.8 18.1 10.4 11.3 11.9 11.6 15.7 15.8 16.7 15.2 10.2 9.5 10.1 10.0 16.6 10.5 17.1 11.3 15.9 9.9 16.7 14.0 15.7 16.7 11.0 9.9 9.8 11.5 18.2 16.7 15.8 16.6 11.9 11.3 10.7 10.9 16.2 16.9 16.6 16.6 10.1 11.6 11.6 11.0 15.8 10.6 16.8 11.2 16.6 11.1 16.7 16.7 16.9 12.2 11.5 11.5 17.2 17.6 16.6 16.8 11.3 10.7 10.2 15.7 10.1 1 Average of the first two full minutes. PHYSIOLOGY OF MOUTH-BREATHING APPLIANCES. 187 through the mouthpiece for approximately 15 minutes before the period began and from 10 to 15 seconds for the other periods, the procedure being similar to that in the standing tests. In these experiments the oxygen consumption was large and hence the respiration-rate and pulmonary ventilation were correspondingly large. The error in the technique would consequently play a much smaller r61e than in the standing experiments. Table 51 gives the respiration and ventilation rates on these days measured in minute or quarter-minute intervals for the first 5 to 7 minutes of the period. 1 The method of presentation of results is the same as in table 50. The results show that the respiration-rate underwent no pronounced change in one direction or the other in those periods in which the sub- ject had been breathing through the mouthpiece for 15 minutes and in which the measurements were made on the per minute basis. There was a slight tendency for the rate to be usually a little lower than with the short preliminary use of the mouthpiece. In the quarter-minute measurements there was more variation, which was sufficiently small to be ascribable to the error hi estimation for such short periods as one-quarter minute, and this variation was not so uniform as to indi- cate that the mouthpiece had more than a temporary effect. It would appear, therefore, that the practice in our experiments of inserting the mouthpiece 2 minutes before the period began probably gave ample tune for the respiration-rate to become settled, even under conditions requiring a great increase in the rate of respiration. The pulmonary ventilation hi the grade-walking experiments varied considerably from minute to minute. The volumes per minute were usually larger in those periods hi which the mouthpiece had just been inserted than in the periods in which it had been used for 15 minutes or more, but this difference tends to become smaller as the experiment pro- gressed. It may also be noted that the ventilation for these periods was frequently larger in the first and second quarter-minutes than in the next following, indicating a rather rapid adjustment to the dis- turbance of the mouthpiece at the beginning of the period. From the data in table 51, which usually represent only 5 or 6 min- utes of an 8 to 11 minute period, the general impression is obtained that in the majority of periods the unreduced pulmonary ventilation was somewhat higher in those tests with a short period of preliminary mouthpiece breathing. This impression is confirmed by the average values of the reduced ventilation for the whole of each period given in table 16 (p. 78) for the several dates. Bearing in mind that the comparison periods were alternate, and that the first measurement on each day was preceded by a long period of mouthpiece breathing, it is seen that the pulmonary ventilation was in all but two sets of com- parisons (that of March 7 and the last pan* of March 8) larger in the period with the short preliminary mouthpiece breathing. Averaging 1 The quarter-minute records were computed to the full-minute basis. 188 METABOLISM DURING WALKING. TABLE 51. Respiration-rate and rate of pulmonary ventilation (unreduced) in grade-walking experiments without food, for studying effect- of long and short duration of preliminary mouthpiece breathing. Subject, E. D. B., SO per cent grade, at approximately 50 meters. (Values per minute.) Date, and interval measured. First comparison. Second comparison. Third comparison. After 15 minutes preliminary mouthpiece breathing. After 15 seconds preliminary mouthpiece breathing. After 15 minutes preliminary mouthpiece breathing. After 15 seconds preliminary mouthpiece breathing. After 15 minutes preliminary mouthpiece breathing. After 15 seconds preliminary mouthpiece breathing. Respi- ration- rate (full min- utes). Rate of pul- monary venti- lation unre- duced (full min- utes). Respi- ration- rate (X min.). Rate of pul- monary venti- lation, unre- duced (tf min.). Respi- ration- rate (full min- utes). Rate of pul- monary venti- lation unre- duced (full min- utes). Respi- ration- rate M min.). Rate of pul- monary venti- lation, unre- duced (X min.). Respi- ration- rate (full min- utes) . Rate of pul- monary venti- lation unre- duced (full min- utes). Respi- ration- rate (X min.). Rate of pul- monary venti- lation, unre- duced (X min.). 1916. Mar. 4 27.0 28.0 27.5 29.0 27.4 liters. 47.0 47.9 49.4 48.8 48.5 27.8 27.6 29.8 28.8 liters. 51.7 47.4 46.2 52.6 29.0 29.3 30.0 30.2 29.8 30.0 29.0 liters. 45.0 47.1 48.4 49.2 49.0 48.9 50.0 26.7 28.0 26.7 27.3 52.1 50.3 46.4 47.5 liters. liters. 1st min 2d min 28.5 49.5 27.2 49.1 31.4 30.3 28.8 31.7 55.1 44.7 48.8 53.5 29.5 28.4 32.0 26.0 49.5 50.7 52.6 47.0 30.6 50.5 29.0 50.0 3d min 32.2 30.0 31.0 32.0 53.2 49.6 54.2 57.4 27.3 28.0 28.0 25.8 52.3 49.5 50.3 49.8 31.3 53.6 27.3 50.5 4th min .... 5th min. . . . 6th min 30.3 36.3 32.8 30.8 52.6 52.4 48.3 47.0 30.6 28.0 28.0 24.0 49.5 45.7 51.1 44.9 32.6 50.1 27.7 47.8 29.9 50.8 22.1 37.5 Mar. 6: 1st min 29.3 50.5 28.5 30.0 29.5 29.7 57.1 56.2 54.1 54.8 28.6 31.3 30.7 31.3 56.2 55.6 54.2 56.1 29.4 55.6 30.5 55.5 PHYSIOLOGY OF MOUTH-BREATHING APPLIANCES. 189 'ABLE 51. Respiration-rale and rate of pulmonary ventilation (unreduced) in grade-walking experiments without food, for studying effect of long and short duration of preliminary mouthpiece breathing. Subject, E. D. B., 30 per cent grade, at approximately 50 meters. (Values per minute.) Continued. Date and interval measured. First comparison. Second comparison. Third comparison. After 15 minutes preliminary mouthpiece breathing. After 15 seconds preliminary mouthpiece breathing. After 15 minutes preliminary mouthpiece breathing. After 15 seconds preliminary mouthpiece breathing. After 15 minutes preliminary mouthpiece breathing. After 15 seconds preliminary mouthpiece breathing. Respi- ration- rate (full min- utes) . Rate of pul- monary venti- lation unre- duced (full min- utes). Respi- ration- rate (% min.). Rate of pul- monary venti- lation, unre- duced (X min.). Respi- ration- rate (full min- utes) . Rate of pul- monary venti- lation unre- duced (full min- utes). Respi- ration- rate (* min.). Rate of pul- monary venti- lation, unre- duced (X min.). Respi- ration- rate (full min- utes). Rate of pul- monary venti- lation unre- duced (full min- utes) . Respi- ration- rate (tf min.). Rate of pul- monary venti- lation, unre- duced (X min.). 1916. Mar. 6 (cont.) 2d min . . . 27.1 28.2 27.1 26.6 26.0 29.5 liters. 50.1 49.6 50.0 51.1 45.5 49.1 29.7 28.4 31.4 29.0 liters. 53.2 48.8 54.1 41.6 28.4 27.3 27.2 28.4 liters. 52.3 52.4 51.1 53.8 31.3 32.0 31.3 28.0 53.9 54.1 53.0 51.8 liters. liters. 29.6 49.4 30.7 53.2 3d min. ... 28.6 28.0 27.3 28.8 53.9 53.0 49.5 50.3 30.0 30.7 32.5 32.0 55.3 54.6 55.0 56.8 28.2 51.7 31.3 55.4 4th min. == 29.8 31.8 32.0 30.3 51.5 56.7 55.6 49.1 34.5 29.9 30.8 31.6 57.9 50.5 55.7 53.9 31.0 53.2 31.7 54.5 5th min .... Mar. 7: 1st min 2d min 30.1 31.0 31.1 22.8 26.7 31.2 26.6 53.6 55.4 55.1 51.5 49.3 50.4 49.5 33.6 33.6 32.2 55.1 60.7 61.4 26.8 50.2 26.2 27.7 29.1 29.4 43.8 49.0 49.4 47.4 28.1 47.4 190 METABOLISM DURING WALKING. TABLE 51. Respiration-rate and rate of pulmonary ventilation (unreduced) in grade-walking experiments without food, for studying effect of long and short duration of preliminary mouthpiece breathing. Subject, E. D. B., SO per cent grade, at approximately 50 meters. (Values per minute.) Continued. Date and interval measured. First comparison. Second comparison. Third comparison. After 15 minutes preliminary mouthpiece breathing. After I. 1 ) seconds preliminary mouthpiece breathing. After 15 minutes preliminary mouthpiece breathing. After 15 seconds preliminary mouthpiece breathing. After 15 m inutes preliminary mouthpiece breathing. After 15 seconds preliminary mouthpiec breathing. Respi- ration- rate (full min- utes). Rate of pul- monary venti- lation unre- duced (full min- utes). Respi- ration- rate (X min.). Rate of pul- monary venti- lation, unre- duced (K min.). Respi- ration- rate (full min- utes) . Rate of pul- monary venti- lation unre- duced (full min- utes). Respi- ration- rate (K min.). Rate of pul- monary venti- lation, unre- duced <# min.). Respi- ration- rate (full min- utes). Rate of pul- monary venti- lation unre- duced (full min- utes) . Respi- ration- rate (^ min.). Rate of pul- monary venti- lation, unre- duced (X min.). 1916. Mar. 7 (cont.) 3d min 28.3 28.0 29.6 28.8 28.1 25.5 28.6 liters. 47.7 49.8 54.3 52.5 49.4 48.9 54.5 28.2 30.2 28.7 29.2 liters. 54.5 48.9 48.8 51.7 liters. liters. liters. liters. 29.1 51.0 4th min .... 5th min 25.8 28.9 27.5 30.5 51.3 49.3 51.0 52.3 28.2 51.0 29.1 30.2 24.6 26.8 50.2 52.6 53.2 48.1 27.7 51.0 6th min .... 7th min 29.5 30.8 52.1 59.4 29.7 28.0 53.0 58.1 Mar. 8: 1st min. . . . 2d min 21.8 21.8 25.9 27.3 42.2 43.8 46.7 51.3 28.9 26.8 28.5 28.5 53.3 50.2 49.1 52.2 28.9 29.1 30.2 32.4 57.2 53.6 50.5 55.2 24.2 46.0 28.2 51.2 30.2 54.1 29.4 30.7 28.7 28.4 51.2 58.7 55.8 52.5 32.6 34.1 32.6 29.8 59.8 60.8 66.7 57.1 32.5 31.8 27.7 29.6 59.4 63.4 59.4 56.5 29.3 54.6 32.3 61.1 30.4 59.7 PHYSIOLOGY OF MOUTH-BREATHING APPLIANCES. 191 TABLE 51. Respiration-rale and rale of pulmonary ventilation (unreduced) in grade-walking experiments without food, for studying effect of long and short duration of preliminary mouthpiece breathing. Subject, E. D. B., 30 per cent grade, at approximately 50 meters. (Values per minute.) Continued. First comparison. Second comparison. Third comparison. After 15 After 15 After 15 After 15 After 15 After 15 minutes seconds minutes seconds minutes seconds preliminary preliminary preliminary preliminary preliminary preliminary mouthpiece mouthpiece mouthpiece mouthpiece mouthpiece mouthpiece breathing. breathing. breathing. breathing. breathing. breathing. Date and interval Rate Rate Rate Rate Rate Rate measured. of pul- of pul- of pul- of pul- of pul- of pul- Respi- monary Respi- monary Respi- monary Respi- monary Respi- monary Respi- monary ration - venti- ration- venti- ration- venti- ration- venti- ration- venti- ration- venti- rate lation rate lation, rate lation rate lation, rate lation rate lation, (full unre- (tt unre- (full unre- (X unre- (full unre- (# unre- min- duced min.). duced min- duced min.). ducpd min- duced min.). duced utes). (full (K utes). (full CK utes). (full (% min- min.). min- min.). min- min.) utes). utes). utes). 1916. liters. liters. liters. liters. liters. liters. Mar. 8 (cont.) 33.5 59.1 33.2 57.4 26.9 51.3 33.5 50.9 31.6 50.7 27.5 52.3 31.8 53.2 34.4 61.6 30.3 53.9 30.3 54.0 30.0 57.2 31.8 57.0 3d min 29.5 53.6 32.3 54.3 31.4 54.6 32.3 56.7 30.5 55.1 29.1 53.6 32.2 60.1 31.1 63.1 30.8 60.5 28.7 61.2 26.8 58.2 29.2 59.4 30.4 48.8 27.8 50.2 30.7 52.6 30.7 51.9 34.2 55.4 29.9 49.7 4th min 29.5 57.1 30.5 55.5 29.5 61.4 30.0 56.7 29.5 59.6 30.2 55.6 31.3 55.7 34.2 59.7 29.4 50.8 28.7 54.0 38.5 71.3 30.9 55.0 32.4 60.6 34.4 66.7 30.4 57.9 32.7 60.5 27.1 65.6 27.7 58.9 5th min 29.1 56.6 31.3 57.7 30.0 55.0 33.6 65.8 29.9 56.4 29.6 55.7 6th min 30.2 54.9 all of the periods for each method of test on these 4 days, we find the average reduced ventilation for the periods with long preliminary mouth- piece breathing to be 45.8 liters and that for the periods with short pre- liminary breathing to be 46.7 liters, with a difference of 0.9 liter or 1.97 per cent. (See table 16, p. 78). At first sight this relatively small difference appears to be a real effect, ascribable to the short use of the mouthpiece. It is important to bear in mind, however, that, as previously pointed out, the actual amount of work performed in the two series was usually somewhat greater in the second set of tests, this difference being not far from 1 per cent. Allow- 192 METABOLISM DURING WALKING. ing for this disparity in amount of work, the apparent difference be- tween the series of tests is reduced to about 1 per cent, which may well be stated to be within the limits of experimental error and not suffi- ciently pronounced to indicate a real physiological difference hi the two methods of preliminary breathing. Owing to the fact that a slightly larger amount of work was usually performed in the second test of each comparison set, i. e., when the experiment was preceded by but 15 seconds of breathing through the mouthpiece, the slightly larger oxygen consumption not3d in these periods (see tables 16 and 49) may be explained without attributing it to the type of respiration preceding the experiment. In the hope that a study of the rate of oxygen consumption from minute to minute might throw some light upon the effect of mouthpiece breathing, such computations from the kymograph curves during grade-walking tests were made. The results which are not tabulated, showed no decided change in the oxygen consumption nor any marked alteration hi the rate of absorption at the beginning of the period. The variations are, hi a number of cases, very large and are probably due. to errors in the estimation of the tune from the slope of the curve errors which are fundamental to the method. The evidence of both the total per minute values in tables 16 and 49, and the values calculated from the kymo- graph curves, suggests no appreciable difference in the rate of oxygen consumption in the two series of tests which is not substantially accounted for by the small difference in the amount of work done. CONCLUSIONS WITH REGARD TO THE EFFECT OF LONG AND SHORT PRELIMINARY MOUTH- PIECE BREATHING. A close study of the respiration-rate, pulmonary ventilation, and oxygen consumption shows no appreciable differences between the two types of preliminary biea thing other than what can reasonably be ascribed to the unfortunate but unavoidable slight differences in the amount of work done. On the other hand, it is quite clear that the respiratory quotient is materially affected by the type of respiration, particularly in the walking experiments, being almost invariably much lower with the short preliminary mouthpiece breathing. One would normally assume that with the long preliminary breath- ing there would have been a period of adjustment, so that with the be- ginning of the metabolism measurements the amount of carbon dioxide exhaled would be essentially that produced. Immediately after the insertion of the mouthpiece, particularly if there is any adjustment of the respiration to the new conditions, as there usually is, one can expect either an excessive removal of carbon dioxide due to pumping-out or possibly the storage of carbon dioxide due to a reduced ventilation. The former is usually the case, and it can be easily seen that the amount of carbon dioxide exhaled would then be larger than that actually METABOLISM WITH GRADE WALKING. 193 produced; consequently, when metabolism measurements are made after a very brief period of mouthpiece breathing, the respiratory quo- tient would be large. As a matter of fact, under exactly these condi- tions of experimenting, we find a quotient somewhat smaller than those obtained during the tests with a long preliminary period of mouth- piece breathing. No simple explanation for this is at hand. These tests have, however, considerable significance in that they indicate the necessity of caution in employing short-period respiration experiments for the computation of the total energy production, especially if the collection of expired ah* is begun immediately after the mouthpiece is inserted. This is all the more important, since there is an increasing tendency on the part of certain physiologists to utilize the carbon-dioxide exhalation alone as a measure of the metabolism. 1 When carbon dioxide only is measured during periods of muscular repose, there is nothing in our results to throw any discredit upon the actual determination of carbon dioxide. Indeed, if the respiratory quotient is determined, it seems to be essentially the same, irrespective of the type of respiration. On the other hand, in experiments in which heavy work is performed, and particularly when the mouthpiece is used, and the whole computation of energy is based upon carbon dioxide alone, it is easy to err in selecting the respiratory quotient to be used. To be sure, in many of these tests only an approximate computation of energy is desired. It is important, however, to bear in mind that in this series of comparison tests there is grave doubt of the accuracy of the determination of the respiratory quotient when the period of measurement is preceded by a very short period of preliminary breath- ing through the mouthpiece. METABOLISM OF SUBJECTS WALKING ON AN INCLINE. In addition to the chronological presentation of the data obtained in the grade-walking experiments in tables 13 to 16, the metabolism measurements have also been assembled in tables 52 to 55, to show the effect of the work performed in the grade walking upon the heat- output in excess of both the standing and the horizontal-walking requirements. These tables show the work performed and the increase in the heat-output. The effect of grade and speed upon the heat-out- put, the physiological factors, and the efficiency is brought out by a summary of the data in table 56. In considering the effect of grade walking upon the energy output as presented in tables 52 to 55, it has been assumed that the basal require- ments of the body at rest, i. e., standing, did not alter during the walk- 'Benedict, Miles, Roth, and Smith, Carnegie Inst. Wash. Pub. No. 280, 1919, p. 119, table 5, footnote 2; Benedict and Johnson, Proc. Am. Phil. Soc., 1919, 58, p. 89; Benedict, Collins, Hendry, and Johnson, N. H. College of Agr., Tech. Bull. No. 16, 1920; Waller, Proc. Phyaiol. Soc., 1918-19, 52, pp. xlviii, 1, lix, Ixvii, and Ixxii; 1919, 53, pp. xxiv, xxx, and xliv. 194 METABOLISM DURING WALKING. TABLE 52. Increase in the heat-output of A. J. 0. and H. R. R. during grade walking in experiments without food. (Values per minute.) Subject and date. (a) Body- weight with clothing. (6) Grade. (c) Distance walked. (d) Horizon- tal com- ponent of distance. () Grade- lift of body. (6Xc) (/) Work due to grade- lift. (eXa) (0) Step- lift. (A) Work due to step- lift. (0Xa) M Work of total lift (work of ascent). (f+h) A. J. O. Mar 2 kg. p. ct. meters. 61.1 meters. 61.1 meters. 2.20 kg. TO. 162.8 meters. kg. m. kg. m. 68.1 68.1 2.45 181.3 74 3 6 64.6 64.6 2.33 172.1 H. R. R. Mar. 27 . . 66.4 66.0 7.04 516.0 1.18 86.5 602.5 66.4 66.0 7.04 516.0 1.68 123.1 639.1 66.8 66.4 7.08 519.0 1.90 139.3 658.3 66.6 66.2 7.06 517.5 2.26 165.7 683.2 Average . . 73.3 10.6 66.6 66.2 7.06 517.1 1.76 128.7 645.8 Apr. 3 . 61.7 61.4 6.29 451.0 1.23 88.2 539 2 61.9 61.6 6.31 452.4 1.31 93.9 546 3 61.8 61.5 6.30 451.7 1.29 92.5 544.2 62.2 61 9 6 34 454.6 1.36 97 5 552 1 Average. . 71.7 10.2 61.9 61.6 6.31 452.4 1.30 93.0 545.5 Apr. 24 63.8 63.4 6.70 473.0 1.56 110.1 583 1 64.2 63.8 6.74 475.8 1.68 118.6 594.4 64.1 63.7 6.73 475 1 1.76 124 3 599 4 Average . . 70.6 10.5 64.0 63.6 6.72 474.6 1.67 117.7 592.3 May 1 71.8 71 4 7 54 542 9 2 02 145 4 688 3 72.5 72.1 7.61 547.9 2.15 154.8 702.7 73.1 72.7 7.68 553.0 2.47 177.8 730 8 73.2 72.8 7.69 553.7 2.71 195.1 748 8 73.0 72.6 7.67 552.2 3 07 221 773 2 72.9 72.5 7 65 550 8 3 27 235 4 786 2 Average . . 72.0 10.5 72.8 72.4 7.64 550.1 2.62 188.3 738.3 May 8 75.9 75 5 7 97 575 4 2 44 176 2 751 6 76.1 75.7 7.99 576.9 2 86 206.5 783.4 76 5 76 1 8 03 579 8 2 95 213 792 8 76.7 76.3 8.05 581 2 3 26 235 4 816.6 77.0 76.6 8 09 584 1 3 22 232 5 816 6 77.0 76.6 8.09 584 1 3 47 250 5 834.6 Average . . 72.2 10.5 76.5 76.1 8.04 580.3 3.03 219.0. 799.3 May 22 66 5 65 7 10 17 720 1 94 137 4 857 4 66.3 65 5 10 14 717 9 1 99 140 9 858 8 65.7 64 9 10 05 711 5 2 11 149 4 860 9 66 3 65 5 10 14 717 9 2 49 176 3 894 2 Average . . 70.8 15.3 66.2 65.4 10.13 716.8 2.13 151.0 867.8 METABOLISM WITH GRADE WALKING. 195 TABLE 52. Increase in the heat-output of A. J. 0. and H. R. R. during grade walking in experiments without food. (Values per minute.} Continued. Subject and date. 0') Total heat during grade walking (com- puted). (*) Heat due to stand- ing. 1 (0 Increment over standing require- ment. O'-fc) Heat due to hori- zontal component. Increment in heat over standing and horizontal compon- ent due to grade-lift. () Grade. (c) Distance walked. WJ Horizon- tal com- ponent of distance. () Grade- lift of body. (bXc) (/) Work due to grade- lift. (eXa) (a) Step- lift. 00 Work due to step- lift. (0Xa) Work of total lift (work of ascent). (f+h) Mar 24 kg. p.ct. meters. 63.4 meters. 63.1 meters. 6.53 kg. m. 367.0 meters. 2.49 kg. m. 139.9 kg. m. 506.9 62.3 62.0 6.42 360.8 2.48 139.4 500.2 62.1 61.8 6.40 359.7 2.46 138.3 498.0 Average . . 56.2 10.3 62.6 62.3 6.45 362.5 2.48 139.2 501.7 Mar. 26 63.4 63.1 6.53 366.3 2.80 157.1 523.4 64.3 64.0 6.62 371.4 2.69 150.9 522.3 64.1 63.8 6.60 370.3 2.77 155.4 525.7 63.9 63.6 6.58 369.1 2.62 147.0 516.1 Average . . 56.1 10.3 63.9 63.6 6.58 369.3 2.72 152.6 521.9 Mar. 30 62 1 61.8 6.33 355.7 2.45 137.7 493.4 61 60.7 6.22 349.6 2 40 134.9 484.5 61.3 61.0 6.25 351.3 2.48 139.4 489.7 Average . . 56.2 10.2 61.5 61.2 6.27 352.2 2.44 137.3 489.2 Apr. 6 62.3 62.0 6.48 367.4 2.48 140.6 508.0 63.2 62.9 6.57 372.5 2.51 142.3 514.8 63.7 63.4 6.62 375.4 2.68 152.0 527.4 Average. . 56.7 10.4 63.1 62.8 6.56 371.8 2.56 145.0 516.7 Apr. 6 58 4 58.1 6.07 338.1 2.30 128.1 466.2 59 3 59.0 6.17 343 . 7 2.44 135.9 479.6 60.2 59.9 6.26 348.7 2.50 139.3 488.0 59 4 59.1 6.18 344.2 2.53 141.0 485.2 60.1 59.7 6.25 348.1 2.56 142.6 490.7 60.4 60.1 6.28 349.8 2.62 145.9 495.7 Average . . 55.7 10.4 59.6 59.3 6.20 345.4 2.49 138.8 484.2 Apr. 7 56 1 55.8 5.83 324.7 2 34 130 3 455 56.4 56.1 5.87 327.0 2.24 124.8 451.8 56.3 56.0 5.86 326.4 2.34 130.3 456.7 56 6 56.3 5.89 328.1 2.42 134.8 462.9 56 5 56.2 5.88 327.5 2.46 137 464.5 57 2 56.9 5.95 331.4 2.46 137 468.4 57.6 57.3 5.99 333.6 2.46 137.0 470.6 Average . . 55.7 10.4 56.7 56.4 5.90 328.4 2.39 133.0 461.6 Apr. 8 67 8 67 4 7 05 389 9 2 83 156 5 546 4 68 67.6 7.07 391.0 2 84 157 1 548 1 67 5 67 1 7.02 388.2 2 94 162 6 550 8 67.9 67.5 7.06 390.4 3.23 178.6 569.0 68 6 68.2 7.13 394.3 3.31 183.0 577.3 69.0 68.6 7.18 397.1 3.29 181.9 579.0 Average. . 55.3 10.4 68.1 67.7 7.09 391.8 3.07 170.0 562.4 Apr. 15 ' 63 9 63 6 6 58 374 4 2 79 158 8 533 2 65 64 6 6 70 381 2 2 89 164 4 545 6 64 8 64 5 6 64 377 8 2 80 159 3 537 1 65 64 7 6 66 379 2 90 165 544 65 4 65.1 6 71 381 8 2 94 167.3 549.1 65.9 65.6 6.76 384.6 2.96 168.4 553.0 Average. . 56.9 10.3 65.0 64.7 6.68 379.8 2.88 163.9 543.7 METABOLISM WITH GRADE WALKING. 197 TABLE 53. Increase in the heat-output of T. H. H. during grade walking in experiments without food. (Values per minute) Continued. Subject and date. 0") Total heat during grade walking (com- puted) . (k) Heat due to stand- ing. (0 Increment over standing require- ment. (j-k) Heat due to hori- zontal component. Increment in heat over standing and horizon- tal component due to grade-lift. (a) Efficiency for grade- lift. 2.34X100 (w) Per h. kg. m. (n) Total. dXaXm (o) Total. (*-n) (P) Per kg.m. of grade-lift. oXIOOO 1000 / P Mar. 24 cols. 5.61 cats. cals. 4.50 4 62 gm.-cal. cals. 1.99 1.96 1.95 cals. 2.51 2.66 2.55 gm.-cals. 6.8 7.3 7.1 p. ct. 34.4 32.1 33.0 Average .... Mar. 26 Average .... Mar. 30 Average .... Apr. 5 Average .... Apr. 6 Average .... Apr. 7 5.73 5.61 4.50 5.64 4. 11 4.53 2 0.562 1.97 2.56 7.1 33.0 5.79 5.87 5.97 6.07 4.68 4.76 4 86 1.98 2.01 2.00 1.99 2:70 2.75 2.86 2.97 7.4 7.5 7.7 8.1 31.6 31.2 30.4 28.9 4.96 5.93 4. 11 4.82 2 .559 1.99 2.83 7.7 30.4 5.80 5.70 5.91 4.69 4.59 4.80 2.10 2.07 2.08 2.59 2.52 2.72 7.3 7.2 7.7 32.1 32.5 30.4 5.80 4. 11 4.69 2 .606 2.08 2.61 7.4 31.6 6.03 6.28 6.40 4.92 5.17 2.24 2.27 2.29 2.68 2.90 3.00 7.3 7.8 8.0 32.1 30.0 29.3 5.29 6.24 1.11 5.13 2 .637 2.27 2.86 7.8 30.0 5.59 5.62 5.70 6.04 5.94 6.11 4.48 4.51 4.59 1.87 1.90 1.93 1.91 1.93 1.94 2.61 2.61 2.66 3.92 2.90 3.06 7.7 7.6 7.6 8.8 8.3 8.7 30.4 30.8 30.8 26.6 28.2 26.8 4.93 4.83 5.00 5.8.3 4. 11 4.72 3 .579 1.91 2.81 8.1 28.9 5.45 5.50 5.47 5.56 5.57 5.79 5.80 4.34 4.39 1.80 1.83 1.81 1.82 1.81 1.84 1.85 2.54 2.55 2.55 2.63 2.65 2.84 2.84 7.8 7.8 7.5 7.7 8.1 8.6 8.5 30.0 30.0 31.2 30.4 28.9 27.2 27.5 Average .... Apr. 8 Average .... Apr 15 4.36 4.45 4.46 4.68 4.69 5.59 U.ll 4.48 3 .579 1.82 2.66 8.1 28.9 6.34 6.23 6.33 6.40 6.48 6.58 5.23 5.12 2.16 2.16 2.15 2.16 2.18 2.20 3.07 2.96 3.07 3.13 3.19 3.27 7.9 7.6 7.9 a.O 8.1 8.2 29.6 30.8 29.6 29.3 28.9 28.5 5.22 5.29 5.37 5.47 6.39 4.11 5.28 3 .579 2.17 3.11 7.9 29.6 5.70 5.84 5.79 5.81 5.91 5.98 4.59 2.14 2.13 2.12 2.13 2.14 2.16 2.45 2.60 2.56 2.57 2.66 2.71 6.6 6.8 6.8 6.8 7.0 7.0 35.5 34.4 34.4 34.4 33.4 33.4 Average .... 4.73 4.68 4.70 4.80 4.87 5.84 4.11 4.73 '.579 2.13 2.60 6.8 34.4 1 Average of the values obtained in all standing experiments with this subject. (See last column of table 4, p. 44.) *Average value obtained on the day of the experiment. (See column i, table 30, p. 122.) 'Average of the values obtained in all horizontal-walking experiments with this subject. (See column i, table 30, p. 122.) 198 METABOLISM DURING WALKING. ing, and that the excess energy expended for the grade walking was the energy required to lift the body to a vertical elevation, this elevation being computed from the grade of the treadmill and the linear dis- tance walked at this grade; also that the energy expended for the horizontal component of this linear distance was the same per meter as that determined in the horizontal-walking experiments. Still another assumption is made, namely, that during grade walking there is a certain amount of step-lift, which constitutes a varying amount of work to be added to the work of grade elevation. An effort was made to measure this step-lift and to compute the work which it represented and the energy which it required. It is necessary to consider, there- fore, (1) the work due to the grade of the treadmill, which is referred to as the work of grade-lift; (2) the work due to the heel-and-toe action, i. e., the step-lift; and (3) the sum of these two, which constitutes the work of ascent. As was the case in the horizontal-walking experiments, the measured value of the step-lift is of somewhat doubtful dependa- bility; this in turn affects the total amount of work, the so-called work of ascent. The measure of the work due to grade-lift is, however, believed to be accurate. It will therefore be considered more fully than the other factors, and has been used as the basis of the curves pre- sented in this section. The method by which the grade-lift was measured and the computa- tion of the horizontal component of the distance walked have been explained on page 29. (See also fig. 6.) With the low grades this latter value, shown in column d of tables 52 to 55, differs but little from the total distance walked. The values used for the standing requirement, which have been de- ducted from the total energy to find the energy requirement for walk- ing, are generally the average values for a period of days, although the average found for that particular day has been used in many instances. The values employed are, in all cases, indicated by footnotes in the tables. In determining the energy to be deducted for the horizontal component, use has been made of the increment per horizontal kilo- grammeter, if found for the day of experiment, and, if not, an average value was employed. When any wide deviation appeared in the values for a subject during the period of study, as was the case with E. D. B., the average value, if employed, is that which in our judgment more nearly represents the average increment at the time of the grade- walking experiments. 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SOO CO ^*O 9 0099rHCM S lOrHOOrHCOlO OCNCOTjIiOCD S 2^22gc?5 3 SS2SS5; S CO *^* t* ^ O CNW^OCOCD SO O * rH Tft SO "5 rHSOCON.S59 00 CONN CM CO CO co CO CO CO CO CO CO CO CO CO CO CO CO CO co COCO COCO CO CO CO CO CO CO CO CO CO CO CM CM CN CO CM CM ri t>.99rHCNCN 000000999 9 9-9-s-9-s g ssssss so 9 00^*0 co OOO SO 9 CO CO CO CO CO SO CO CNOOCO-*CO CM rH O. 9 1 1 ~ I r-l O CO rS i CONCNlOCNrH 9t~OOCOO!N 9 Ci T-H CO "^ *O CO J SO CO t ( CO O Ci CO C^ i-i^ooooco co CO O 00 00 CO I s - OS CO O r-t CM * S SOCOCOCM9 CN co lOOOrHIOCO CM column o lijjj mjr\ O rH f Cpt>CNiOCNrH O0099rHCO SsSssiT i TH CO O3 Ol CO C*-! 9%4r4iHCMP tf COOOO 00 COt- cb COOOCOSM9 SOSOOrHO 9 :::::: SO rH rH CM SO <* rH t- CO table 5, tal walki so .0.0.0 <0 so SO so co co so SO CO W5 ^1-t-OCOlO TH COIOO9CM so SO99IOSOCO o | o g CO -* -* SO t^ 00 SO SO SO SO SO SO so O5 i~* C*l CO ^ ^ so CM co co >o co r~ 1O1OIO1O1O 1 rH019rHr-l(N IO ^ ^ IO IO IO rH 8.9 rHCOCOCOOlO 10 9 ^ 9 SO 00 O 9 lOOOOCOCOOO t- OCMt-^eot- CO son* CM 10 oo 9 SOOOOrHCO US Ji a CM CO CO CO lO CO 00 00 9 9 O O co 9 -"-''-'SSSJS CD Ol (** CO CO t OOOOOOIOrH N -1 rHSOO"*CO ^ rHCOSOOrH-* COCNNCOCO-* CO rHrHrHrHCNCN '"' CM CM CM CM CM IN rH rH (M COCOsOt>.SO SO 10 t>-009OOrH l^ !>!> 00 00 00 B iO II t^- 00 CO CO O O S O 00 10 S 10 O lOiO IO1O1O B5 o CO rH es obtained \i subject of in S G o 10 f o' CO 9 I i ! I 10 1 I Average 51 . 1 d a a 10 1 0) > < rH 5? 00 a oS 'General average of valu 'General average for this 204 METABOLISM DURING WALKING. 1 HO " OS IO * rt N N _ CNOINOOCN OS CO COCOON INOO^OSiO >o d"! 2 g H cxi OOCNOlN-l-H ftlNCOCOCOCOCO ro r- co 10 co co oo MCNINCNININ s Oi OS OS O ^ O iH * p. 05 o 55S5ct?5 00 CO SSf:^S OS M OJ3 ate H s. 2N(NCNoi>ooeococo to OscOCO>-iO OS CO 00 COf- CO lOOOOOCO CO CO IN CO ^TKiOOOOS TH CO OS OS IO CO CO lOt-^lrHCO CM S o 3s o "o S + *"o ^ is !N 10 (NcOOOp--iiO COCO CO CO CO CO CD OS^COOCO co s CO CO CO (O (O 00 CO 4d 3 . " g CO r-1 -! rH IN CO ^ (NCOOS^OOS 10 rHUJWOO co W^l^^W T-l g o X ^g^^^g? 3 CO CO OS O> OS OS s fflOSOSOSIN CO -t r co co t-~ OS O O O O a ^-- -S &S o >O O CO 00 CO CO OS t^ lOCOt^l COCO s >O IN IN i-l 00 O 'O LO O 'O OrHOSCOCM 00HOOi-l 8 M^ JJ IN IN IN IN IN IN o i ^ i:^ 5 w 00 OS (N t^ CO CO n CO SCO l^ OS CO 00 OOSOSOSCO oo OSOOOCO>O 9 00 OS CO 00 00 s |r-t,t.t.t-t. s OS OS CO CO 00 CO CO CO 00 00 00 CO 00 CO 00 00 CO 00 CO 1 'a! (fe * coos-.^co n IO >-t (N 00 >O H >HCOCNt CO CO OiOOSOSOS s wlls?i ^ I s * t*" 00 00 00 GO iO *O iO iQ ^O C | as ggggss? as CO ***** IO ^O >O *O *O * O iO 'O 1 O 1 O o I V o ^CDOO^ r. * CN 00 OS IO CN CO CO OS 00 CO CM 4 t-CNCOCOCO ^ a ^ 00 00 00 OS 00 OS w IO 1O ^3 *O IO O 1 3 :::::: a. o co 'O iOiOOiO>O IO co >0 CO I 1-1 III | s i 1 May 13 OS s 1 May 14 > May 17 ill 8 II a METABOLISM WITH GRADE WALKING. 205 CO OS US PS ^ OS CO CD PS X US U2N CO IN 05 IN IN 10 IN CO t- X CO 1C OS 1C X CO CO at OSXXOSO 00 CNNININPSIN " ! 888585885 8588585858 R KSSSKS 1C * 88885858 CO 8** fc CNCOCN Or-INOOJr-l XO>-*lOIN(0 CO cot- CO to US CO CO ^^t-Xuso, CONCO"*CO ^ COIOt- c 000> N x x x xr x X X X X X X X X xxxxxx X X OS X OS OS X OS xxxxxx 00 oooooo X xxx w r-l CO XOSO f OS XlOX-*PSUS ^< t OS X CO O r~ OS * ' CO X OS t^ US US CO PS CO t- CD CO CO CO CO CO US CO us COPS COCO CO PS PS Tf US US IO CO CD US 1C lOiOUSUSious US ususu, 1C US IO US IO ri 10 S *<<<< * SSScoSS CD COCOCCOCD osescsooo 8 OsosOsCsOO OS O5OO e> 080 8 1 OS 3 1 O CO J I r-ICOXf-XCO PS PS CO CO i-i CO 8tC t CO OS rHOJOiXO 8S33BS PS *OSUJXrHO r-t X ^* rH rH t CO OS 1 CO i- 1 PS X co -IPS US CO r-cO'* CO US CO rH 1 CO D O O n g 1 * si a r-itoxr-xco jj SSS8&SS * 0>USt-US PS >J| OS us X i-i O INOUSCONX -H OS rH US i-l COW 8 XXU3 1C CN- Tjieoco 10 OS ^ Ctococococo r.tt-iet. ^ r-ft-t-t-^ " X X X OS OS X X xxxxxx X xxx 00 xxx X o'C ^H r^tOH^OO <* COXUSOU3.0 r. USOfUSOSOi r-.NIO-.XCO * r-.r-.,.0>t~X PS USPSX >c co^co t. B CO CO ^ CO 1C Ol Oi O O5 b* CO iO i CO Oi ' * (N CS r- CO ^ CD CD CO O s COOSINXINX g^Ss'SsS * * PS i-O 1C CO t US wE2g i feii X "1.9 ^ il UdiOtOtNOO CO 00 O OS ^ O ,H cocorfeococo < NOt-t-NOS * USCOUSOCOIN ^ i-HCOCO f-OrH CO "si ssslss 1 S 3 CN cS c cS -r 01 iillli 1 CO CO CO N CN CN 2 CO C^ CO CO C*2 ^3 1 ill 1 INXOS ^ US 1C COCNtN CN CO 03 J SSS8SS s 3Sx- X CO t^ 00 00 1^ CO p; 5SSS s SSus'us'lo-g US CO OS I- PS PS US t-OO s 1? TJ^^^COCO * ****** Tt< '*'"*'*'*'* "* ^^^^,^,^ "* "' l " c US ^UJUJ "* 'Si COcOOGS-fX r. OOUSrH^CO CO (NWCOIN^^ O <3>X>*Ot~ CO COX Oi O3 * ' CO t^ ^rHCO CO US THUS US g'g COUSUSOXPS s OSOOCOlOt- 1C iC O iC 1C 1C IN s OSCOPSINOOS CO T* IO h- i-< CO O CO CD CO CO CO CO to r t < ' CO CO CO CO 1 coco' co CO CO CO li co CNOSIN SCOPS COCO i II SiN22S 8 CO. Tj< US O * OS OOOi-li-lrH g Sco^SSi: IN CO ooSSSSco 1C OSOr-IINCOPS OS S^o COPS N cor- co COMCO CO 3 a! . OS OS OS 05 OS 0> OS oooooo O oooooo rH IN IN (N IN IN CO r-tNCOMININ CO CNCOCO N CO IN IN IN 5 c e-2 . CO US ^ OS COO l-X t-PSt- CO -g.S"2 O O5 OS 00 00 CO Os WCOUS X coosiN^Psr- rH^Xt-CS ID OO-* X CO IN CO US "a CO COCO iO lOO s IO US >O US CO CO CO CD CO CO CO CO CO CO co 1C CO t*- CD CD c ooo xxx 8 CO US rH es obtained w subject of in >ee last colum May 18 PS May 24 3 May 25 Average 51 . 1 May 26 00 1 May 28 ! May 29 1C 1 O e 3 CO rH IO i < 'General average of valu 'General average for this Average for the day. 6 206 METABOLISM DURING WALKING. K o a 8 4- X (N o>n to os to to co os os CO P5 CO I s * Ol CQ *^ r- 3 '3 M njia x ft Jj * S * R8 * to to to i>- to >o ** IN IN IN IN IN IN to 5DcO*O^***OC wwcawww (N -fe^- Is, "iio-ooo to t-OS 00000 rH co ^00 00 OS -** OS O 00 <-* ^ CO C^ __, g"_lo ti tif"* ^ '.000000 K CO 00 CO 00 00 CO O> oo 00 00 00 00 OS OS X 0000 OOO Ol os ! ft ~ o 3 f . CO 00 O) 5 ^Jo^NCO g CO-*COOOCOrH i-iOO>'Ot--00 co 00 O5 Ol O ^* Oi^HCOWW 00 JoSS-^3 5101010 *'*'""* ^^co^^.^. 1 * IOWI 10 IO o .3 fl 7 3 x ,2'osoo 8 (N IN IN rH r-C r-l 8 f-Hr-tOWNN - CO CO CO CO CO CO r- CO _*_JP grHNN "g S'gl^|2 8 : : : o J i 1 V -i? &! * 7 .^ooo OOrHINOOOt-- 8 00 iO H C^b* ^t NrHOOOOO i COT(lOOOlNO 5 S 8 [Pg i gr-t-t- * OU500U50 >o iO iO O >O LOCO id to to to to to to to I 1.1! \4 ' rH o "3* . -So , Sf a i^a j.S-a^S^ -99S - IO >O tO s 00 *O -^ C^ t^ ^ CO O H to CO "^ *O 0000 O J : a h os o a a M &~a 000000 CO to to to to to to to tOtOtOcOt^t, to t-t-t-t-t-t> * "3 X, .10 to to Cl rHtOSOOOSOO as OSOSt^-*iOlO to S 1? s ^l t && ggiiii I IO"OINOONC<) Tj* OOINlOCOt>.CO 00 00 00 00 00 00 to IN 00 JJ o o gi-ttOOS IN rtt-INTKlOCO o toooco-*>o >0 100^^10-* o S 3"^ 3 jflig O) 3 N (N IN rH IN M 3 N co co COIN com rHrHrH(NN(N 1 t to oo >o os 10 (N N IN IN IN IN i ^ M! gffSfi cooo>otooo OOOOOO3O a> tototoco-^S? s ososcocooco to ^^ *>^j i^ 1010 >0 co COCOCO^TKrf * Tj* Tj* IO O O O a .* x * j . gTHOt- ^ OOt-rt.^O r-l (N rH tO i 1 r-t O O5 O5 CO 1 Sllsss 1 iO O O O iO *O s IO ~ 1 2-^ x fe-H^CO 00 N to CO to tO co ^(NXOCOQ CO O t^ rH O O s CDOOOOOOO 9 C g^rHt-l (M ii OSOOSOSOSOS OS Ol Ol 00 O O O 0> SSSSS^! a . 3-A JJNOS.O O! O5 r-t 00 C> 00 CO to OONOlO^O 00 rH 00 00 00 00 00 o S 1- [fill |?2* 00 * 5 -*^^ 5J ^^555-5 to ssssss to , v~% 9r-IOOlJI 00 OS rH 00 OS 00 CO to t-rHOSlOTKO 00 COOS OSOOO HI i o 3 : : : p. a: "O tomcoooo t^totooot^t^ IO *O lO !O *O >O s ll 3 i CQ B'S o =1 ^ ^*3"" ll M I to 10 > V a "-s "0 > 00 g 3 "0 < os' to 1 00 * METABOLISM WITH GRADE WALKING. 207 0 OS OS OS Ol OS OS OS OS 01 OS 01 01 OS OS OS OS OS 00 OS OS OS OSX 00 00 Ol OS OS 00 Ol OS 00 00 OS CM CMOS CO CM t- b- oo r- as os oo co 00 oc oo cs co co CO Sc?Sc3 i 88. s COOiCiCiCCO ft 00 CO 1C OS CO 1C 1C 1C 1C O 1C 1C 1C COOCCCOCO CD CD CO CO CO CO CO CD t-t-t^ * CO CO CO CO CO CO CO CD COCO 1C 1C 1C CO 1C 1C 1C 1C 1C 1C W*!53 s OOi-HOOlOSOS t-oooot-t-t- S O O5C1 01 t-. CM I i-t t^ t- COCOCOCOcMcN COOt-CMCMO * * CO CM (N CM CO g a CO 1 1 H \ ; ? 8 | CM CO CO * * CO o CO ss~~8* 5< CMt-OSt-CMCO s o2co co I ::::::! OCMCDCOCMO 00 2C88SS? I * a E M*X t> OOOOOOCOOO w o 000000000000 00 00 O Oi o> i 2? I ;;;;;;! OOOOt^t-COCO o o i a- B" f -1 :::: i'l s 3 Si 35. SB? 00 CO <-< CO-* COt- OOi t-i cM^OSt-CMCO C 00 1- 1C cot- o2S? CO owcocogo CO "O SSSS8S "cct^w 000000 000000 00 OS OS OS OS OS 0> OS OS OS Ol OS OS 01 OSOO O5 00 00 00 00 00 CO OS OS CO 0000 1- 00 5 5 rHCOr-CCOCOCO n OOOOCOO rH 00 1C ^ CO ^ OS H CM OS OS t^ CMtMOOlCMt- t> Oi-(iOiOOOCO 1C Is OcDO'j'oqoo CM CM CO 'f * ?5 OS OS Ol Ol Ol Ol 1 ?isii i So? t- co x r-- ooooo i 222 1 oocooococot- t^CMOOSOOt- OS OS OS 00 00 00 s Oosoioooooo co 28 II II ^.01 Tf OS OS 01 CM OlOOOOCO 10 co r- co w CO CO CO CO CO ic CO lCCOcMcM-">C CM * CM (N * CO CO CO CO COCO CO g CM 1C 1C CO COCO i 1C CO i ' i i ' O CM CM CM CM CM CM 1 00 CO I s - CO QC O os Eg gen 1 (O I s " CO CO iO CO 5&3S8 SSSSSco ESS SS r ci co co CM i< 5 Oi i-t-* CD CO CO s By o5 IO tO CO O SO O CO t-l-t-coco N CD CD CO CD CD CD CO ot^t- CO *'<"*'**'* ^ ^^cococo CO 3.1 t-r-t-t-t-i- OS OSOSOOOt- 1. rtt^O^^TX CO t-0000 T 1 CM^COOO^-. 00 oasoo^aox o si CO CO CO CO CO CO CM s t-t-t""> COCO 00 t-^t-t-t-t-t^ 1C t^ Ol OO t-0000 i8 CO CO t- -* I"* Ol Ol 1C CO (NIC CO CM t-r-r-cococo OS s fl ~ o OOOOOOCOOO co co iC 00 1- eo s tfOOOOCO CO CO 00 00 CO CM co OcMCOOQO t^ OS 00 00 00 00 s CO COO t-O3O os COI>CDCDCNCN s O1CD CO Ol t 1C o H CM CM CM CM (N IN M **<< co co * ***-* Tjl * < 1C 1C CO 1C ^f CO CO CO CO CO CO * * * CM CM CM CO ^^s ^t-COt-10-. ^ t-csioeoos H Oi-HOSiCiOiO CO CMCM-cK 01 *coast-Tt.Tf 01 OOOCOcMCOlC OS d -S.2 N -< 1-1 CM (N CM CM CO t~cOcO CM CO CM CM CM (N t-t-r-t-t-t- s t-0000 iO iC iO lO^OiO s OOCO1CO1O100 (N w a-g OJ.^ ^ *^O OlO 00^* 4 (N-*OOCO co OCO^OOO H ooooo 1C (NOCO^-^ CD ost-n-oooi- 00 2 g "3 Sja CO CO CM-* CO CO co CO CO ^ Ol 00 rH CO **>*<<* * XOSO 01 t^ 10 TJI * CO CO j5 J3 fl 4f] OS "3-S {j| v . OQ June 17 ! June 23 OS General average 'General average Average for the METABOLISM WITH GRADE WALKING. 209 * , 8 ^ g ^ +z ^00-*Tt<0 * oooooo < 00-*0t- CM *NO^ CO 0-H10-* IT^ 3 " CN . ^H OOOC*O e.^ co co 9998 ^ CO CO CO CO co CO CO CO CO CO 813$ CO ' o 2 sis 2 i 8 " G M .n a! S " "^ -<">-. 6 ^ N |L wo CNrHt^Ol co rHCOOOO 4 Ot-OrH 01 2 a -'&<. 2a y ^_T3 MM A a a * * 1^3 CO CD CD CO ' o o o o CO CO COO co CO CO CO CO CO C00 10 N S "3 8 fci l>.2 *TJ C" 1 . O 05 00 CO oCO CO CO 00 US fc t-r-oot- S t'w O5 ^-< CO g 00 OOt- 00 3 S5.S&& Ha So ' Si , a l .JlOCNOO g 00 CO CO CO 53 TjtrHrHO H CNCNCNCN CN 3 g- H X- |l e ^ ~ *s |I * ** | ': ': \ ': 5 1 -. B " .a J 1 Q) *T^* .iHiHOOCO , oo oo r- oo 00 SSS2 co >< O CO CO QkQDOOl (N Ol ^OCNCO cn 2S8S w t-t 1 CNCNNCN (N 1. ... !. . . . C4 * T-| \4 ; : : i" ;;;:| i- 2 2 3*.s-SaS'8 . 01 d co ^ ^e 00 00 COO) ajjsgjj CN .... O5 O5 O O 8 . . . SS8S g 222S: CO H-S|&|I1 SCNCNCNCN CN CO CO CO CO CO O) CM CO CO CO CSCNCOCO CN CO CO COCO co' a ^ . ~ .00000 _ UStHCOIN O co^.o-. co CNCMCOO) 01 (Nt-COrH H s |^i|ol + ^SSCO s COCO--(i-l C^!MIMCN co 8 OSO1CNOO CN 00 SS?: S 00-jllC-* o>o o>o) ^o "- S ^ * j,, , 7 gCNOOCOO o 00--lO>IN coo^t- 1-1 Or-iO-* H r-lOOOOO * Ijf* 2 4 o oct-t-oo OJ OlOJCOlO US U5 CO CO s S5;ss O 5SS3S JS *"* Q< A gSSctS s CO CO CO CO co SS2 s ooo^t QbflDQkw g So'ctS ^3 a 'wo 1 H ^^^^ * ** o - Jd* i gOOt-U5>0 _, t-0^0 COCNCOt- CN CNO.COO t^ ^t^"5CO ^. S |||| x ci22^^ CO 5^55! 5 OOiOOCN CNi tr-tCN S CN^S?3 3 3^' s M ^ ? &* X ?i co 0> 5338 5 g S 22^ CN ^55!g 1 |sl e i "* NNNCN IN CNNCNN CN CNCNCNCN CN CNCNNCN CN ! j Q | . COTJ-OSO. o eot-ior- CO Oi "^ CO CO 00 OCNO* 00 ^* Ol O* * 00 CO 00 ^ 03- 0) ^eo- CO COlOi-Ht- CN 2 S H gcocococo 00 CO C7S OOOOt^ * 1331 J 5^95! 9 9995; 9 S" 2 " O ts . . . . A o o li 1 o n,l ! O 3 2lH? Ill o ooo-oo 00 -KOTtl^ 10 ooooo^ ss .CM rococo ROCOCO CO Rp^ 1 C3SOOIOW5 5 coiooos IN $&$$ Mis. 3 "3 IONICS 00 CD CO OS 00 CO t^COCNCM ^ Naoos 10 cost- co 00 IO CD CO CD co ^1010^10 10 TfrfUSW 10 U5U5U3U5 >o I||S| "- "B ? >S "o J, .sSfcSS CD . . . . 10 {2{25SS oo r- CO 00 OS OS X COrtlOOO 8 . go Heat due to hori- zontal component. * III ,OC-f i-iCO s CO IO CM CM OS CM CM CM IN i-l R CM os os r * CO CO CO fi CO CO CO CO IO CO 5-^ss o rH a : : : : ia 1 ^ v : : : : s : : : : ! ? s .CSi-lOCN ^e 00 OS OS OS CD CD CO i-l CO Os O Os OS OS i-tiHOlt-l r- IH CD OS OS CO CM i-l CM CM ct lOWOOO CMCMi-iO OS CM O ,_! ,_, ,_( I-l 1-1 rHN '~,' H _ H CM CM CM CM IN CM CM IN CM CM CM CM CM CN S 1 IP If:::: 3 8 8 8 8. Is H.S Jiff! .r- os coo joOSOsOsO 8 OI-H o oo 8 "5CMCO-* CM CM CM CM 8 CO CM CO CO IN CO CO CD CO CO COCOCMrt CM CO gcMCMCMCO CM CO CO CO CM CO CO CO COCO CO CO CO CO CO CO CO CO CO CO CO "o H I .r-ICN3r-l CM * COOS'*'*' r> O-*ICMO IN OS iH CO OS CO CM OS CO CM i ja^inSi-l g O O OS OS OS tNNr-li-1,-1 8 cs COCNIININ CM CM CM IN CM CM 10 ^ co co CM CM CM CM CO XO5CMOO CN CM CM CM s- s 5 ^- x *tz o o o **- ^> gCOOOCDUS H OOCMO>OO o: O5 00 CO CM ^ Tj*^ 00 iH CM TfWlOO CO 00 5 * CM CM 00 1--* OCO'O'OiO S8 tfOCSCO CM OSOSOOT-I cot>-t-oo S OS CO CO O t^xxx 3 || J- 00 00 COt- B t- CD OS CO CM OO OSOSO) 8 t^, O X'* 1 CM CM -< CM IN CN CM>0-*00 IO CO CO CO IO CM CM CO os i i-l i-H 1-1 S |||| x giOfCsco H OTJ-* X rtCOCOOO O lOt-WOO H 00 * 00 CM i .COiJ'OCN OCNCMCNCM e( ^^ooj^ 3 SSwSS a ce cotoio CO COCOXOO COCOiOlO ^"o >. v * lil 2 JoOCOt^O co OOcDOOTf 5 00 CM CM OS CO CO CO IO s OOlOCOO s t-COOOS 00 00 1 CO CM ^CM CM CM CM CM tN CM CM CM CM CM CM CM CM CM CM (NCMCNCN CM CM CM CM CM s H fill WCSIOCNOS TH TfOOOOOCD H TKCMCMt- lOX'OX t. CM * OS CD CO s |99 9 Osost-^cip sg CO CM CM rH lOlOLOLQ CM 10 ssss * 'Eo-SSS *^* .! ^^^ C il o O r** ?o X ssss CM "O ssss 3 r^- CD "^ co S 1 O R. >0 10 10 o ui 3 iflp | *;;: = X IO as r ||j 00 2,0 I III < < i < * -5 i 1 & o g V *r *r tr -*-* ft i Wt *4 METABOLISM WITH GRADE WALKING. 211 -lt>.00t>. OS <*COOOO hi *t~ON 00 CONOCO o lO^iOO < *10-*IQ ^*" miQIQtQ 10 TjtiQifllO 10 **<(* * CD COO t- C00t^l> o cor-r^ t*. Scor-r- osoo 8 eo--i--r- CO t r-cot-io t-t-r-t- CO B t>-t^t^00 os os os os a ssss OsOOcD 00 00 "5 "5 (N- os os --1CNCNCN co CN OS 00 OS OS * *OOOi-i CM CO IN CO s IOIOCOOO 00 00 OS OS 03 COt~-"5O r- oo oo os 1-H * 00 CO CO CO CO CO CO CO CO CO CO -r-r * **** * CO *** * ^""^^ w co co co co CO **-** * CO r-oo-*M "O OOO OS CO co Ht^Nt. t OS OS CO OC 00 COt-COiH OS CO OS OS CO -* OOOCON -1 o> COP) OS 05 O CO *r~f-co COCO CO CO IO CD CO 1^ CO IN IN oooo-. ^* ^T CO CO 00 OS 03 COCO CO CO 9 co >OCOt^O ^^^^5 i 00 CO H 005O>^ OJ OOOt>.iO 00 CO CO 00 1** CO OS tN IN CO * i-Ht^Kor- OSOO-* 00 010-*^ 00 S3 8 lOOtMrH r*rtOt-~ 8 COIN CO 00 iciomco 5 HTtl^O CO CO IO CD ^ "O CD * COOlOCO i-l<-tOO occ>nt~ OS 00 OJ OS tN OS ^t^-OiO *T)nO-* $ COI>- 00 1- i togioN OOOt^-cN t^ cNosr>-t~ CO >O CO 00 ojr-^-i-H t>t~COt^ N. OT-ICO'H *COI>10 s COOJOCOCO O-* 3 CNtNCNCN O * OJO^-"-* OS ^ OS OS OS >0 OCOCSi-< CO t^CO-*IN Ol Ci d O * o , 1 CM CM COO O5 Oi O O5 CN 2 t^rt>-t>- CNCNCNIN tN i-lNtNCO CNCNININ CNCMNCN a IN Cj?O IO OS (NNNCN iO N *cor->o os os oo oo INCv|!N(N 1 >O 00 00 00 lO^Tt*^ CNINtNCN s CN ,-IOCO>O ^t 1 co co co COCO CO CO s DO5Ot^ CO IN CO CM co CN(NCN.-* iot, tor- 5 OOOSOO o o oor^t^-r- CO IN IN (^.lOXJiO CO o>o-* CD CO CO CO ijj CO CO-* CO-* t^tt^r Tt< r^ *^tTj(O t-t-t-t- 4 t> O'OiO'* t-I>t>-t- co B opoo^t^ **** r^ 41 9W5! 5 r-ococo IQ lOtOtO CO "5 i-"OOO5CO O >o OU510-* CO OOOGt^^ ? N^^l^ f-f-f-eo B o o CO ro o "O 10 3 10 iO 1 . . . . rH o i-l CO 3i X) 10 00 10 ::;: co >0 S i > o Z Average M cS Average CO z Average IO 'Z Average T(.~lt-. 10 OO-KIO^ OtOCMCX) __, r-^t-GC CM CM .COCM-^CM ft.CO CO CO CO M CO CO CO CM I CO CO COCO *< t_i M c-c a M gtMCMCMCM CM CM CM CM CM CM CM CM IN CM CM CM CM CM CM CM " CO CO CO CO CO ii = 3 i .2 co co co co fc n f -.1 -. co cot- co o ooooo oooooo CO CO CO CO 221-2 2 i! ' s i - 3. o tM *> -^ t. . M 4) P -i. CL _^ a a 3 .... v : : : : S ?| .CO CM CO IO ^2 co ooooo 00 CO^SS 8 3S5988 5 CO-* CO CO CJ OOCMCO co lso|- s |s i CO CO COCO CO * * -*-*-*Tj^ "**"** rf .010100 o s |f|i i\\l\ #1 * O rH 3^ c |si .-S8S8 00 SgSg o CO S9S88 s sssss S OOCMCO lOCOt-00 CM 5*|l|If * 1010 a IQ 10 .01010.0.0 10 00^510 IO CO CO CO CO CO a j- i a OlOOt- IO ^I^,H CO ^^^ 8 b 54 1 t" 00 d OC lOtO lOiO iiiii 00 i t^ ooooo IO IO IO IO CO s f-OCMCO M O . C5 ^^.USCO * 30-toao oooiooo 00 r->0>*# ^ Ot-t-CM CO fe 3 -2 5, .CO--IIOCO 3 CO CO d CO CT. SSooo* co 00 00 Cl O O s S333 "0 s_ "* '~ t '~ < CM 5 ^ gS3SS CM O WCO H O 10 s^ss s COrfOOO t^ OOOOO S 01 & ! IO CO CO CO CD CO cococccoco CD CO CO CO CO CD t-t-l-t- 4*3 . CM^O-t H 00 CO .0 CO 00 h- s 1 O ts . . . . O o O JJ 5'jj'C O G ill! 8 8 8 CM S l-ai I s - IO C^ rf Average o Average si 1 Average 5 Average j Average "O 05 METABOLISM WITH GRADE WALKING. 213 or- * OSiOiO^ o 0.-'l~ 1C i-l t- CM CM Ot^^CM 0^0 T* Of-CMrHWO CM .ONt- ^ 5 3 -S 3 *O o9 ft .O & ** O coco--* CO CO CO CC CO COCNCNCN CO CO CO CO co CO CO CO CN i-l CO CO CO CO s CO CO CO CO CO CO CO CO CO CN CO CO CO CO CO CO CO CO CO CO'-'i-tCNOO COCO CO CO CO CO co CM-H-H CO CO CO CM CO 0,4 fl J3 CD S * 3 * 0~ OS CM CN CO O-HCO-* CM * f rH^CO.0 co rHO^I o i-l -*IO CO CO 00 1C CN.C-* CO i ** p D. ' ' o ^s a g j P ' CNt^O COCOiO 8 OSCNOO t'* OS OS OS 00 iC OS COO OSCSO 1 g OCi-lCNCN 00 OS OS OS S SgS!J 1C 8 CM 00 ost^- iccoxr-ooo oo *coco 1-1 CO CM CO CM .2 S a CO CO CO co CNCNCNCN CM CM CN CO CO co CNCNCMCM ti CNCNCMCM CM CO CM CM CM CO CO CO CO CO 'i* CO ^.^^ "* II n* -1 S c IM fe gScN CN OOCM.-I s sssss c CO 88Sc5 O csos 00 CM C! ss?; 8 3%M$3 fe CM CM OS CO CD 1C S Ju l ^"d "^ H r^ a> i-* OSTJ 0> - : 1C - ~ i .is si a 32 S-g ^ |i | 1 CM OS .-1 s OSCNCNr-l TjICOCOCO 8 00 00 00 OS ss "siii" OS CS -HOOCO COCOCN CM i- 1 OS g OCQCOi-iCOiO CO 1C CM t>OSOO H 00 2^ 8*9 If! "8 1 S 1C % Tt< TJH Tf * % co CO COCO CO CO 8 ^ ^ CO 8 o oo o o 10 1C g CM . SQ o *"""* CO ""* ^ g nil g S _ 3 -* co cor- CO r-ooos CD CC CO 1C CO 00 OSOSO 1C OS sso-o- ^ OS 00 00-* s CO CM afe 333 8 *coo OOOOS 1-1 CN OS . ia - B O 50 w "a ^^ "S CO CO CO CO 1C 1C 1C >C 1C IO 1C 1C CO IO IOIO1OIO 1C *'*'*'* t 1C iC 1C 1C COCOOCOCOCO CO cor- co CO s fl is 1 0>CO OS CO ^* CO CO OS 0^00 00 OcoOi-i * COTK^X CN COITUS IO CDCOOCOt- CM 1C COO o II II 1 CN^JCO co co I>- t>- OS CM CM I-H CM CM CM CO CO CD CD CM iH i ICO rHi-IOi-l ^ S3S CN CO rHOCO^* CM g 8 *<' * * CO CO CO CO co CO CO CO CO CO CMCNCNCN CM CMCMCNCN CO COCO CO CO COCO'* 1 0] ^ssISs 1C OJ 00 00 10 a 8 -d ^ .2 |l II i . -HCDO ooo s oo oo coi^ S3 oSoo 1C o CNOCOO ot^coco CD CO cNo5{2Ej CO oo CMOCD SSSStSoo s 2 P ifl is 000000 00 CO CO CO CO CD r-t-J-t- * CO CO CO CO to CD iO 1C 1C 1C t-t-CO CD 1 oooooooooooo CO OOCS o 3 . ha o. t^CNCO CO TK^OOCO co^ooo H COCMt-5 0> Ot-ost- co .c^os CS OOOSOOCX)^^ CO ^co rt a JS S So oc OS CO CO CO CO CC CD OOOsO t^OCOb- 33^? co 1-1 00 1>- CO ^ CO CO CO $ t^COCO 1C CO ^ t^ ! t~ 00 EC SSS!2 CD CO CO CO CO ^S S S^s 9-S Si s gs 4 ' M . i-l COO o r-t-r-iCO co 1^00 CM-* c OOt^CNO U5r- S?" 1 i 1 CO i s 1 CM d O Average 59.1 CO B -f IB I < d Q iC i I < CO d Q CM 2 a I < 1 o o Q CM i < OC o I Q Average | 58.4 M d o Q 15 t~t o > < J Average of values obtain >Average for the day. cilogrammeter in horizontal 'Average of increments j lorizoutal walking of 43.4 to i 32, p. 126. 'Average of increments p walking of 74.8 to 79.3 metei 214 METABOLISM DURING WALKING. 8 c O> * si .CN>-<(N(NO RCOCOCOCOCO CO r-l ^H rH CN i-l O CO CO CO CO CO CO co 1-1 .-i O WOO CO CO CO CO CO CO CO CC CO CO CO CO -^ CO CO CO CO CO CO co co co co co * co co COCO CO CO CO CO Increment in heat over standing and horizontal compo- nents due to grade-lift. s s a,? a M - ^pii .'Q y 1 fcr w XN ^& "3 t- ^r^r-t^r^r~ o r- t-t-tt-t-t t~ t~t~J~r-l~t~ N ot~tt-tt t^ r-iteococo - 1 7 ~ ^ i O5COt^CN'-l ojiOCOiOOOO C\l CO OCOOOJX^ cot~cOU5r^O5 T)< t^- 00 * O) * IO IN OOCOT(< S lOiONXO'* iNco--ie<)Nco o cs 2S83 CO CO g -^ * * TJ * TT Tj< * Tj< T< Tf ^ lOiOlO'iJUOiO IO ****)<* Tf CO CO CO CO COCO *i 5 ^ 5 t l| ftl i 2 I e i. H X - w * b ! _-COilOQI IN O) COCOCOCO-*lO O5 O5 O5 C35 O5 Ol * f-r-oxcN.-! OOl-lOr-<,-< N 1-1 in o> a> e> CMOO5OJCN slOCOTtc*t^ 9 s CN O> CN CN O) O> CD CD CO "O t~ 00 00 CO lOi-lO>CNt^CO 1H1-HCOO--1HO 0> (N t-eot~t^mo itOCOlOiO) IO IO COCOt~.iOXX r-i o> O: CO CO iO CO CO * 8| g CO CO CD CO CD 4 : : : : : s CO CO CO CO CD CO CD s t> S lO'OiCioiOiO 10 8 * CO CO **( * fi|F s jiff! 8 oxtoo CDCOlOiOX 2 OtOQOt^ t^t^-t^COXOl co t^ COO>tOOi-< CNrt-*^iOCO t CO >o^i;ioeox to t^ * cc to to 2 Tj< T)< IO CO CO CO tOOt-t-CO -1 1-1 * IO gb-r^r-r-t^ t~ l^r-t-^t-t- t^ 00000000X00 X CO COCO CD CO CO 1OIO1O1O1OU9 3 |li ^ a * * |o + ^ .CO-^OIO--! 10 TjlOOTttr-lO N OJO^CNOCO >0 CDXOt>Tt IN XO5OOOlO * * ^O--N- 005CCIN(NT-I co t~ f~ co o> oo (JJ Oi Oi Q} O G3 10 s COlO^-llOCNCO CQ * * Oi rH r- ( Q> xxt^xxt* 1 00 O5 O5 ^ CO O O 00 00 W i tO to 10 10 1^ t^- 1* BS^ & |*a 2 gCOt~COr-lX * tTf Or--* co t^lNINt^OO IO CO NlO O O> ft H tNOCO^fCO-* CO . O5XCO CN CO cat* 1 " t*~ X X X rfeCNINNINCN 00 r- r-< 10 t^cor^cooci^ CNCNtNINCMIN * t~ CN i-lNr-CNO>O Oi Oi 00 00 O5 O '-iO5XCOi-Hi-l Xt^OJt-OO g OiOi-HCOINCO rH IN .-< O CO rl t> * rH lO ^4 rt tO 1 s * COCO X t^*O 8 ^ o> co 10 >o 1 ***** ^ *<** 10 * * >OiOiOiOiOiO >0 CO CO CO CO CO CO CO CM CN CM CO CO CO * 3 A . s liF 2 gOt^t^-*CO o r-icocorfoeo ou C^OOO9>OOCO OCOIACNIOX rt CO C35 CO rH * rt l-l s Td .r-l(NXtNiO A; co co co CD co s co r-(NOO>- cocccoiNroco s CD t* 00 00 1"- Cl Ol i CO OJ lO *-t W t* CO CO 1C CO CO IQ CNOXINCOO m COIN IN i co TjctJi^lOlOVS ? i-i x ySJ ;2. ^2c5 IOI-TlOlO.- o * ^COCOCNCNCN O * ^f IO CO tt-t-tt^t^ 10 t^ t->-lOCilN 00X000000 1: : : : : : 00 o *T)O >O IO U3 s o c35t>.t^iO>O^; CO CO CO ^ ^ "V 1 o "8 a 10 o 3| Him m M 8 CO CN o .SUSS M A IFl* 5 : : : : : (^ IO J 8 s 15 111 I 1 * s i i i i i S 1 ^co |r. | oo r < ^ ^^ ^^ -S- 1 < S S s g g Q Q Q Q Q METABOLISM WITH GRADE WALKING. 215 OOO^t-CN iO r-l 00-* CN lOt-t^ -H O4O M CD CNCN M rHCNCN OTjICNCN o ' 'O J ja . co co co co *-* I-H CO CO CO CO CO CO a CNOO cococo " CN-HrH CN COCOCO CO 00 1^ CNCN oo O400t> CNCNCN S CM r^ r-l COCOCO o O O O4O4 CO CO CNCN o CO ^-CO ^ o ^SCN col I* rHr*r-.0-*IO CN CO COt- 'O (NT*,* CO r-llO co O4COCO CO CO 10 10 10 OOt-OO 00 j| hf t-^t>OI>t- ^ t*t.f *" t " l ~ l ~ *" 0000 00 t-0000 00 t-t-t> * t-t-0000 *" ^ Q>xi 5 &A MO] d fl fl-** CO DQ O * CO *"H CO CO CO CO I*- 00 g S2S s OOOO4 00 U5O4 B r-t>.oo CNt-i-l ^ CO 00 CO COCOCO CO O400OO oo 06 |fl l| 101010101010 10 IOCOCO CO IOIOIO IO t-t- * t * t " 00 * *"*'* * cocot-r^ CO il ^ CN CO CO * CO iO CO CO CO CO CO CO CO OCO-* R Oi O4 CO O cocoo t^- ss CN CN O4CNCO i-l CNCN S5 222 CN *Xt^CO CD iO .3 1-1 .^ co U1-I S02 rH ^ - 2 .a Jj2 IO CS 00 9 3 ... 00 : : : 1 i i . cq CO *O CO CNCOiOiO 5 21 11 04 g-g -04~ gt 1 04O 04 O5O4O 04 IO1O1O IO 00 00 00 00 00 81 5.9 t,eo w T " - I : : :|g CN 04 CN 9 A d ^ S"5 3-< 1 . W COOjOgjO"*! eOi-lOlOlO CN CN 98.5 00 SS2 S oo IOOOCO COrHCO co OOO4 8 CNiOCOlO S P 2 11 oS 68 S-S "S 000000000000 00 OOOOOO 00 OOOOOO ot O^ a OrHrH 1-1 >> ^ Oi O4 O4 OS 04 -> ^1 CN1OO40000CO 04 cocoo ao CNi-ICN U S 0004 ^ U5M.IO 10 t-COO 000 -H^l lO I 2 l oooooo CN BBS 00 B OOO C OiH C i IOIO 1 lOiOt^- CNCNCN CN 00 00 00 S04 *OOOOO4 1OOOOOO4 s 3 a ^^ o !" al -S OOOOO4CN1OCO CO ^0* 04 OOCO-* C 14 CNt- ^ ot . t-CNOO 04 Ot-0004 rt li SI co co co r- < r-1 oo O O4 00 00 O4 00 CN CNCN CNCNCN C4 oo CN IOCOCO oo cor-- CNCNCN *r** 10 u O4O404 C CNCNCN C 5 1OO 4 (NCN J CNCO co CNCNCN COCO CO CN CO SCO CO CNCN CNCNCN CN CN O4O-H(N CNCO CO CO o CO 1! 15 -C M Pi.-** t-l r-l C34 O4 > CN iHr-IO400OO co o O4COf~ OC fHCNCN C 3 OOiO O4 CO SiOcO iO lOOOOO "O ocococo CO O 0> M oo^.o.o 10 **# * IO IO *O l 3 COiO * IOIOIO CO COCO CO IO>O1OIO 10 i -3--5 -c fll r>t~e>eocot- CO C410rH 'JO ^1000 9 COCN rHTfOO H O f * CN H OiHCOCN < Tl" CO O4 CO CO rH lOiOiOCOt 1~ i cocp-H SoOOO s C"3 OOO400 " OOOOO C f-t-oo r 5 COOO 4 CNCO O4O4 CN CO O4 COCNO4 CNCO-* O4O4 O4 co O4 IOCOCO CO CNCN cococo 00 CN CD OO>t-CO 00000000 00 -o d'^ a g 0> -*^ a. tNCOOOOOCN rHrHCNCNlO-* 8 ooooo OOr-lF-l O OOO-* OOO4CN C -t CNCN g CD CNCN oooco B CO CO 00 OCOOCO OOrHrHO z -M aj o3 ">1 CO CO CO CO CO CO CO CO'*-* co COCO-* - * 1OCD CD IQCOCO CO ooo -*IO>010 >o WCt-rHrHt^ 1-H OrHlO 04 O iH 00 < O OO 10 t-ioo t^ -CN04 CO COC0U3CN CN l'fli CO CO CO O h-OOO 00 **>' 5 t^ 00 GO 00 IO1O 1O1O lllyl coxo-mo-i < ioo CO ^OCN 3 coco H COrHCO CO iHIOCO CD CNIO^-I rH ""^ 4) o' OlOCDCOI>t^ CO O4OO o O4C34FH 3 04O 9 0>Or-l CO CNCN CN O4OOO S i c '^ S* sljjS^ o O II O o o O iO CN o 1O CN SJH Dec. 20 ! 1 M 6 m a r 1 < ' CM 1 CO i 1 ^ d a ! i 1 s i a -> 1 < a t-5 1 C < ip H T. CD 11 ing last ntal ho 23. o 15 m 31 ai m p ai 12 1 l^a &loSg 216 METABOLISM DURING WALKING. p CMOS CM CM CM CN 00 CM CO CM 10 US IN 00 CM CO tOCMO OS l^fe 3 w H CM ^SS 00 CN CO CM CM g gas g Sftft CM 88S o co OOOOO CM CM CO 5 I53fi f ,i .1 CN looco O COOOS 00 lOtNCN COOCS X CM CO 00 "1 eag*e ^PMgSv a-- O t* MM g^goM x e r 00 00 t-ocoo 00 t-oor- * t^OOOO 00 f.00t- ** OOOOt- 00 S J3 U.O _, o u 8** "3 c h 4I"O B .n . T 1 s CN CNltcN co ScM CN 85) co t^OOCN t-coeo s? 2S CM >a o 3 o M O OT3 H ^^ 0000 00 10 10 CO to tO CD CO CD co^r- f- t-oooo 00 OS OS OS OS .i-g . e_ ^ -3 x8 jG S C ** - O ,oor^ 00 p CNCNCO CN 8W ^ CO 00 OS CM CO CO 00 OS OS o Nt-t- 2 5& H X^ ] = CMCMCM CN ->3 ^ k? II 1 ^-^ V E. . i CO V i CD * RBI j (L *? >- i T3 1-43 2 1 c feSSSS'Sg I ,5*00 sss 8 CO OS OS CO 00 CO co CO 8183 o OSl-HOO to co to CN OOCM ^ 3"|-*fl i goscs OS GOCi O g |!|g CM CN O! cs Ci OS OS i*SJii .OCO CMO CN IOrH*O CDCNt- o CM 00 00 IOOOO CN 00 &sg a ooot- r^oot- CO OSOSiH CO f2^ 3 *"3 S? g^l-H f* t^OOOO X X OS 00 00 OSOO O^^H H CM CM CM CM a it o. -HI-I -3 41 ^ 3 .cMr- 10 00 CO CM T)- ^HCOCM CO OCO-* CO CMOO H CMrHtO CO s l^lli CM CM CD CN CO IOCS'* OS OS OS s OS III CO 8 ococs OSOCM i OS O 00 CD CO LO 1 1C OS >O CO *Sr. ' g-OSCO X COCMO CN tO OS 00 * lOi-lO 1C CMOO * CMr^CO o S ||l- J .0000 CM IN CO SCOW co CO CO tor CD CMCNIN i oooco COIN'* CM CM CM I CO 2 Os 00 CO rf r~co CO CO CO 1 CNCOO 1 S - 55 co 00 O05-* CO ^5 s COOOO s 00 COO OSCMiO OS CM CO 0> 02" 3 |* id ** i THWT* 4 -U CN to co co CO COt^CO CO O , -g- COrH r~ U5r-ICM co CDt^-* CO CO CO CN OS OOSCO " < CO ^ co OS 111 1 m $ - 3 5 ^* s cotooo CO CO 00 CN CD 0000 OS * r-< CO oooo CM CO 00 s 888 g 00 COO CO.-C 1 OS -^ SjS o ^ 1^""^ s r-(^r-l i-! CM CO CO co 10 10 U5 to t-aoao S 00 OS OS 00 j - 1 ll-t 1-1 ^ .i^ .< o COOS M O5i-HO o OOSO CSf-CN CO OOQOt^ 00 COrHO 10 ~ S8 S ol |to CO 5!** 9 O'HrH to OOO-- i tOOSO X CO CM-*-* s - iS"? BIO 1-1 co CO CO IO tO cOcot CO CCt-CN CN O'HO t-tOTH 08 BjS as ^A OS OS veoco Os CO $3$ o lOtOtO o OCMCO OOCNCO e 1: : : s -ols-S M (X fl CO 10 CO a CN OS s 51 ill * g>--9 in CD s CO l"3a I s - CO os r-IIO C Average . 1 Average . 1 Average . r fa Average . 1 Average . . fa Average . . METABOLISM WITH GRADE WALKING. 217 ON-HN t~ NCOCO-* * NO Tf CNCNCN CM IOC! 01 TfOCCO # CN 'CN~H CO CO CO CO co --1O1OJO CO O NNCO s 0000 NN X ri CO CON o CO NOCOO 41 >COiC5l^ t- moo t^ ooo *C t^ cot* t* O5O 00 01 NOt* N^ ^ t*eoo> t .... 000000 oc ,.. OOOOt- oo 0000 X t*t-l* t* Nt*COCO *COCDt* IN t-.-*r-IOO m^-i^co la "*S rHOO Si S S8 s INO CM CO 'O OS CN5 a ss t~ co co coco OS t- i-l is Nt* CO 10 a Sooo NOO 00 CO CO >C U) CO CD t* 00 00 t^ 0000 oo 2d 05 OsO <3> 03 OS o> t*t-t* hi OSO3 OS os oo o 00 OS OS 0> -*~4CON COCO TH r* <-< t*00 -100OS CO So-s 5 toco S t-OSN -lNCO CO N g (N N CM CM CM CM CM CM N * * 9 5 9 * !! n< 8 * co oo com t*osr*oo * CO CO^COrH 00-* CO CO S5; >O CO 00 oor-oo M TflTjt OCO CD co 8N CO 'O OS-HCO l-lt*t* s SN-S CO 00 Nr-l 8 t*O3O CO^N 5 t*r*coco t- t*. 00 OS OS oo we ^^lr-1 rH ^C(N rt ^rH ^H 000000 00 I,-IO p-i NN CM OSO-H O O5 o CTi 1^ CD s CM CM 00 Oi CO N OJI-U5-* O5--1OSO a IOCONO OCOOOOO COCO OS CO *ior- OOSO 8 CNOO coco CO TjHOOO ^ OS O 00 t^ *O>'-1 co-* oo IN co -ico O-* oo # COOCD Osl>rji O f- ocost^oo 03 OSOSOO O-H J COCNCO co (NCO CO NN CM OS OS OS OS NN^ CM coco co O^-iN rH 1-1 OOCOt^r-1 00 N'l'OOO ^< -*!N 00 oo^co o O CO CD ** H CO CO OS OS NON CO -HO CD OCON CO OSCOtNO r^o-^co li-iOO 2 CO CO CO CO OOlNI^r^ rtNCOCO i oco CO O Tjl IO CO CD * IN 00 00 OOCO I- CD CD 8 CD OS.-H CO 00 COl^ O r^ ** NO COCO OS ro CO ^* o ^ O -^ CO i-iNN OS CN COt*-* t^osco OOO 00 CD 'O 8O T-l t*t* t^ 00 00 CO CMTj COCO CO 10 co CO ^J* O co CN * ost^- O3CN * co * r^os Or-l ** co rl< 111 CM s r*-*i-i cot*o CO CO CO < CD CO if i -ITfO CM CO CO co co co 00 CO CO 1O Osb- CON CO-H-* OOSOO 1-1 1~ COO Tt< co NN OOO CM OS -IOCS CO OOO t^ OOO OS t-HNOO a NO t*00 CD ^ cot^O cooo * CO THUJTH-* * On '-TO IO OCO >0 t-coco t^ COt* CD cot- co rjtTHUS CO CO "I CO COCO CO OOCO o OS CO CO lO 10 *COOO 00 oo o CM 00 CM * COOS OC coco co OSO-H co OS CO CD r* NT* CO Tjn-aj S 93 * TJ< ^* COCO OS f ss^ o t OOO 1-1 N-*00 CD .-HOO 0000 s *->l. CD 0000 oo ooo tNCNN CM OP) INN IN i S OCO CO o OOCS NN--I IN NN CM oooo -HNN OS OCOiO-* 00 COO>t>-N H r~r^ t^ CNOSt>- CO CNN N t*CO CM tf OOCO CM HOOO *0 O CO^fO * !5!5SS! 5 cor-^"5 ^^C o t~os lOO 00 COOCO CO CO CO CD CO iCrt cot^ 00 CD >*OSC<)M s opot^r- 310010 a S--i CO s OS OS OS CO CO CO 00-* COl* t^ f~oO COCO COOCO *** o ^1 t*OOCO OOO ES NN (CCO CM CD COO.-I *oo 5 O O O o si R CO CO o co 8 00 co o 10 co t^ 10 co oo 5 o 8 CO 8 8 8 8 e 10 8 00 ji O-StJ * i, . . J3."a ai O 'S ^* pLj "* V* ~ fl M a ^ ti cST* **'** A a u o ** " *" oooot- 00 oooo 00 000000 00 0000 co t-t- * g a l^a 4 * ~ "3 s M oo co co CO 00 CO g CO CM COCO 5 >" A SJ. So'o'd o r-lr-lO H COIN (N ooo O5 00 0000 00 cS s - -a xg xi 9 c *** M o ^* CO CO CO e . . . c^ r^t^co S 10 CO COCO CD CD ooo 8m coco coco 8 g- EH X-i 1 S.2 ^g 3J Cl ,i pH ,-H ?::: a 1 CM r CM CD M 1 1 S 2 .a w'lOOCO 9 (NlOO IOU3-* S COlO '0 CO COO 00 CO-* Ol coo 00 CO CD OiO 00 CO ~ eg c5.S o'c-i. gr-lO CO 28 s ! : ^^a^^o. 3 M xj .OINCO 00 0^<^ rH cor- 10 0^*0 (. CO US < usr- CO 2 ll^fi ^COCOCO CO IOOOOO g COIN OO 1 331 11 1 CO 00 CO ^o , 'e g- 00 >OO * o, CM .00 (. IN COO 41 00 1- co COO CO * lif^S 44 CO CO CO 1 IOOCN co Op S CO |g CO CO CO CO coco co coco 8 CO (NCO ccoo 00 t-coo co 1000 CM CO 00 o 5 !i"Ps SlOOCN ^(NCOCO 1 Hi i is 1 OCOOl 3 op US ^ IO 23 s ? ^^5 S9SS s 00000 0000 00 s coco O>r-l S eooooo 00 COlO coo a coco CO ^ *"S 2.0 I^Hr-,^ -1 (NtNN (N 1OCO CO 00 OOO 00 ooo 05 0000 00 O ^ gCNCMIN -1 NNCN .3|wio WIN 00 10 IO **C4 CO 100 ^ CO CO ^ t. coco O.H 2 o ? s S"" a WOO fl 1 ** cfl ^H N C) O ** 5 (N IB S* >tCOO CNCMO M 0>rf (N CO 00^ CO (30*-* 10 t-0 00 |10105 o t--t^t^ Ol COCO S S3? 99 9 s 1 o 3 : : i 3 n 1 . . in y s iflit ^- CO a CO 8 (N 8 co 8 M 00 o CO : 1.0 CQ o : i fa B fa 1 1 Average . . i 1 2 fcl u o fa Average . . METABOLISM WITH GRADE WALKING. 219 NO _ I-N * !"HO 00 OSrHOCO 10 NTX-*N CO NN N t-00^000 4) *0 50 oo + -HO3 CON o co rH OS CON o CO NO COCO CONCOO CO CO CO CO 10 to ifliO to ^Ot-OSCOW 1* <* ^ t-10 o r-t- N t-00 l-t- t> ot-t-t- *" t-t-t-t- t- ^ oo to oo o >ON COi-H s ION rHOO COlO -HO 5 NOOT)t- t- NN CM NN N cSS So rHN 0000 CO NN 0000 N 00 COCONCO co t-OSrHCO coco^-* CO oo coco to co CO CO CO CO CO CO ts 10-* t-t- iO oo CM to g I CM 5O M i H CM 5O N 9 So 50 OSO co Ot- 3 SffSiS g COOCOi-H cot-oot- OOO NCO OSIOrHOSON r-iCOIOOOOt- 15 NrH 05 00 rH coco IO o i-HN rH OrH H OrH rH t-t-t-00 K 00000000 CO 0000 00 00 00 00 00 00 00 00 ** * coco CO H rH OS OS OS OS CM CO N 5JN " 1 lOCO I-H 00 8& co COOOOrH t-O3OCO I NOSNO IOOOOO3 CO t-OS 00 CO>Ot-OOOOS to 10-* s Soo NCO N NN N NN CM 00 CO 00 OS 00 OSOSOOs OS Osos OS OS OS OSO CSO3 OS 10 IO IO ** -# rHtO OO t-co OS 1 00 00 ON Oco IOIO oo 50 to co OS CO TJH tO 00 iO N . . ii NOB 10 CO oo 1 50 OT*< t-O> NN 0503 cot- N CO N COO 00 NCO CO OO^OOO CO t-OOrHO 00 t-t- t- 00 00 OS OS rHCO rH NO o; OSIO t> So o 8 ss CO 50 IOIO OO $$%% % OOO3OO ? $$ * OOOOOOOS005 5 coo ss o iO 50 rH t. OS TtHO 10 rHON- IO i-iNlOO N l~ rH NNCOCOlOt- IO >OO5 N rHt- os g s COI- too 5D to 0000 oo 8 9 S N S iO IOIO US^S** 10 COO N to IOU3 o o o o OS 8 co 10 co 10 o co OS 8 iO 8 N 1 :: 00 rH i to < 5O a 1 Average | 60 Bj si to Si I 1 o 1 8 ! I < a X Average | 60 00 g i V > J ^ Average | 61 m m o! E to Sl* S.S'o*' 220 METABOLISM DURING WALKING. o g.i . r) T"*0 ** ^, * 1C CDO NOS-* 00 "5 -g o" X s. e^a"" 3 .CO-* "5 P.COCOCO a CO CO CO co CO ONN CO COCO N CO CO CO CO S CO 1C 1C hj _a JH*i a'li*!L "oooot^ 00 oooos r-NN co MO 1C CO CO CO OS J3 siisi ^n s x *-3 fe j? a n O ^ o ""* CO or^to '- CO C01"* -* E to > e o s~ ,-. "3 c .CD COW p C3O3O * s co OOi-iO co co co 2 osoor- s t^ric CONN g OS Oe8-oa 3 -g ^ ""^^ ^ -lr-lrH 1-1 i-4rHp-l 1-1 1 'C "8 ' Q ^ j? X Q ^OiNN a ass s s 8 2^2 s COlCW S < q 2 S 1 ^ tj ^ C 1C os 1C s I 5 i|a|il g^.^.^ * ^^^ ."* CO CO CO co CO COCO CO NNN N K a s |fe]bl + i\\\ S a CD i : : : ods of experin CQ' 5 ^x ^ 'TJ -*J vx ^ o g^ X S CD 1C .t^OOOO ONNN os OS CO CO t^oooC' INNN OS oo IN OSNOS 00 1C CO -INN NNN IN M N CO CO CO NINN 1C 1C IN 00-* 00 O OS 1C Co S3 .Si la 53 m-S5 ^^ PJ-J O ^i .. ^SSf2 g COON S NNO 1C CD CO s iCCDlfl OS OS OS 1C OS * i. a> d^( |^TH^ * ^"^ * CO CO CO co NCNr-l N S . 4) g g 1- ^.wieD i^-INrH 00 *coo IN OOOO CO **r-oo co CO -.10 t. _Q 3 t> C3 j- -g s llpll |$ s !S5!5 1C CD 1C CO CO CO 10 co OOOS OSOOS CO ^ CO OS CO *" g 3o 900 g"S co^n CDlCCN NNO 00 1C 00 00 41 CO--HU5 ^ pi - -ag| Qj i"*" ^ ;55!S to 1C CD CD CO CO CO 'O co 958 83S OS CO "o o* u .2^ laS V s 1 o B. . . . 1 . . . O O N N 03 day. See li ments per b walking of ~ "S'S'g^.a to CD OS >-i o 1 s | to CJ bC ca E OJ > 00 B CD O I iH a to 1 E ui a CO CD M I CD K l Average for the 2 Average of incre speed of horizontal METABOLISM WITH GRADE WALKING. 221 II | Si X * 3 ft ri ~OO> >Ot>.TlO OOCOtOOn-!N fi . O to ! oo -H o *o rH 03 oo co o> *o *4t o> o rH t- -H CD O CO O) ^J* OS O CN O t-OOOOO> O> 1O1OO COCO d si: i : o : : pr-oo o >O (MNrH rH r^NN ^COO < P'^! < P ( P "? "OO5O1 lOrH CO Ot^NrOOlO r-l t-00 t-Oi-lN t- tt^00 -<1IIO O OOOOSNN^" O .^JiHi I NCOCOCO CO r-lf-lrH rHrH CN r- 1 1 < r-l N CN 04 N COCO Oil Ir-ICO 00 IO i I 00 ^1 O> 00 CO rH CO i I 00 CO rH .O^rH 1 1 1^ O O CO O-JCOt^ N O? t** 00 1** r-l O CO 1 I N CSCOOO COrHlOOO rH CO CD 00 CO ^* OJ O CO CD 00 r-l CO 00 4i r-l rH ^IIO*OIO l* CO CO CO r-l F-* N CO CO CO CO ^ ^ CO Soj oiooOrH co Opco wt oo cot^O'-icoo) o O O O O 1 I O OOO 1 I rH O O O rH rH rH rH ( oj,_i,_i oocooqio o T)-fd M -*j *j +j -w> . -*j tr* . +j - . -u +i +^ *j *j HU . *j CJ CO tO .OCOt^t^* .CD . *O CO CO 5*01*" o^ . *O CO CO t^ t^ 00 .*Q iJMi a cr-rs 8| i B*i *|RPJ 1 CQ Oi-< co 222 METABOLISM DURING WALKING. I & S a > ~ l ~-*OCOCOO> N^l(DO> 00 t-r-IOS-*tx.U5COt US A S J *i >f ffi g W M IN O50000t>-^O it) lO (OtOiO>O NUHlMlin IN C^ - OOf-CMtOt^CO>Ocp "5 ^ CO CO "^* ^* **J* ^ ^* 'V CO "S >^'CcS S'4 ,-i o.b o 55 ,-~ -13.^ ^OSM^tOOOO WN^HNCOINO OOrHrH O> rHCO"3r-IO>r-(rHO 3 I -? gi J6S g. e< 8ffi n fet o a goSb * 1- oo oo oo oo oo co O5 O3 o> os os oj aoososos i * CD to iO lO ^ 10 i.O 10 CO 1 llva* ^ * o 2 fl 'S e -2 ^rt. t^OOC5t>-i-H^l (N-*CO Se^tDOS-^WO NtOr-(COP500(N O3>O*O OS OOOOOO?t>.(NO ^1 CM r-t>-i>ooooasf-!r-< o 1 g S^S o * 5 . HH 00 B ST3 H " "MMM^OIO ^rjtioiowwt^ OeO-*i-it"- oo--(O3t^ ^ CO (N m rH * 2 IO O O * r-( t- rH 00 CO O t^ t^ OO OS OS O COOSOO IN CM CO CO CO CO CO ** * & 2 a! fr^'S ic-^mooos t^ o * O 1 rS-s.3 j O T-l s &g t^coor-toco r-i>.oO"*ct^os eot^co-* tt) oo * o r* OO -*r-i^Hio .OSO^HINlOlO ^-((NCO-*tC>t^OS TjKOOSrH IN N 00 CM IN (N O CO O -H "5 f- OO CO CO * O ^ ic>ocio*ocoi>r oo 03 ts -6 cu a. a s in s& lijiji] jjjljij \\\\ S 8 :::::: 5; r-l r-lrH rl r ood, grou Contin -3 S22 s as Q JjS o flCOr^OSi-l i-< O U3 O rH IM t -*C3SOO 2 N OiO l^ CO *-** 10 1- 00 00 O r-l rH r-l rH r-l rH rH r-l rH N 1 . . o5t~rcooo o oo r- 1>- 1~- os o i* i-ii-io U5 * IN O rH rH rH -H O O | a. W m.2-2 S3 2 ** ^t^t^OOOi-i OOOBOCO>OiOO CO-*OOO NIMININCOCO (N IM CO CO CO CO * COCOCO-* rH OS O O rH CM CO * rrt CO (N rHINNINiNCNININ CN -*Si gOCOCOCOCOO O CO "3 OS CO OS r-l lOOSCON O IN 10 O CO IN >O 00 00 U5 8 S |1I . IH * OS t~ N CO * * OS (N as ^^ rj< o --H c^ CO CO ^^ CD CO 00 -^ O CO (N -^ OS SlCCOINr-COCOCOO C33 r-HN-*lOCOaS--HCo osoo^o t-t-corjiasoosos e it t^>Ogs-*Or-l OSCOlNt^NNiO COCOOCO OsOOi-HCMN OS O i-t rl tN CM IN Oi-llN( Tjl t- O TH CO >O OS rH t- 1- 00 00 00 OS OS O rH - i8"S n 00 * IN * O 5 (NCOCN-*r-OSiO COCOOSiO t 00 1- CO * "5 1- !> rH OS If -2 fl^ BfJ 5cOt>.O!OO5O N.Ot^COOOCOO5 tNt^CO-H v "5 "O CO cOt" 00 <* O "5 CO - OS 00 rH 00 CO CO "5 CO lO CD CO W*-*iOiOcOC^t 1O ylism dun si ^'S ^a o S> >OcOCOt"0000 IO iO CO CO t- 1> 00 >Q(Ot^ .. oooooo. .0000000. . oooo ^^i****^** 3 * 3 * 3 ^ 4a*34*4343+.^34a^4a {? dO^OOO^OO o i.*: O 'O O 'O O iO OO^O^OO . to 10 co cor- oo .Tnoic- .loocor- a a & 5 O 1O "- 1 tN CN . S 3SS32SS3 3 CQ o oooaJdJ^va) a> s essssssa a Q O OiOOiOOOOO O H ^ -rJl^LOOcDt-t^oO CO jvj"O OOOOJOOO"2 iOiOO'OOiOi'5O'O iO ^co oco-*-*>oiocot^r- ^10 * a os CN >O 00 METABOLISM WITH GRADE WALKING. 223 CO **< OS 000 CO COt- t-W-H.OXOS.HO o^o-^ococo IOCMOSUSCO^^I t--ooco> t-THf, 00 COt* --<*<< N CD N N N N cococococococococo CO CO CO CO CO CO CO CO CO ^< CO CM I-H OS t>- CO CO CO CO CON CM T-H Ol Ol O^ C^ Ci O5 CONNWWWW i-lCMOOOOOS CO CO CO CO CO CO N sss S8S & ^OOW.H.Q.HNCON *,<. iQe i-t OS .-< PJ CO O >O ^.OOOOSOO^ ^^oOt-r-0> osoe* OSON t-xx t-0000 00 COrH^OUSrHCMOSO O U5 O -" CO CO OS OS ioooasoccNcot^!-! ss^ssg SggSgg* 00 I s * CD O CP*O O> xoo CO CO CO XNrH 00 iHrHtHNNNcococo (NNNCO^^^US coco ^* *o cot t *iOCOf-XXOS lOOt^OOOOOlO t-OSO "^a OS ss8838oi3 SOI t^ CO N Tj* r- CO OS r 1 ^ CO OS O 00 CO ' CN CO CN CO O * I Ht-cOCOXX-* O fN O CC O O CO 8t^Or-HOQ^C4 OS t C30 Co co co rt< * 1C to tD t^ t^ 00 lOlOCOXXOr-l t^ 00 00 OS -< N (N CO 00 O> O i-* W CO OS CM CO NCOlO C4 X^TjllOCOOSOSXX XXXXXXXXX 00 OS CO CO COCO N. 00 X XX 00 0000 lOIOTfi-IOO'HX XXX OS XOS X CM OS 00 OS -H N IO XXX XOS OS OS CO 00 CO GO Oi O5 Ol XOSOS OS OS OS OS M"coxoxt Ncot- XOOQOCO-HiOCO t-XXOrHr-iCNCOCO rtl-ILO 1 Tl CO I-l ^- 1 OsOOCO-*>OCOt~ 1-HCOXiOOOlO >O t CD X <-< Ol IN O--O'-'i-l r- 0! CO OS N * * 00 OOXOSOCNCOCO'* X OS i-i ^ O Oi O CO CO * CM CO CO "5 Of X^^-.NCCO iO C33 CO iO g O 00 CMt^t- sss CO COO OS -HrHrHrH NNCO IN .2 ??:!:: i & ;s ;;;;; 5SS2s:s ?38$SS^S N Sis' s t-t-xxt-r- CO CO CO CO COCO Xf-t~xi^t-x COCO CO CO CO CO CO ??? wt-x CO CO CO CO CO DO J3 CO rnOCOCSXCO OS O rH 1-1 1-1 N 00-ilOO' lt^*O^* OOrHCCCOCNCNCO SCO CO IN IN iOoO>o -Oeo -^ TT io -r* t CO CO I 1 CO 1C 1C CD ^Sf: coxeo cot-x O >OCOt-(Nt^lO0 -HCOU5COX.HIO 0 10 O CN CM W CO CO * * s?S;5^s COOCO-^OSiO--! CO-*Ttc*TJ(lOCO O-*rH *IOCO CON-* lOt-X 28 t 1 lONCOCOCsX-'l't-lO N>OWt-Os^iOCO (N^^^rHO!^ XeOt-Xcor-cO CO CD O CO CO rH CO t-COrH cowo 00 i N N N N N N N N N co co >o co >a eo 10 co CNMNINCNCNINCN CO CO Tt< IO CO >O X NCNNCNCNCNCN CO CM ^ CO t- -xo)O CN CM CM CM CM CM CO &SS OrHIO CO CO CO O CO 5 t-.OTft-.OOOS COW (Nl-^tNiOtOCOO TtOC-OSTIO CO t- X OS O r-< -< CO CC CO CO O "^ *H t* XOSO rH CNCO t-COCg COOO OS IN CO ^ co co NCO>O CO * t-fHt- -THlOrHlO tO N CO * CD OS IH i-H TK.Of.Wr-, OS OS OS OS CO CO X OS rH COCOCMO-*5X ocoos OrHT( 00 t-rHco -.Of-N^n t-XX -ClOiCO {^tXXOsOOO t CM 00 i-i CO OS i-i t-XXOOOr-l * 5 CO f- T*< CO X XXOSOSOOO COOXXCOXO XOSOSOSOOrH CD CO CM O5OO lOrHCO OSOO rHrH WWNCON.O.OCON CNX^COOOX^CO rJ-N^^oslOX U9 CO CO OS COW lOOOCDCOCM'*-* occo^ XrHN CO lOiHt-t^NCOOXO co-*TinncoeOt-l-X OOCOCOXCDCOlO--! eOTH^nocot>t-w eoriioeot-t-X CMCCT)O CO CO t~ t X & 6 6 C 6 8 IEEEEES iOOiOO"OO>O ^f iO iO CO CO t* t '23S2S 45 to 50 meters. . . . 55 to 60 meters. . . . 60 to 65 meters. . . . 50 to 55 meters' . . . 55 to 60 meters. . . . 65 to 70 meters . . . 40 to 45 meters. . . . 224 METABOLISM DURING WALKING. CARBON-DIOXIDE ELIMINATION AND OXYGEN CONSUMPTION DURING GRADE WALKING. The total carbon dioxide eliminated and oxygen consumed during the grade-walking experiments, as given chronologically in tables 13 to 16, show variations for the different periods of the individual days, but when we take into consideration the fact that the speed also varied to a certain extent for the different periods on each day, these variations hi the carbon dioxide and oxygen appear to have no general significance, especially as they have no uniform relationship with the variations in the speed. On the other hand, when the data are grouped according to grade and speed, as is done in table 56, we find with any one grade that when the speed increases, that is, when the work performed in- creases, there is likewise an increase in the carbon dioxide and oxygen. We also find that both the carbon dioxide and oxygen with a low speed and high grade are lower than when the same amount of work is accom- plished with a high speed and a low grade. This is also shown in the curves in figures 16 to 19, which are discussed later. TABLE 57. Metabolism of W. K. and E. D. B., with maximum amount of work performed. (Values per minute.) Subject. Date. Work performed. Carbon dioxide. Oxygen. Increase over stand- ing requirement. Carbon dioxide. Oxygen. W. K.. June 23, 1915 Feb. 22,1916 Mar. 6,1912* May 10, 1914 s kg.m. !891 !1,569 1,024 c. c. 2,152 3,017 2,751 2,101 c. c. 2,094 3,132 2,976 ,2,384 p. ct. 1,057 1,416 1,180 877 p. ct. 818 1,205 1,110 869 E. D. B. M. A. M 'Work due to grade-lift. See column /, tables 54 and 55. *See Benedict and Cathcart, Carnegie Inst. Wash. Pub. No. 187, 1913, p. 64, table 74, and p. 124, table 116. The subject rode a bicycle ergometer. 3 See Benedict and Murschhauser, Carnegie Inst. Wash. Pub. No. 231, 1915, p. 59. Standing values for same day for carbon dioxide and oxygen (215 c. c. and 246 c. c., respectively) used as base for computing increase for this period, also for March 6, 1912. The subject walked on a level. The maximum daily averages for the two subjects who did the largest amounts of work (W. K. and E. D. B.) are given in table 57. For comparison, the maximum performance of M. A. M. on a bicycle ergometer in the study of Benedict and Cathcart, 1 and of the same subject walking on a level in the study of Benedict and Murschhauser 2 are included in the table. It should be stated, however, that whereas the values for W. K. and E. D. B. represent an average of data ob- tained in two periods of approximately 10 minutes each, the figures for 'Benedict and Cathcart, Carnegie Inst. Wash. Pub. No. 187, 1913, p. 64, table 74, and p. 124, table 116. 'Benedict and Murschhauser, Carnegie Inst. Wash. Pub. No. 231, 1915, p. 59. METABOLISM WITH GRADE WALKING. 225 M. A. M. in both cases represent measurements in only one period of the same length. By comparing these maximum values with the average standing requirements for the two subjects W. K. and E. D. B. (see tables 5 and 6, pp. 44 and 46), we find a percentage increase in the carbon-dioxide elimination and oxygen consumption of 1,057 and 818 per cent, respectively, for W. K., and 1,416 and 1,205 per cent, respectively, for E. D. B. In figures 16 and 17 the total carbon-dioxide production per minute versus the kilogrammeters of work is plotted for the different grades for four of the subjects. From these curves it may be seen that the car- bon-dioxide production per minute for all of the subjects increased uniformly with the increase in the amount of work performed. With both W. K. and E. D. B. the curves for the various grades show a general parallelism. The significant feature of these curves is, however, their relative position, in that the curve for the higher grade always CO 2 c. c. 2200 2000 1800 1600 1400 1200 1000 800 600 f / / / jz . / // //, j/! / '/. y/ * TKH. 10.0* e RR.R. 10:0 * 15.0 * W.K. 3.6^.9 o 10.0 15.0 20.0 V 25.0 ' CD B X** MKOB V Ml , ? ra o ,* wx-o EJXB/-a 00 Kg.ms. 200 400 600 800 1200 1400 1600 FIG. 20. Respiratory quotients of W. K. and E. D. B. referred to kilogrammeters of work performed in grade walking. (Val- ues per minute from table 56.) The respiratory quotient of the normal subject in the post-absorp- tive condition is not far from 0.82 to 0.85, and from our measurements of the transition requirements (see p. 296), it would appear that the oxygen consumption and ventilation reached cons tancyl within 2|or 3 minutes after the change from rest to work. As the subject walked 5 to 10 or more minutes previous to each period, it is therefore believed that before the period began the carbon dioxide and oxygen had become constant at the rate demanded by the work, and that the respiratory quotient would be of the average normal value unless an alteration in the character of the metabolism bad taken place. It is seen in table 56 (p. 221) that the average respiratory quotient for the different subjects was not different from the normal standing average for the lower grades and speeds, 0.87 being the highest average value found for any of the subjects below a 10 per cent grade at 60^to METABOLISM WITH GRADE WALKING. 231 65 meters per minute (about 2.5 miles an hour). It may also be seen that the respiratory quotient tended to increase as the grade and speed increased. This is more apparent in figure 20, in which the respiratory quotients for W. K. and E. D. B. given in table 56 have been plotted for experiments with varying degrees of work. In this chart the majority of the respiratory quotients up to approximately 600 kg. m. of work fall within the limits of 0.80 to 0.87, i. e., the normal post- absorptive respiratory quotients, and for 700 to 1,000 kg. m. of work, almost half of the respiratory quotients are 0.90 or above, while none are below 0.85. For more than 1,100 kg. m. the respiratory quotients are grouped around 0.93 and none are below 0.90, while the two determinations with work greater than 1,300 kg. m. give respi- ratory quotients of 0.97. Figure 20 gives clear indication that for such short periods as these, 600 kg. m. or less of work per minute do not tend to alter the character of the respiratory quotient, but with moder- ately heavy to heavy work, involving over 600 kg. m. per minute, the body alters its metabolism by a tendency to a selective consumption of its carbohydrate reserve. TABLE 60. Comparison of respiratory quotients of E. D. B. during grade walking for the days of the week November 1 to December 11, 1915, (Subject in post-absorptive condition.) Nov. 1 to 6. Nov. 8 to 13. Nov. 15 to 20. Nov. 22 to 27. Nov.29toDec.4. Dec. 6 to 11. Day. Work Respi- Work Respi- Work Respi- Work Respi- Work Respi- Work Respi- due to ratory due to ratory due to ratory due to ratory due to ratory due to ratory grade- quo- grade- quo- grade- quo- grade- quo- grade- quo- grade- quo- lift. tient. lift. tient. lift. tient. lift. tient. lift. tient. lift. tient. kg. m. kg. m. kg. m. kg. m. kg. m. kg. m. Mon. . . 143.5 0.88 155.0 0.89 222 A 0.91 250.5 0.84 387.7 0.86 346.6 0.90 Tues... 120.2 .83 161.1 .83 215.4 .82 337.3 .86 464.4 .87 412.4 .89 Wed... 124.7 .83 163.1 .83 289.9 .84 338.1 .84 474.4 .89 511.2 .83 Thurs 140.7 .82 194.7 .85 0) 403.5 .91 Fri 124.1 .82 192.3 .85 395.9 2 .92 418.9 .89 Sat 141.8 5 .88 217.5 .85 390.1 4 .88 393.7 .88 thanksgiving Day. 2 Rock candy in supper preceding day. 3 Molasses candy in supper preceding day. 4 Candy and nuts in supper preceding day. Zuntz and Schumburg 1 and Durig 2 have stated that work pro- longed over a series of days tends to reduce the carbohydrate store in the body with a simultaneous lowering of the respiratory quotient and that a rest of one day in three is desirable in order to maintain a normal quotient. Contrary to the results of these authors, an inspection of the respiratory quotients for W. K. shows no evidence of a tendency for the quotient to decrease on successive days of walking with a subse- quent increase on the omission of an experimental day. With E. D. B. *Zuntz and Schumburg, Physiologic des Marsches, Berlin, 1901, p. 258. 2 Durig, Arch. f. d. ges. Physiol., 1906, 113, p. 263. 232 METABOLISM DURING WALKING. the quotients in the first few weeks of the series (in the untrained period) usually show higher values for the experiments on Mondays which followed the day of rest on Sunday. (See table 60.) Later in the study, and especially when the work became more intense, this is not apparent, for the later quotients follow no general trend, but are all on a higher level than those when the work of walking was lighter. With this subject it is possible that during the intermission on Sunday there was an accumulation of carbohydrate in the body which was drawn upon during the walking of Monday, thus raising the quotient for that day. If this were the case, the increase in the body carbo- hydrate appears to have been insufficient to supply the energy re- quired to keep it at this higher level on the following days; accordingly there was a subsequent return of the quotient to the previous value. That no difference in the Monday quotients is apparent when the amount of walking became greater may be explained by saying that the increase in the metabolism due to the increase in the work may have been so large that this minor factor was lost sight of. Since our sub- jects were uncontrolled outside of the Laboratory, and, aside from the data regarding the last meal before the experiment, no detailed record was made of the diet, it is possible that the higher quotients on Monday have no special significance in this connection, except to show that some change in diet was made of which we have no knowledge, such as a possible indulgence in candy on the day of rest. The absence of definite evidence in our results of the influence of a day of rest, as compared with the results found by the investigators referred to, may be due to a difference in the character of the experi- ments. With Zuntz and Schumburg the subject was carrying a load of approximately 25 kg. 1 while walking on a level at rates from 70 to 80 meters per minute. This does not allow a statement in terms of kilogrammeters, but the oxygen consumption was no greater nor as large, in many instances, as found for the subjects W. K. and E. D. B., who were walking up-grade without a load. Then' subjects were con- trolled in their diet, while ours, as stated, were unrestrained, except for a 12-hour abstinence from food preceding the experiment. Evi- dently with W. K., and possibly with E. D. B., the work performed on these days was not such as to reduce the store of body carbohydrate to so great an extent that it could not be restored to a normal level during the resting hours of the remainder of the day and night. After the writing of this report had been practically completed, the most interesting paper of Krogh and Lindhard, 2 entitled "The relative value of fat and carbohydrate as sources of muscular energy, with appendices on the correlation between standard metabolism and the respiratory quotient during resb and work," was received. The experi- *Zuntz and Schumburg, Physiologie des Marsches, Berlin, 1901, p. 249. *Krogh and Lindhard, Biochem. Journ., 1920, 14, p. 290. METABOLISM WITH GRADE WALKING. 233 ence of the Nutrition Laboratory is wholly in line with their question- ing the use of the mouthpiece in researches involving specifically a study of the respiratory quotient. Benedict and Murschhauser 1 emphasized the desirability of studying the metabolism during muscu- lar work in a respiration chamber "with free breathing, without the use of either mouth or nose appliances." This Krogh and Lindhard have done with all of the niceties of detail characterizing Krogh's work. It is a cause for regret that since they stress especially the respiratory quotient as affected by muscular work, they did not include at least a few experiments with an oxygen consumption of from 1,500 to 3,000 c. c. per minute, as it was especially in regard to these periods of severe work that Benedict and Murschhauser made their recommendations as to method of study. Indeed, the results given in this present re- port (see table 56, p. 221) show high respiratory quotients, which, in the absence of demonstrated technical or physiological error, lead only to the conclusion that there is a specific, selective carbohydrate com- bustion with this intensity of performance. TOTAL HEAT-OTJTPUT DURING GRADE WALKING. The total heat expended per minute during grade walking is given in tables 13 to 16, and also in column j, tables 52 to 55, and indicates the range of requirements for men of different weights at different grades and speeds. As the amount of heat produced is conditioned upon the work accomplished per minute, no direct comparison can be made except on the basis of kilogrammeters of work performed. These values, computed from the body-weight and grade-lift, are given in column / of tables 52 to 55. The range in the total amounts of heat developed during grade walking is limited hi the case of the two subjects, T. H. H. and H. R. R., as they dropped out of the study before any severe amount of work was per- formed. The range for W. K. is from 3.72 to 10.57 calories, with approximately 125 to 900 kg. m. of work, and for E. D. B. from 2.59 to 15.65 calories for work ranging from 59 to 1,569 kg. m. per minute. This last value is the average of two periods on February 22, when the subject walked up a 40 per cent grade at a rate of 65.2 meters per minute (2.50 miles an hour). The first period was of 10 minutes dura- tion, with 13 minutes of preliminary walking. At the close of the period, the subject complained of pains in his chest and was doubtful of his ability to perform a second period of similar activity. The dura- tion of the last period was reduced to 6 minutes after a preliminary walk of 5 minutes, as the subject showed signs of exhaustion. If the values for the total heat-output per minute are plotted on the basis of kilogrammeters of work, as is done in figures 21 and 22, it is seen that the total heat-output is a linear function of the work performed for each Benedict and Murschhauser, Carnegie Inst. Wash. Pub. No. 231, 1915, p. 30. 234 METABOLISM DURING WALKING. grade. It appears from the relative positions of the curves for W. K. that the total heat produced for a given amount of work is somewhat higher when the work is performed at a fast rate of walking with a low grade. For instance, with 400 kg. m. of work on a 15 per cent grade, the total heat-output would be 5.62 calories, while with the same 3 5 kg.Tns! 300 500 700 ^00 FIG. 21. Total heat-output of W. K., referred to kilo- grammeters of work performed in walking on dif- ferent grades. (Values per minute.) 15.5 14.5 13.5 12.5 11.5 10.5 9.5 8.5 7.5 6.5 5.5 4.5 3.5 2.5 Kg / / / / A / / ^ y / '% 7 // x > Y // 'S A o /" /, / -;.- [12 1:1 c o-c a M.S. X ^ X^ o 300 500 700 90 IDS. Fio. 23. Total oxygen consumption and heat-produc- tion of W. K., referred to kilogrammeters of work performed in grade walking. (Values per minute from table 56.) METABOLISM WITH GRADE WALKING. 237 o, O.C. 3100 2900 2700 2500 2300 .2100 1900 1700 1500 1300 1100 900 700 500 300 Kg. ^ Cals. 16.0 14.0 12.0 10.0 8.0 6.0 4.0 2.0 30 / x ^x ' X X oc ILS. X / 5^ r -X ^ " ^ ^ f / . 5^% ^" '/ . 0^ ^ x-"^ / " ^ v> ^> ^^ -r , X fiiT" J "1j > ., ^ *-** ms. 200 400 600 800 1000 1200 1400 16 r\y.iit9. f.\j\> TW \j\j-u ww iwv iww itw luuvj FIG. 24. Total oxygen consumption and heat-production of E. D. B., referred to kilogrammeters of work performed in grade walking. (Val- ues per minute from table 56.) requirement of E. D. B., as was done in considering the curve for the oxygen consumption given in the same figure (see p. 228), we find his requirement for maintenance, horizontal component, step-lift, etc., to be 2.00 calories, and superimposed on this is the average requirement of 8.7 gram-calories for each kilogrammeter of work due to grade-lift. Since the curve for W. K. is not linear throughout, no definite estimate can be made for his basal requirement, but the slope of the line above 400 kg. m. would indicate that the requirement for each kilogrammeter of work due to grade-lift was 10.5 gram-calories. The total heat-output as estimated from the curves in figures 23 and 24 for increasing amounts of work, also the increase over the stand- ing requirements due to the work performed, are recorded in tables 63 and 64. It is seen in comparing these sets of figures, as was done with tables 58 and 59, that of the two subjects W. K. spent the larger amount of heat over the standing requirement for a given amount of work, and also that the heat expended per unit of 100 kg. m. in excess of the standing requirement was greater for small than for large amounts of work. In both cases the increment in the heat per 100 kg. m. decreased rapidly, approximating a value of 1.10 calories for W. K. and 0.96 cal- orie for E. D. B. for 800 to 900 kg. m., while for 1,500 to 1,600 kg. m. the value for E. D. B. was slightly less, i. e., 0.92 calorie. 238 METABOLISM DURING WALKING. TABLE 63. Total heat-output of W. K., with increasing amounts of work, in grade-walking experiments without food, (Values per minute.) 1 Increase over stand- Percentage increase ing requirement. over standing Kg. m. of work Heat- (1.10 cals.) requirement. done. output. Total Per 100 kg. m. Total. Per 100 kg. m. cals. cals. cals. p. ct. p. ct. 100 3.35 2.25 2.25 205 205 200 4.10 3.00 1.50 273 137 300 4.95 3.85 1.28 350 116 400 5.80 4.70 1.18 427 107 500 6.90 5.80 1.16 527 105 600 7.90 6.80 1.13 618 103 700 9.00 7.90 1.13 718 103 800 10.00 8.90 1.11 809 101 900 11.00 9.90 1.10 900 100 Estimated from curve in figure 23. TABLE 64. Total heat-output of E. D. B., with increasing amounts of work, in grade-walking experiments without food. (Values per minute.) 1 Increase over stand- Percentage increase ing requirement. over standing Kg. m. of work Heat- (1.16 cals.) requirement. done. output. Total Per 100 kg. m. Total. Per 100 kg. m. cals. cals. cals. p. ct. p. ct. 100 2.85 1.69 1.69 146 146 200 3.70 2.54 1.27 219 110 300 4.60 3.44 1.15 297 99 400 5.50 4.34 1.09 374 94 500 6.35 5.19 1.04 447 89 600 7.25 6.09 1.02 525 88 700 8.10 6.94 .99 598 85 800 8.95 7.79 .97 672 84 900 9.80 8.64 .96 745 83 1,000 10.70 9.54 .95 822 82 1,100 11.60 10.44 .95 900 82 1,200 12.45 11.29 .94 973 81 1,300 13.30 12.14 .93 1,047 80 1,400 14.20 13.04 .93 1,124 80 1,500 15.05 13.89 .93 1,197 80 1,600 15.90 14.74 .92 1,271 79 Estimated from curve in figure 24. INCREMENT IN HEAT-OUTPUT DUE TO GRADE-LIFT. TOTAL INCREMENT IN HEAT DUE TO GRADE-LIFT. That portion of the total heat expended during grade walking that is due to the grade per se is the total heat-output less the energy re- quirements for standing and horizontal walking. This difference is METABOLISM WITH GRADE WALKING. 239 Cals. 13.0 r Gala. 8.0 /- & -3^ iao 7.0 6.0 5.0 4.0 3.0 2.0 1.0 joL Kg.ms. 300 500 700 900 FIG. 25. Daily increments in heat-production over standing requirement and horizontal component, referred to kilogrammeters of work done in walking experiments on different grades with W. K. (Val- ues per minute.) 12.0. 11.0. 10.0. 9.0. 8.0. 7.0. 6.0. 5.0. 4.0. 3.0. 2.0. 1.0. Kg.ms. 200 600 800 1000 1200 1400 1600 FIG. 26. Daily increments in heat-production over standing requirement and horizontal component, referred to kilo- grammeters of work done in walking experiments on dif- ferent grades with E. D. B. (Values per minute.) 240 METABOLISM DURING WALKING. recorded in column o of tables 52 to 55. The standing requirements in tables 3 to 7 and the increments due to walking on a level given in tables 29 to 33 are used for obtaining the total requirements for these two factors. The values used for deduction were either determined on the same day or represent an average value, the selections being noted in the footnotes to tables 52 to 55. These increments in the heat-output which are due specifically to the grade have been plotted for W. K. and E. D. B. for each grade on the basis of kilogrammeters of work. (See figs. 25 and 26.) It is seen in these figures that the heat increment is a linear function of the work done, as was the total heat (see figs. 21 and 22), but in these curves, with the basal and horizontal require- ments eliminated, the amounts of heat produced for the same amounts of work with different grades more nearly coincide and the curves as a whole make a more nearly uniform and continuous grouping, thus indi- cating that the heat increment is practically independent of whether the given amount of work is produced by altering the rate of walking or the grade. 4 FIG. 27. Average increments in heat-production due to grade- lift in walking experiments with E. D. B. (Values per min- ute from table 56.) To show the relation between the increment in the heat-output and the grade and speed used in walking, the data for E. D. B. in table 56 have been plotted for the various speeds and grades and the curves given in figure 27. It will be seen from these curves that a change in speed from 35-40 meters to 75-80 meters per minute (or approximately 1.5 to 3 miles per hour) on a 20 per cent grade increased the heat-output due to the grade walking approximately 4.5 calories, while a change from a 5 per cent grade to a 20 per cent grade increased this factor METABOLISM WITH GRADE WALKING. 241 about 2.25 calories when E. D. B. walked at 35 to 40 meters per minute, and about 6.25 calories when he walked at 75 to 80 meters per minute. These changes may be calculated on a percentage basis by referring to the values in column m of table 56 (p. 221). Thus, a change in speed from 35^10 meters per minute to 75-80 meters per minute increased the heat-output over that requited for standing and the horizontal com- ponent 0.42 calorie, or 60 per cent, with a 5 per cent grade; 1.76 calo- ries, or 108 per cent, with a 10 per cent grade; 2.29 calories, or 92 per cent, with a 15 per cent grade; and 4.30 calories, or 139 per cent, with a 20 per cent grade. When the subject was walking with a speed of 35 to 40 meters and on a 5 per cent grade, the heat-output due to grade walking averaged 0.70 calorie. When he changed to a grade of 10 per cent without change of speed, the heat-output increased 0.93 calorie, or 133 per cent; with a 15 per cent grade, the increase over the 5 per cent value was 1.8 calories, or 257 per cent; and with a 20 per cent grade, 2.39 calories, or 341 per cent. Similarly, when the speed of walking was 75 to 80 meters per minute, the percentage increases over the 5 per cent grade were 203 per cent for the 10 per cent grade, 328 per cent for the 15 per cent grade, 560 per cent for the 20 per cent grade, and 729 per cent for the 25 per cent grade. INCREMENT IN HEAT PER KILOGRAMMETER OP WORK DONE IN GRADE-LIFT. From the increment in the heat-output due to the grade and the total kilogrammeters of work due to the grade-lift, the heat outlay per kilogrammeter of work done in the elevation of the body has been computed and recorded hi column p of tables 52 to 55. A summary of the daily averages is given in table 65. A. J. 0., with only one TABLE 65. Average increment in heat-output due to grade-lift per kilogrammeter of work. No. of Minimum Maximum Average Subject. experi- incre- incre- incre- ments. ment. ment. ment. gm.-cals. gm.-cals. gm.-cals. A. J. O. . . 1 5.6 H. R. R.. 6 7.2 8.0 7.5 T. H. H.. 8 6.8 8.1 7.6 W. K 48 5.3 9.3 8.1 E. D. B... 79 4.8 8.7 7.0 Average . 6.0 8.5 7.2 experiment of two periods, shows the lowest average value, or 5.6 gram-calories. This was for the low grade of 3.6 per cent, with but 172 kg. m. of work. The total heat-output was correspondingly low and the proportionate probability of error on deducting the values for the standing and horizontal walking requirements was naturally large. 242 METABOLISM DURING WALKING. The values for H. R. R. were fairly uniform, averaging 7.5 gram- calories, with a range in work performed of 452 to 717 kg. m. The highest value of 8.0 gram-calories was in the one experiment with a 15 per cent grade. T. H. H. also performed his task at an average energy cost of 7.6 gram-calories, although his daily work did not exceed 392 kg. m. as compared with 717 kg. m. for H. R. R. W. K. on his first day, with a 3.6 per cent grade, did only 131 kg. m. of work, and his low heat cost for this work of 5.3 gram-calories may be assumed as due largely to the difficulty of measuring the heat differ- ences in these small amounts. His maximum cost was 9.3 gram-calo- ries when 719 kg. m. of work were done and the average value 8.1 gram-calories. With E. D. B. the range was wider than for any of the five men. His lowest daily cost per kilogrammeter was 4.8 gram-calories, and a closely approximate value was found on several other days. Although these low values are not necessarily for the period of the least amount of work, in all but one case the work performed was below 200 kg. m. and the heat due to the grade work as computed constitutes approximately but one-fourth of the total heat measured. These low values appear both in the early period of grade walking and again on the last day, when a 2.5 per cent grade was walked, with an outlay of 59 kg. m. It seems probable, therefore, that the low increment in the heat-output per kilogrammeter found with A. J. 0., W. K., and E. D. B. is due to the method of apportioning the heat for standing and horizontal walking requirements, rather than to the fact that the values were actually low. The average increment due to grade-lift for E. D. B. was 7.0 gram-calories, and for the group of five subjects, 7.2 gram-calories. Omitting A. J. 0. from the average, since he had but one experiment, the average value for the four remaining subjects is 7.6 gram-calories per kilogrammeter of work done. In the discussion of the results of the horizontal- walking experiments, it was seen that some evidence of a training effect appeared in the later experiments with E. D. B. (See tables 34 and 43, pp. 141 and 159.) The data obtained in the experiments on grade walking do not offer so great an opportunity for a study of the effect of training upon the oxygen consumption and the heat-production with a definite amount of work as might be expected, owing to the difference in the conditions of the experiments and to the more or less progressive increase in work as the research continued. This increase in work was due to the fact that hi the earlier experiments the lower grades were used when the subject was less practiced in walking, and as the series progressed the grades were gradually increased, so that in the later experiments the higher grades were used when the subject may be said to have been trained in walking. Near the close of E. D. B.'s five months of service as a subject, low grades were again used in a few experiments, and STEP-LIFT IN GRADE WALKING. 243 these are the only results which are at all comparable with data obtained in the earlier part of the series, when the subject was un- trained. These low-grade experiments were, however, so few in num- ber and, particularly, the total amount of work was so small, being in all cases under 300 kg. m. per minute, that the data do not lend them- selves to the critical discussion of the effect of training upon the energy cost per kilogrammeter of work done in walking up-grade. STEP-LIFT DURING GRADE WALKING. The measurement of the step-lift during horizontal walking is com- paratively simple as determined by the revolution of the work-adder wheel, supplemented and controlled at tunes by the kymograph tracings of the spring pointer of Dr. C. Tigerstedt. 1 (See p. 30.) The results of these measurements have been discussed in an earlier section. (See p. 155.) An attempt was made to measure the step-lift in grade walking by the method used in the horizontal-walking experiments. There is, however, a decidedly different type of step-lift in grade walking as compared to that in walking on a level, for in grade walking the weight is of necessity thrown more on the toes than in walking on a horizontal plane and the center of gravity must be farther forward. In the grade- walking experiments the body continually moved up an inclined plane (the treadmill belt), which, to be sure, was continually passing by the body of the subject. Was any of the movement recorded as step-lift actually due to the "grade-lift" of the body, or was the record an un- contaminated measure of the particular type of step-lift necessarily accompanying grade walking? It was considered that the position of the subject on the treadmill was o closely determined by the mouth- piece and the fork of the step-lift recorder which rested on his shoulder (see fig. 1, p. 19) that he could alter his relative position on the tread- mill but little. This supposition has been confirmed by the photo- graphic tests previously described on page 31. It is recognized, how- ever, that possibilities of error in these measurements are present, as was the case with the measurements for walking on a level. As pointed out in the description of the technique (p. 33), the manner of measuring the step-lift in these experiments is fairly open to criti- cism as to the position of the fork. (See fig. 1, p. 19.) After the preparation of this manuscript was nearly completed, it seemed desirable to make tests to note the influence, if any, of a change in position of the fork with relation to the plane upon which the subject walks. 2 Consequently, the mill was set at a 30 per cent grade and the fork was placed in a position parallel to the belt of the mill. Under 'C. Tigerstedt, Skand. Arch. f. Physiol., 1913, 30, p. 299. 2 The author wishes to acknowledge his indebtedness to Dr. F. G. Benedict, who carried out these experiments at a time when he himself was unable to co-operate. 244 METABOLISM DURING WALKING. these conditions the cord attached to the fork and leading to the kymo- graph passed upwards hi a direction perpendicular to the plane of the mill to a pulley above, thence to a second pulley, and thence to the kymograph. Unfortunately, none of the original subjects in this research could be secured for the later tests, as they were no longer in the vicinity of Boston. Consequently, another subject was used, and tests were made with the fork not only hi the new position, but also for comparison in the position used in the research. No measurements of the metabolism accompanied these tests. Two speeds of walking were employed, one approximately 50 to 55 meters per minute and another from 75 to 87 meters per minute. The results show that when the fork was parallel to the treadmill belt there was, as a matter of fact, a somewhat greater step-lift than when the fork was left in the original position. (See % 1.) The string was then attached at the belt of the subject in the position originally used by Benedict and Murschhauser 1 and the results com- pared with those obtained with the fork parallel to the treadmill belt. Very satisfactory agreement was obtained in all cases. The important point brought out in this test is that the step-lift as measured by the method employed in the entire research reported in this publication, namely, with the fork parallel to the floor and not to the angle of ascent, is in all probability somewhat too small rather than too large. In the absence of the original subjects, particularly E. D. B., it seemed unde- sirable to make an attempt to establish closely related correction fac- tors by comparing the step-lift during grade walking as measured with the probable step-lift measured with the fork in what we now believe to be the proper position, i. e., parallel to the surface of the treadmill. The method of studying the locomotion of ihan, devised by Braune and Fischer, 2 is extraordinarily ingenious. No one who reads their original memoir and the subsequent analyses by Fischer can fail to be impressed by this profitable method of attack. It is particularly un- fortunate for us that, if experiments were made by these authors on grade walking, no photographic results were given and no data pub- lished. Had this been the case, we feel sure that the element of un- certainty as to the step-lift in grade walking would have been quickly dispelled. Apparently from purely theoretical considerations, Amar 3 has sketched the hypothetical movements of the body in grade walking and clearly indicates a somewhat higher oscillatory motion perpen- dicular to the plane of the belt than would obtain in horizontal walking. 'Benedict and Murschhauser, Carnegie Inst. Wash. Pub. No. 231, 1915, pp. 32 and 40. J Braune and Fischer, Abhandl. d. math.-phys. Klasse d. Konigl. Sschsischen Gesellsch. d. Wissensch., Leipsic, 1895, 21, p. 153. 3 Amar, Le moteur humain, Paris, 1914, p. 476. STEP-LIFT IN GRADE WALKING. 245 Step-lift per minute. In considering the step-lift per minute, recorded in column g of tables 52 to 55, it is seen that although the variations present in horizontal walking between experimental periods with like conditions are likewise to be found here, the amount of lift per minute increased in approximate conformity with the speed for the same grade. It may also be noted that the lift per minute for the same or approxi- mately the same speed increased with the grade, and that the total lift reached a very appreciable amount at the higher grades and speeds. Thus, E. D. B. had a total step-lift per minute of 7.1 meters when walking on a 30 per cent grade at 69.5 meters per minute and on a 40 per cent grade at 65 meters per minute, as compared with a total step- lift per minute of 1.7 meters on a 5 per cent grade at 65.4 meters per minute. (See table 55, p. 209.) Step-lift per step. The lift per step likewise shows an increase with the higher grades and speeds. W. K., on March 4, walking on a 3.6 per cent grade at 69 meters and 114 steps per minute, had a lift per step of TABLE 66. Average step-lift per step of E. D. B. in grade walking for approximately the same speeds but with varying grades. (Values per minute.) Step-lift per step at speed of Per cent grade. Less than 60 to 70 70 to 80 60 meters. meters. meters. cm. cm. cm. 1.18 2.05 2.53 5 1.36 1.85 2.63 10 2.50 3.68 4.06 15 3.13 3.95 4.78 20 4.04 4.98 4.69 25 4.61 5.68 6.36 30 5.38 5.94 35 5.43 6.57 40 6 18 6.88 45 5.84 1.2 cm., while on June 17, on a 25 per cent grade at 67 meters and 120 steps per minute, it was 4.6 cm. (See tables 15 and 54, pp. 71 and 199.) A summary of the data obtained for the lift per step of E. D. B. during grade walking is given in table 66, grouped according to grade and speed. The values for horizontal walking (0 per cent grade) are also given for comparison. The lift per step for E. D. B. with a 5 per cent grade and a speed below 60 meters per minute was 1.36 cm., only slightly greater than the average found during horizontal walking (1.18 cm.) for approximately the same speed. For the highest grades and speeds, however, the lift per step was between 6 and 7 cm. 246 METABOLISM DURING WALKING. COMPARISON OF STEP-LIFT IN HORIZONTAL AND GRADE WALKING. Although the data for the step-lift as measured may be found scat- tered throughout the tables, it seems desirable to make a direct com- parison of the step-lift in horizontal walking with the step-lift in grade walking as measured by the apparatus pictured in figure 1. Such comparison should, however, be subject to the criticism and at least theoretical corrections brought out in the discussion of the technique on page 31. Using the data for our most frequently employed sub- ject, E. D. B., we have collected in table 67 a series of values comparing the step-lift of this subject during horizontal and grade walking at an TABLE 67. Comparison of step-lift of E. D. B. in horizontal and grade walking at an approximate speed of 1+5 meters. (Values per minute.) Date and conditions. Grade. Distance walked. No. of steps. Length of step. Step- lift. Step-lift per step. 1915. Horizontal walking: Oct 30 p. ct. meters. 43.9 80.3 cm. 54.7 meters. 0.66 cm. 0.82 Nov 1 44.3 79.7 55.6 .72 .90 2 43.2 79.9 54.1 .70 .88 3 44.5 85.3 52.2 .76 .89 5 46.2 81.9 56.4 .81 .99 6 45.9 80.8 56.8 .75 .93 10 47.8 84.7 56.4 1.00 1.18 17 45.7 79.0 57.8 .78 .99 22 47.4 80.7 58.7 .79 .98 Dec 4 ... 46.7 79.0 59.1 .93 1 18 6 . . 45.0 78.5 57.3 .68 .87 7 45.8 77.1 59.4 .67 .87 Grade walking: Nov 4 5.0 48.2 79.9 60.3 0.99 1.24 6 5.0 48.2 79.5 60.6 1.00 1 26 17 10.3 48.0 81.1 59.2 1.86 2.29 Dec. 7 15.0 46.4 81.3 57.1 2.42 2.98 1916. Feb. 2 25.0 46.5 85.9 54.1 4.31 5 02 8 30.0 46.0 88.8 51.8 4.60 5.18 18 40.0 49.5 89.9 55.1 5.64 6 27 average speed of 45 meters. The different grades used in the grade- walking experiments are also indicated. The first half of the table consists simply of a repetition of horizontal walking on different days, and consequently shows no great variation. As a matter of fact, the total step-lift ranged from 0.66 to 1.00 meter per minute on the days selected for comparison, and the step-lift per step from 0.82 to 1.18 cm. Since all of the horizontal-walking data are not here included, it seems unnecessary to assume an average, and it will not be used in the sub- sequent discussion. The values for the grade walking are given in the lower part of the table. It will be noted that the distance walked per minute was slightly higher in most instances than in the horizontal walking. Not- STEP-LIFT IN GRADE WALKING. 247 withstanding the somewhat greater speed in grade walking, the num- ber of steps was not, as a rule, larger than in horizontal walking until a grade of 25 per cent was reached; thereafter the number of steps taken per minute was larger. The step-lift increased very perceptibly with the grade and likewise the step-lift per step. In table 68 a similar comparison is made when the average speed for both horizontal and grade walking was 77 meters per minute. In the upper part of the table the data for horizontal walking are more or less representative of duplicate experiments on different days and show no great variation. During the grade walking there was, as with the slower speed, a very perceptible increase in the number of steps with the higher grades, beginning at 20 per cent, although it is again to be noted that in three of the four tests in grade walking the actual rate of walking per minute was somewhat higher than during the horizontal walking. The step-lift increased pronouncedly, as did the step-lift per step. TABLE 68. Comparison of step-lift of E. D. B. in horizontal and grade walking at an approximate speed of 77 meters. (Values per minute.) Date and conditions. Grade. Distance walked. No. of steps. Length of step. Step- lift. Step-lift per step. 1915 Horizontal walking: Oct. 27 p. ct. meters. 77.7 104.5 cm. 74.4 meters. 2.91 cm. 2.78 28 77.8 106.5 73.1 2.78 2.61 29 78.0 104.8 74.4 2.95 2.81 Nov. 13 76.7 103.9 73.8 2.75 2.65 15 77.0 104.0 74.0 2.83 2.72 16 76.9 103.7 74.2 2.90 2.80 19 77.9 104.1 74.8 2.43 2.33 Dec. 1 76.2 105.3 72.4 2.72 2.58 Grade walking: Nov. 30 10 78.5 101.7 77.2 4.05 3.98 Dec. 16 15 81.3 107.1 75.9 5.17 4.83 31 20 80.1 110.2 72.7 4.69 4.26 1916. Feb. 7 25 75.9 109.3 69.4 6.95 6.36 It was a special consideration of these latter factors, namely, the step- lift and the step-lift per step, that led us to surmise that the method of measurement of the step-lift indicated in figure 1, i. e., with the fork parallel to the floor and not parallel to the plane of walking, might incorporate in the graphic record a certain component that should properly be ascribed to the grade-lift. This surmise led to the series of experiments reported on page 243, from which the conclusion is drawn from tests made on a single subject (unfortunately not one of the original group) that the step-lift as measured was probably not con- taminated by grade-lift, but, if anything, with the fork parallel to the floor, the apparatus does not record so large oscillations of the shoulders 248 METABOLISM DURING WALKING. in a direction perpendicular to the inclined plane of the belt as it does when the fork is parallel to the belt. It is assumed, therefore, in sub- sequent discussion, that the step-lift as actually measured and re- corded in this publication is not far from correct, though probably somewhat below rather than above the true value. WORK OF ASCENT. In addition to the work which the subject performed of lifting the body-weight to the elevation produced by the grade of the treadmill, ordinarily considered as the only positive work done in grade walking, we must also take into account the work which was done (theoretically, at least) in lifting the body a few centimeters at each step in the rise and fall of the body due to the step-lift. That the work of grade-lift is positive and, in the transportation of a superimposed load up a road, may be of economic significance, must not obliterate the fact that physiologically, if the body, or indeed a superimposed load, is lifted a few centimeters during each step, positive work is being accomplished, uneconomical though it may be. The sum of the work due to the step- lift and that due to the grade-lift represents what may therefore be designated as the "work of ascent." From the step-lift as actually measured and the weight of the body, the work performed as a result of the step-lift has been computed and is recorded in column h of tables 52 to 55. The "work of ascent" is given in column i of the same tables. In considering the work done during grade walking, we may see from previous discussion that, owing to the uncertainty as to the actual amount of work due to the step-lift, the exact apportionment of the total work between that due to the elevation of the body in the grade- lift and that due to the step-lift is difficult. Doubtless a more subtle analysis of the mechanics of locomotion in the line of the particularly ingenious method of Braune and Fischer, 1 possibly, by means of specially illuminated and figured backgrounds, and the ultra-rapid motion-picture camera, may clarify the situation. Since this may not be made at the present time, and it is desirable to present a hitherto neglected factor in the computation of the efficiency of the body in grade walking, we have assumed that, as a result of the experiments carried out as this report was being written and the considerations set forth on pages 243 to 244, the measurements of the step-lift obtained in this research during grade walking included none of the elevation due to the grade-lift component, and they thus represent the true step-lift. The computations of the work due to this factor which have been made from them may thus be considered as giving the true results. 1 Braune and Fischer, Abhandl. d. math.-phys. Klasse d. Konigl. Sachsischen Gesellsch. d. Wissensch., Leipsic, 1895, 21, p. 153. EFFICIENCY IN GRADE WALKING. 249 EFFICIENCY IN GRADE WALKING. EFFICIENCY IN WORK DUE TO GRADE-LIFT. ^ efficiency with which the work of grade walking was done has been computed from the increment in the heat-output and the kilo- grammeters of work performed due to grade-lift, the value of 426.6 kg. m. being used as the mechanical equivalent of 1 calorie. 1 In calculating the percentages, 2.34 gram-calories is taken as the heat equivalent of 1 kg. m. Since the heat values here used are increments above the standing and horizontal- walking requirements, the results represent "net" efficiencies. 2 A study of these efficiencies in relation to the work performed in grade-lift is of physiological importance. (See column q of tables 52 to 55, and column o of table 56.) For A. J. O. and W. K., with a 3.6 per cent grade, and E. D. B. with a 5 per cent grade, the efficiencies are all high (approximately 40 per cent). The amounts of work done on these low grades were 172 kg. m. for A. J. 0., and under 150 kg. m. for W. K. and, in most cases, for E. D. B. This amount of work is equivalent to approximately one-third of a calorie as compared with the total heat measured of 3 to 4 calories, from which total must be de- ducted the standing and horizontal- walking values. An error of 0.1 calorie in estimating these values would be a very appreciable amount of the one-third calorie attributable to the work. With these grades the horizontal- walking factor was determined on each day for W. K. and E. D. B. (except for one day in April) and the standing value was the average, with E. D. B., of 23 determinations, with a maximum dif- ference of 0.13 calorie and a maximum deviation from the average of 0.07 calorie. The difference between the average standing value of 1.10 calories taken for W. K. and the two standing values nearest the date on which he walked with a 3.6 per cent grade differ by only 0.01 and 0.05 calorie. These variations are small, and while they might account for the irregularities in the efficiencies for the different days, they would not account for the constant high efficiencies for these low grades. We are inclined to the opinion that the subject walking on a low grade and performing less than 200 kg. m. of work did so at an efficiency in the neighborhood of 40 per cent. With 250 kg. m. of work and upward, the efficiency for all the subjects is seen to approach 30 per cent. The effect of the speed on the efficiency with which the work was done may be found from table 56, in which the figures indicate a de- creasing efficiency with increasing speed for a definite grade, which 1 Armsby, Principles of animal nutrition, New York, 2d ed., 1906, p. 233. A so-called "best" value of 426.7 is reported in the Smithsonian Physical Tables, Washington, 1920, table 212, p. 197. Our computations were made previous to the publication of this edition by means of the slightly lower figure of 426.6. 2 We have not considered "gross" efficiency in this discussion. Obviously all the data for its computation are readily found in the several tables. 250 METABOLISM DURING WALKING. naturally results in an increased amount of work. To compare more directly the effect on the efficiency of the work performed, the average efficiency for both W. K. and E. D. B. with increasing amounts of work is given hi table 69. These average values are a composite for different grades and speeds and show in each case that, as the work increases, the efficiency diminishes. TABLE 69. Relation between efficiency in grade-lift and amount of work performed in grade walking by W. K. and E. D. 5. Kg. m. of grade lift. Efficiency. W. K. E.D.B. 400 to 500 500 to 600 600 to 700 800 to 1,000 1,000 to 1,600 p. ct, 28.6 26.2 26.2 25.8 p. ct. 32.7 32.5 31.7 30.0 29.3 When the periods for each day are compared, we find that the effi- ciency tends to fall as the forenoon progressed, this drop being apparent for all subjects, grades, and speeds. It is believed that this is due to fatigue, for though the subject may not be conscious of it for some hours, the onset of fatigue must be early in the performance of work. It must be admitted, however, that no connection appears between the amount of the decrease hi efficiency and the amount of work done. Thus, with E. D. B. hi the two periods on February 22, when he did over 1,500 kg. m. of work, there was a decrease in the second period of but 0.5 per cent, while on several days when he performed less than one- third this amount of work the efficiency fell during the forenoon 1 to 2 per cent. It is perfectly possible that the subject's physical condition played a part here which obscures the comparison. The average efficiencies of these five subjects as given in table 70 is 33.4 per cent; if we exclude A. J. O., with whom there was but one experiment with a low grade, we find the average to be 31.3 per cent. The lowest average efficiency was with W. K. at 29.4 per cent, and the highest with E. D. B. at 33.7 per cent. The results for H. R. R. are,- we confess, surprising. From our observation, which was influenced,* no doubt, by the fact that this subject practically collapsed after the sixth period on May 1, while performing but 550 kg. m. of work, we expected much lower efficiencies from him than from the others, and yet his average value of 31.1 per cent is in accord with that of T. H. H. and of W. K. It should also be mentioned that in the last period of May 1, just before he succumbed, the efficiency for H. R. R. was not different from that in the three preceding periods. The efficiencies of EFFICIENCY IN GRADE WALKING. 251 these men (omitting A. J. O.) lie so close together that no statement may be made regarding superiority. The fact that E. D. B. stands somewhat above the others may be accounted for by the relatively large number of experiments in which there was a small amount of work. As has been stated, hi all such experiments the subjects show a higher efficiency than in those with a greater amount of work. There is hardly sufficient ground in the small difference for E. D. B. to suppose that as an individual he was any more efficient than the other four men. TABLE 70. Efficiency of subjects in grade-walking experiments. Subject. No. of experi- ments. Efficiency in grade-lift. Minimum. Maximum. Average. A. J. O 1 6 8 48 79 p. ci. p. ct. p. ct. 41.8 31.1 30.8 29.4 33.7 H. R. R 29.3 28.9 25.2 27.0 32.5 34.4 44.2 48.7 T. H. H W. K E. D. B Average 33.4 31.3 Average omitting A. J. O Many reports on the mechanical efficiency of men doing various forms of work have been published. One of the earliest was that of Edward Smith, 1 who used a tread- wheel and from whose results Helmholtz 2 computed a gross efficiency of 20 per cent. A large amount of work on the energy exchange in man during walk- ing has been done by both Zuntz and Durig and their associates, to which reference has already been made. (See pp. 8 to 13.) In the summary of the results 3 given in table 71 and obtained with men walk- ing on a treadmill at grades of 12.68 to 36.2 per cent, the net efficiencies range from 25.7 to 46.5 per cent, with a distinct tendency to approach 33 per cent. This is hi close accord with our results. The efficiencies of men performing other kinds of work, such as using a wheel and brake, lifting weights, and riding a stationary bicycle, have been studied by a number of investigators, and their results have been discussed by Benedict and Cathcart. 4 In many cases there is no clear distinction between the "gross" and "net" efficiency, and in several studies only the carbon-dioxide output is determined. Natur- ally, these results show considerable variation, depending upon the subject, the form of work, and not infrequently upon the method of iSmith, Edward, Phil. Trans., 1859, 149, p. 681. 2 Helmholtz, Proc. Roy. Inst., 1861, 3, p. 347. 3 Drawn from Durig, Denkschr. d. math, natur. Klasse d. kaiserl. Akad. d. Wissensch., 1909, 86, p. 299. 4 Benedict and Cathcart, Carnegie Inst. Wash. Pub. No. 187, 1913, p. 101. 252 METABOLISM DURING WALKING. computation employed. It may be said that these net efficiencies are, as a rule, lower than for walking and are nearer 27 to 28 per cent than they are to 33 per cent. The first studies made with the bicycle ergometer were carried out by Atwater and Benedict 1 and showed net efficiencies of 19.6 per cent as an average of 14 experiments. Later experiments reported by Benedict and Carpenter 2 showed efficiencies of 20 to 23 per cent, and other experiments by Benedict and Cathcart 3 with a professional bicyclist, M. A. M., gave efficiencies approaching 33 per cent. TABLE 71. Efficiency of men in treadmill walking with different grades, as summarized by Durig. 1 (Values per minute.) Grade in per cent. Grade-lift. Heat-output per kg. m. of grade-lift. Efficiency. Experimenters. kg. m. gm.-cal. p. ct. 31.0 602.9 8.68 26.9 459.6 8.90 26.3 594.4 9.11 25.7 691.6 8.89 26.3 31.0 (620.0) 774.3 (6.98) 8.58 33.5 27.3 Schumburg and Zuntz. 784.3 8.14 28.7 810.5 8.50 25.7 757.7 8.21 28.5 763.1 8.11 22.9 30.4 555.0 677.0 6.82 6.84 34.3 34.3 A. and J. Loewy and L. 36.2 812.0 6.53 35.8 Zuntz. 23.0 6.430 36.4 s 6.664 35.1 > Frentzel and Reach. J 12.68 680.2 5.488 42.7 12.68 489.6 5.402 43.3 12.68 26.2 12.68 359.8 795.1 369.6 6.064 7.991 7.223 38.6 29.3 32.1 Zuntz, Loewy, Muller, and Caspari. 12.68 580.5 7.057 33.2 18.24 570.8 5.033 46.5 21.6 14.7 830.3 695.3 6.73 6.87 34.9 34.1 JDurig. 2 1 Durig, Denkschr. d. math.-natur. Klasse d. kaiserl. Akad. d. Wissensch., 1909, 86, p. 299. *Ibid., p. 341. An apparent typographical error in the average for the heat-output per kilo- grammeter of grade-lift for 21.6 per cent grade has been corrected here. It may be stated, therefore, that the human machine can accomplish various forms of muscular work at a net efficiency greater than 25 per cent, and that grade walking is the most efficient of the various forms of exercise thus far studied, the efficiency for this probably being 33 or more per cent. J Atwater and Benedict, U. S. Dept. Agr.. Office Exp. Sta. Bull. No. 136, 1903, p. 190. *Benedict and Carpenter, U. S. Dept. Agr,, Office Exp. Sta. Bull. 208, 1909. 'Benedict and Cathcart, Carnegie Inst. Wash. Pub. No. 187, 1913, p. 121. EFFICIENCY IN GRADE WALKING. 253 EFFICIENCY IN WORK OF ASCENT. The total heat-output during grade walking is made up of a number of factors: first, the basal requirement for standing; second, the super- imposed work of forward progression, including the step-lift ; and third, the actual elevation of the body as a result of the grade. A computa- tion of the proportion of energy ascribable to the actual lifting of the body, such as is done not only in the grade-lift but in the superimposed step-lift, necessitates the deduction of certain basal values. Of these, obviously that for the standing metabolism would be one, but the deduction of the standing metabolism only does not allow for the energy of forward progression. Ordinarily, the entire energy due to horizontal walking is deducted before the efficiency for grade walk- ing is computed, but this is illogical, since the energy required for forward progression includes a not inconsiderable proportion rightly attributable to the elevation of the body in the step-lift, which is an integral factor in grade walking. When the increments in the total heat of horizontal walking over the requirement for the standing position are compared with the computed heat ascribable to the work done by the body in the step-lift, it is seen that the heat-output due to this secondary elevation of the body was an appreciable percentage of the total increase in energy and varied with the speed at which the man walked. (See table 43, p. 159.) Consequently, in computing the efficiency for the work of ascent, a deduction should be made from the total heat-production of a certain proportion of the energy required for horizontal walking at a similar rate, this deduction depending upon the speed of walking. It has seemed unwise to use all of our data in computing the effi- ciency for the work of ascent, inasmuch as the method of computation is at best based upon problematical assumptions. We have, however, computed the efficiency for a number of typical days with E. D. B. at varying grades and speeds. These results are recorded in table 72. This table is best considered in relation to table 55 (p. 209), the data hi columns a to e being drawn from that table. The work of the total lift of the body, that is, the work of ascent, which includes both the grade-lift and the step-lift in grade walking, is recorded in column c. The total increment hi the heat over standing in column d represents the total heat measured during the grade walking, less the standing requirement. The total heat due to the horizontal component is recorded in column e and, as originally recorded in table 55, was obtained by first multiplying the weight of the body by the horizontal .component of the distance walked and then multiplying the result by the factor for the energy required for each horizontal kilogrammeter (column n of table 55). The first important new step is the computation of the heat due to the horizontal component, less that fraction due to the step-lift in walking 254 METABOLISM DURING WALKING. on a level. From table 43, the percentage of the increase in heat due to the step-lift in horizontal walking may be computed for E. D. B. for the average speeds. These percentages, although made up of somewhat widely varying individual values, are as follows : For 45 me- ters, 9 per cent; for 55 meters, 11 per cent; for 65 meters, 15 per cent; for 72 meters, 16 per cent; and for 77 meters, 18 per cent. The pro- portions of the total heat for the horizontal component to be deducted from the total heat over standing are, therefore, for a speed of 45 meters, TABLE 72. Efficiency for work of ascent of E. D. B. 1 (Average values per minute.') (a) <&) (c) (d) Heat due to horizontal Heat due to (JO Total component. work of ascent. Work of incre- Efficiency Date. Grade. Dis- tance walked. total lift (work of ascent). ment in heat over stand- ing. (e) Total. (/) Propor- tion due to step- lift (0) Less amount due to step-lift. W Total. (d-g) (0 Per kg.m- of work of ascent. for work of ascent. 2.34X100 t 11IL. eX(100-/) (h+c) 100 1915-16. p. ct. meters. kg. m. cals. cals. p. ct. cals. cals. gm.-cals. p. ct. Nov. 4 5.0 48.2 198.1 2.08 1.25 1.14 0.94 4.7 49.8 6 5.0 48.2 200.7 1.98 1.23 1.12 .86 4.3 54.4 17 10.3 48.0 398.9 3.20 1.27 1.16 2.04 5.1 45.9 Dec. 7 15.0 46.4 555.5 4.09 1.20 9 1.09 3.00 5.4 43.3 Feb. 2 25.0 46.5 976.4 7.00 1.27 1.16 5.84 6.0 39.0 8 30.0 46.0 1,104.8 7.34 1.22 1.11 6.23 5.6 41.8 18 40.0 49.5 1,526.6 10.44 1.26 1.15 9.29 6.1 38.4 Nov. 9 5.0 54.8 243.3 2.24 1.35 1.20 1.04 4.3 54.4 10 5.0 55.4 244.7 2.19 1.40 1.25 .94 3.8 61.6 23 10.0 57.2 484.1 3.76 1.39 1.24 2.52 5.2 45.0 Dec. 8 15.0 58.3 702.2 5.28 1.47 1.31 3.97 5.7 41.1 17 20.0 53.4 809.2 5.55 1.29 11 1.15 4.40 5.4 43.3 Feb. 3 25.0 52.6 1,036.6 7.63 1.42 1.26 6.37 6.1 38.4 9 30.0 53.6 1,291.4 8.80 1.42 1.26 7.63 5.9 39.7 16 35.0 57.6 1,568.3 11.10 1.49 1.33 9.77 6.2 37.7 21 40.0 57.1 1,774.1 12.50 1.46 1.30 11.20 6.3 37.1 Nov. 11 5.0 66.0 299.6 2.72 1.76 1.50 1.22 4.1 55.8 26 10.0 66.5 586.8 4.52 1.69 1.44 3.08 5.2 45.0 Dec. 13 15.0 66.8 798.0 5.84 1.61 1.37 4.47 5.6 41.8 20 20.0 66.4 1,052.9 7.14 1.64 15 - 1.39 5.75 5.3 44.2 Jan. 5 25.0 69.3 1,326.5 9.90 1.78 1.51 8.39 6.3 37.1 Feb. 11 30.0 69.5 1,676.6 11.81 1.84 1.56 10.25 6.1 38.4 22 40.0 65.2 1,996.5 14.45 1.66 1.41 13.04 6.5 36.0 Nov. 13 5.0 74.1 375.3 3.16 1.97 1.65 1.51 4.0 58.5 Dec. 3 10.0 70.5 650.8 4.87 1.85 1.55 3.32 5.1 45.9 14 15.0 73.4 909.5 6.54 1.92 1.61 4.93 5.4 43.3 21 20.0 70.3 1,078.8 7.76 1.72 16 1.44 6.32 5.9 39.7 Feb. 5 25.0 71.0 1,429.1 10.24 1.91 1.60 8.64 6.0 39.0 12 30.0 71.5 1,710.6 11.86 1.91 1.60 10.26 6.0 39.0 Nov. 30 10.0 78.5 704.1 5.62 2.15 } { 1.76 3.86 5.5 42.5 Dec. 16 15.0 81.3 975.5 7.29 2.09 1.71 5.58 5.7 41.1 31 20.0 80.1 1,205.4 9.94 2.22 ! 18 1.82 8.12 6.7 34.9 Feb. 7 25.0 75.9 1,565.6 11.42 2.15 1.76 9.66 6.2 37.7 table 55 (p. 209) for data in columns a to e. EFFICIENCY IN GRADE WALKING. . 255 100 per cent less 9 per cent, or 91 per cent; for 55 meters, 89 per cent; for 65 meters, 85 per cent; for 72 meters, 84 per cent; and for 77 meters, 82 per cent. The values to be deducted for the heat due to the hori- zontal component, as thus computed, are given in column g. The heat due to the work of ascent may then be calculated by deducting from the total increment in heat over standing (column d) the heat due to the horizontal component corrected for that due to the step-lift (column g}. The resulting values are recorded in column h, and represent the increase in heat actually ascribable to the work of ascent. Dividing these values by the kilogrammeters of work of ascent (column c), we obtain the increment in heat per kilogrammeter of work of ascent. This is best expressed in gram-calories as recorded in column i. From these latter values the efficiency of the body for the total work of ascent is readily computed by using 2.34 gram-calories as the heat equivalent of 1 kg. m. These percentages are given in column j, and represent net efficiencies. From the general consideration of the efficiency of the body as com- puted on the basis of grade-lift, it was found that these values repre- sented an average for all of the subjects not far from 33 per cent. (See table 70, p. 251.) By this new method of computation, which ascribes a larger amount of work to the body, since the step-lift is superimposed upon the grade-lift, we find that for this subject (E. D. B.) the per- centage of efficiency is larger, in some instances actually reaching 50 to 60 per cent, with a maximum on November 10 of 61.6 per cent. Under the separate groupings for the different speeds, the experiments have been arranged in the order of increasing grade, running for the most part from 5 to 40 per cent, except with the two higher-speed groups when the steepest grades were but 30 and 25 per cent, respectively. An inspection of the figures for these efficiencies in column j shows that, in general, the percentages fall as the grade increases, i. e., within each speed group there is a distinct tendency for the efficiency to be some- what lower with the higher grades. It is more than likely that the difficulty in computing the ratio be- tween the fraction of the energy expended for the grade-lift and that expended for the standing and horizontal walking when an extremely low grade was employed may in part account for the high values here found, a point which has been touched upon in the earlier dis- cussion of the grade-lift measurements. With constant grade, but varying speeds, the percentage efficiency for the 10 per cent grade remains practically constant throughout the entire series at 45 per cent; with the 15 per cent grade they likewise are reasonably constant; with a 30 per cent grade a slight decrease in the efficiency is apparent, which may also be seen with the 40 per cent grade. The whole problem of computing the efficiency on this basis may reasonably be challenged on the grounds that not only is the value of the step-lift uncertain, but also we are not dealing here with "effective" 256 METABOLISM DURING WALKING. external muscular work. The transportation of the body up-grade or the transportation of a superimposed load, such as was done in many of Durig's experiments, may definitely be classed as "effective" mus- cular work. The step-lift, both with the body and with the superim- posed load, can not be considered in the ordinary process of walking as effective external work. Nevertheless we believe that this treat- ment has distinct physiological interest in the strong suggestion that attention to the type of gait, particularly in minimizing the step-lift, may not be without definite economic importance in considering the human body as an efficient machine. EFFECT OF LAMENESS UPON THE EFFICIENCY OF E. D. B. As has been stated elsewhere, E. D. B. developed a lameness in the instep of his right foot early in January. As a result, the experiments with him were discontinued for a period of three weeks, beginning with January 10. On inquiry it developed that he had been conscious of some pain in the instep for a number of days, although he had made no complaint. The question accordingly arose whether the lameness was of sufficient moment to vitiate the results of the standing and grade- walking experiments on January 3, 4, and 5. The metabolism data obtained on these days have accordingly been collected in table 73. For comparison, the data are included for the standing experiment of December 31 and the grade- walking experiment of January 1 before the lameness developed, and for the grade-walking experiment of February 4, when the lameness had been cured by three weeks of rest. As would be expected, the metabolism during standing was evi- dently not affected, as the data for January 3, 4, and 5 agree well with those obtained on December 31, before the lameness developed. In the grade-walking experiments of January 3 and 4, the values for the energy cost per kilogrammeter and the percentage efficiencies show slight changes from corresponding data obtained on January 1 and February 4; nevertheless the differences are so slight that they may be considered as within the limits of experimental error. The efficiency for the other day (January 5) agrees well with those of January 1 and February 4. There is therefore no reason to discredit the values re- ported for these three days. On January 10, when the subject began walking preliminary to the experimental period, the pain in his instep was so severe that it was necessary to end the experiment. The standing data for this day have not been included hi any of the tables previously discussed, but are given in table 73. These values show a very slight increase in the carbon-dioxide production and heat-output. Although it was noted in the protocols of the experiment that the subject "stood mostly on the left foot" and "favored his right leg," the difference in the metabolism values is too small to indicate that the subject was standing at a dis- PHYSIOLOGICAL EFFECTS OF GRADE WALKING. 257 advantage. Zuntz and Schumburg 1 report that when one of their subjects walked with a lame foot, the metabolism increased 9.2 per cent. This might well have occurred with E. D. B. on January 10 had we insisted on continuing the experiment, as his lameness caused him great discomfort in walking. On January 3, 4, and 5, the lameness was apparently of too little account to affect his efficiency. TABLE 73. Effect of slight lameness upon the metabolism and efficiency of E. D. B. (Value* per minute.) Date and conditions. Carbon dioxide. Oxygen. Respiratory quotient. Heat-output. Standing: No lameness: c. c. c. c. cals. Dec. 31 211 257 82 1 24 Slightly lame: Jan. 3 210 250 .84 1 21 4 212 244 .87 1.19 5 206 253 .81 1 22 Too lame to walk grade: Jan. 10 224 251 .89 1.23 Heat- Date and conditions. Work due to grade- lift. Carbon dioxide. Oxygen. Respira- tory quotient. output per kg. m. of grade- Efficiency. lift. Grade walking: No lameness: kg. m. c. c. c. c. gm.-cals. p. ct. Jan. 1 935 2,010 2,272 0.88 8.3 28.2 Feb. 4 932 1,903 2,084 .91 8.0 29.2 Slightly lame: Jan. 3 628 1,183 1,451 .82 7.5 31.2 4 872 1,723 1,965 .88 7.8 30.0 5 993 2,054 2,252 .91 8.2 28.5 PHYSIOLOGICAL EFFECTS OF GRADE WALKING. RESPIRATION-RATE DURING GRADE WALKING. The respiration-rates during the experiments with grade walking (see tables 13 to 16, pp. 69 to 78) tended to increase slightly in each period as the forenoon progressed. This increase, hi a few instances, was as large as 5 respirations per minute, but in the majority of cases it was only 1 or 2 respirations per minute over that of the first walking period. The increase between periods does not appear to be associated with the amount of work which the subject was performing, and the differences were no greater when the larger amounts of work were done. The average respiration-rates are also given in table 56 (p. 221), in which the experimental data have been grouped according to the grade J Zuntz and Schumburg, Physiologic des Marsches, Berlin, 1901, p. 265. 258 METABOLISM DURING WALKING. and speed of walking, and not according to the sequence of the experi- ments. As a rule, the changes in the rates progressed gradually and uniformly with the increase in the speed and the amount of work per- formed. The maximum rate was found with the maximum work with each subject, although this is not true of the minimum amount of work. The difference in the respiration-rates for the different subjects is noticeable. At the medium speed of 60 to 65 meters per minute with a 10 per cent grade, T. H. H. had a low rate of 17.9 as compared with W. K.'s rate of 26.1; E. D. B. had a rate of 26.7 when walking on a 25 per cent grade at 70 to 75 meters per minute as compared with W. K.'s rate of 40 under similar conditions. 170 160 150 140 R 130 40 120 35 110 30 25 / V Liter 55 45 35 25 15 " / X jy X ^ /, X /j ,. / X X " x. * 9 -^ ^ X 2O * . X 7 ^ x.PL USE 5PIRATI ITILAf DN ON - 1 r<^ *V a. RE +-VE IOO 300 500 700 900 Kg.ms. FIG. 28. Pulse-rate, respiration-rate, and pulmonary ventilation of W. K. during grade walking, referred to kilogram- meters of work. (Values per minute from table 56.) The curves for the average respiration-rates for W. K. and E. D. B. in table 56 have been plotted and presented in figures 28 and 29. The curve for E. D. B. shows a uniform rate of increase, but that for W. K. indicates a greater rate of increase beyond 300 kg. m. From these curves an estimate has been made of the respiration-rates per minute for increasing amounts of work. (See second column of tables 74 and 75.) From these values have been calculated the total and percent- age increases hi the respiration-rate over the standing requirement, and also the increments per 100 kg. m. as the unit of work done. The PHYSIOLOGICAL EFFECTS OF GRADE WALKING. 259 rapid increase in the respiration-rate of W. K. as the work increased manifests itself here in an increase over the standing requirement per 100 kg. m. of work, while for E. D. B. the increase per 100 kg. m. diminished as the amount of work became larger and reached con- stancy at about 800 to 900 kg. m. The percentage increase over the standing value for W. K. ranged from 16 to nearly 100 per cent, with an increase per 100 kg. m. of 7 to 11 per cent. With E. D. B. the increase was as high as 40 per cent for the first 100 kg. m., but it fell rapidly and above 700 kg. m. the increase per 100 kg. m. was con- stant at a level of 7 and 8 per cent. 160O FIG. 29. Pulse-rate, respiration-rate, and pulmonary ventilation of E. D. B. during grade walking, referred to kilogrammeters of work. (Values per minute from table 56.) TABLE 74. Respiration-rale of W. K. with increasing amounts of work in grade-walking experiments without food. (Values per minute.) 1 Increase over stand- Percentage increase Respiration- ing rate (21.1) over standing rate. Kg. m. rate during of work. grade walking. Total. Per 100 kg. m. Total. Per 100 kg. m. 200 24.5 3.4 1.7 16 8 300 25.3 4.2 1.4 20 7 400 26.8 5.7 1.4 27 7 500 28.6 7.5 1.5 36 7 600 31.3 10.2 1.7 48 8 700 34.3 13.2 1.9 63 9 800 38.0 16.9 2.1 80 10 900 41.7 20.6 2.2 98 11 ^aaed upon figure 28. 260 METABOLISM DURING WALKING. TABLE 75. Respiration-rate of E. D. B. with increasing amounts of work in grade-walking experiments without food. (Values per minute.} 1 Kg. m. of work. Respiration- rate during grade walking. Increase over stand- ing rate (15.4) Percentage increase over standing rate. Total. Per 100 kg. m. Total. Per 100 kg. m. 100 21.5 6.1 6.1 40 40 200 22.0 6.6 3.3 43 22 300 23.0 7.6 2.5 49 17 400 23.6 8.2 2.1 53 13 500 24.1 8.7 1.7 56 11 600 24.5 9.1 1.5 59 10 700 25.0 9.6 1.4 62 9 800 25.7 10.3 1.3 67 8 900 26.5 11.1 1.2 72 8 1,000 27.5 12.1 1.2 79 8 1,100 28.0 12.6 1.1 82 7 1,200 29.1 13.7 1.1 89 7 1,300 30.5 15.1 1.2 98 8 1,400 31.6 16.2 1.2 105 8 1,500 32.8 17.4 1.2 113 8 J Based upon figure 29. PULMONARY VENTILATION DURING GRADE WALKING. The data for the puhnonary ventilation during the grade-walking experiments are also given in detail in tables 13 to 16, pages 69 to 78, from which it is seen that though on some days the ventilation increased from period to period, this increase was not so pronounced and appears to be much more nearly uniform and less influenced by continued exer- cise than was the case with the respiration-rate. Naturally the volume varied with the individual subjects and primarily with the amount of work that was performed. The variations in the rate of increase due to increases in grade and speed are best seen in the group averages hi table 56, from which it is evident that, almost without exception, the average ventilation increased with each increase in speed for the several grades or each increase in grade for a uniform speed. The figures thus give some indication of what may be required by a person when doing a definite amount of muscular work. The significance of these figures in the designing of suitable gas-masks is obvious. In general, it may be said that 17 to 21 liters per minute represents the average rate for a moderate speed of 50 to 60 meters per minute (approximately 2 miles an hour) when the subject is walking on a 10 per cent grade, or when he is doing approximately 335 kg. m. of work. The amount of ventila- tion increased as the grade and speed increased to a maximum of 85 liters per minute, as in the case of E. D. B. with 1,569 kg. m. of work. As previously stated (see p. 192), the use of the mouthpiece in these grade- walking experiments did not apparently affect the normality of the results obtained for the respiration-rate and the pulmonary venti- lation, notwithstanding the quickened respiration and greater ventila- tion as a consequence of the severe exercise. PHYSIOLOGICAL EFFECTS OF GRADE WALKING. 261 The ventilation-rates for W. K. and E. D. B. have been plotted and are included with the respiration curves hi figures 28 and 29, based on kilo- grammeters of work performed. In these two curves the total venti- lations of W. K. and E. D. B. are practically the same for like amounts of work up to 500 kg. m. ; beyond this point the total ventilation of W. K. exceeds that of E. D. B. for similar amounts of work. From the curves hi figures 28 and 29, an estimate has been made of the venti- lation requirements for increasing amounts of work. (See tables 76 and 77.) From these values are found the total and percentage in- TABLE 76. Pulmonary ventilation of W. K. with increasing amounts of work in grade-walking experiments without food. (Values per minute.) 1 Increase over stand- Percentage increase Kg. m. of work. Pulmonary ventilation (reduced). ing rate (6.5 liters). over standing rate. Total. Per 100 kg. m. Total. Per 100 kg. m. liters. liters. liters. 200 16 9.5 4.8 146 73 300 19 12.5 4.2 192 64 400 22 15.5 3.9 238 60 500 26 19.5 3.9 300 60 600 31 24.5 4.1 377 63 700 39 32.5 4.6 500 71 800 47 40.5 5.1 623 78 900 57 50.5 5.6 777 86 'Based upon figure 28. TABLE 77. Pulmonary ventilation of E. D. B. with increasing amounts of work in grade-walking experiments without food. ( Values per minute.) l Increase over stand- Percentage increase Kg. m. of work. Pulmonary ventilation (reduced). ing rate (9.1 liters). over standing rate. Total. Per 100 kg. m. Total. Per 100 kg. m. liters. liters. liters. 200 16 6.9 3.5 76 38 300 19 9.9 3.3 109 36 400 22 12.9 3.2 142 36 500 26 16.9 3.4 186 37 600 29 19.9 3.3 219 37 700 32 22.9 3.3 252 36 800 37 27.9 3.5 307 38 900 41 31.9 3.5 351 39 1,000 46 36.9 3.7 405 41 1,100 51 41.9 3.8 460 42 1,200 57 47.9 4.0 526 44 1,300 64 54.9 4.2 603 46 1,400 71 61.9 4.4 680 49 1,500 79 69.9 4.7 768 51 1,600 87 77.9 4.9 857 54 on figure 29. 262 METABOLISM DURING WALKING. creases over the standing requirements as well as the increase over the standing requirements per 100 kg. m. of work performed. These figures show an increment over the standing requirement of 777 per cent for W. K. for 900 kg. m. and 857 per cent for E. D. B. for 1,600 kg. m. of work. For a unit amount of work of 100 kg. m., however, there is a gradual decrease up to 600 kg. m. for W. K. and to 800 kg. m. for E. D. B. Beyond these points the ventilation per 100 kg. m. increased hi each case, reaching 5.6 liters for W. K. as compared with 3.5 liters for E. D. B. at 900 kg. m. PULSE-RATE DUHINQ GRADE WALKING. The pulse-rates for a definite grade and speed of walking are influenced hi these experiments by several factors, but chiefly by (1) the daily rate for the standing position, which, as seen from tables 3 to 7, shows variation from day to day; and (2) the variation in the speed at which the subject walked, due to our inability to control exactly the speed of the treadmill. Furthermore, it is noticeable hi the data in tables 13 to 16 that almost without exception the average pulse-rate increased with each succeeding period. As has been stated, the pulse-rates for the individual periods represent an average, in most cases, of 3 one-minute records. This increase from period to period may, in some cases, be due to the gradual alteration in the speed at which the subject walked; but since there are numerous instances when the pulse-rate increased though the speed decreased, the increment hi pulse-rate is more likely due to fatigue with the continuation of the work. The increase from period to period is seen to have a variation of from 2 to 3 beats per minute to as high as 15 beats, with a total accumulated increase in the pulse-rate during a forenoon in a few instances.of as much as 30 beats a minute while the same work is being performed. This rise in the pulse-rate, due to the cumulative effect of the exercise, makes the values given as the average for the day misleading, for an average made up of 5 or 6 continuous walking periods would be much higher than when but half that number of walking periods are included in the experiment. Furthermore, any failure to secure the record of the pulse-rate for a period tends to change the average value reported for the day. In spite of these difficulties and of the recognized objection to these so-called daily averages, it is believed that the errors that are present are minimized to a considerable extent by the number of the experi- ments and that the general picture is correct. An inspection of the daily averages in tables 13 to 16 shows an approximate pulse-rate for an approximate amount of work performed. This is more apparent in table 56, in which the values are not averages for the individual days, but for the periods falling within 5-meter speed groups with different grades. PHYSIOLOGICAL EFFECTS OF GRADE WALKING. 263 The high pulse-rate of H. R. R. in most of the standing and hori- zontal-walking experiments persists, also, in the grade experiments, in which a rate of 140 was found with the subject walking on a 10 per cent grade at a speed of 60 to 65 meters per minute (about 2.5 miles an hour), as compared with a rate of 125 and 103 for W. K. and E. D. B., re- spectively, under similar conditions. (See table 56.) T. H. H. shows the exceptional behavior of a falling pulse with in- crease in the speed for the single grade used in his experiments. This is due, hi part, to the considerable number of periods on April 6 and 7, when all of the period data for the lowest speed (55 to 60 meters per minute) were obtained. Out of the 9 periods composing the average for a speed of 55 to 60 meters a minute, the 3 highest were the last records of a continuous forenoon performance on April 7 of 6 periods. The average pulse-rate for this speed was therefore high on account of the cumulative effect of the work on these days. However, this will not entirely account for the fact that this subject had a decreasing pulse- rate with increasing work. On April 15, when he performed his largest amount of work, his pulse-rate was distinctly lower than on the pre- vious days. A week intervened between this experiment and the pre- ceding one, but we have no record that his physical condition was different in this experiment from that in any other. Evidently the experiments with T. H. H. were not continued long enough to deter- mine his representative pulse-rate in the performance of a moderate amount of exercise. W. K. and E. D. B. offer more data for comparison. These values indicate that, with occasional exceptions, the pulse-rate progressed with the speed for each grade. The increase in the pulse-rate in rela- tion to the amount of work performed is depicted in the curves for these subjects in figures 28 and 29, 1 which are based upon the averages in table 56. They indicate a practically uniform increase with increase in the amount of work done. The curve for W. K. ascendfs more sharply than that for E. D. B., the average pulse-rate increasing from 115 to 176 beats for an increase from 298 to 891 kg. m., or approximately one beat for every 9.7 kg. m. increase in work, while the average pulse- rate of E. D. B. increased from 84 to 186 beats for an increase in work from 59 to 1,569 kg. m., or an increase of one beat for every 14.8 kg. m. increase in work. If these values are referred to the average basal value found in the standing experiments (79 for W. K. and 78 for E. D. B.), the increase for the maximum amount of work is found to ba 123 per cent for 891 kg. m. with W. K. and 138 per cent for 1,569 kg. m. with E. D. B. This would correspond to an increase of approximately 7 kg. m. for every 1 per cent of increase in the pulse-rate for W. K. and llkg. m. for E. D. B. 'All of the curves in these two figures represent averages of estimates drawn independently by three members of the Laboratory staff. METABOLISM DURING WALKING. Comparing these increases in the pulse-rate with the increases in the oxygen consumption for like amounts of work, we find that with W. K., when he was doing the maximum amount of 891 kg. m. of work, the increase in the oxygen consumption over his standing requirement was 818 per cent, and with E. D. B. for 1,569 kg. m., the increase was 1,205 per cent. (See table 57, p. 224.) This shows the enormous increase in the oxygen consumption as compared with the increase in the pulse- rate. How this great increase in oxygen consumption is provided for is still undetermined. Certainly, neither the increase in the pulse- rate nor any probable increase in the oxygen-carrying capacity of the blood due to the more complete combination with the hemoglobin can account for it, and an increase in the volume output of the heart, with perhaps a large pulmonary oxidation 1 under these conditions, seems probable. TABLE 78. Pulse-rate of W. K. with increasing amounts of work in grade- walking experiments without food. (Values per minute.) 1 Increase Percentage increase over standing rate. Kg. m. of work. Pulse- rate. over standing rate (79). Total. Per 100 kg. m. p. ct. p. ct. 300 112 33 42 14 400 122 43 54 14 500 133 54 68 14 600 144 65 82 14 700 155 76 96 14 800 166 87 110 14 900 177 98 124 14 upon figure 28, p. 258. From the curves in figures 28 and 29, estimates may be made of the increase in pulse-rate with increasing amounts of t work, as was done for the total oxygen consumption, total heat-output, and other factors. These estimates are recorded in tables 78 and 79, together with the increase over the average values for the standing experiments. The percentage increases in the last column of these tables show that with W. K. the pulse-rate increased 14 per cent for each 100 kg. m. of work done over his average pulse-rate of 79 during standing; with E. D. B. the increase over his standing average of 78 was more nearly 10 per cent for each 100 kg. m. The increase in the oxygen consumption on this same basis varied from 139 to 97 per cent for W. K. and from 150 to 77 per cent for E. D. B. (See tables 58 and 59, p. 229.) The approximation to constancy in the percentage increase of the pulse- rate with each 100 kg. m. of work is in marked contrast to the fall in Henderson, Am. Journ. Physiol., 1912-13, 31, p. 352. PHYSIOLOGICAL EFFECTS OF GRADE WALKING. 265 TABLE 79. Pulse-rate of E. D. B. with increasing amounts of work in grade- walking experiments without food. (Values per minute.} 1 Increase Percentage increase over standing rate. Kg. m. of work. Pulse- rate. over standing rate (78). Total. Per 100 kg. m. j>. ct. p. ct. 100 85 7 9 9 200 95 17 22 11 300 103 25 32 11 400 111 33 42 11 500 119 41 53 11 600 126 48 62 10 700 133 55 70 10 800 140 62 80 10 900 147 69 88 10 1,000 153 75 96 10 1,100 159 81 104 9 1,200 165 87 112 9 1,300 171 93 119 9 1,400 177 99 127 9 1,500 184 106 136 9 1,600 189 111 142 9 'Based upon figure 29. the percentage increase over the standing requirement for the oxygen consumption with each 100 kg. m. of work, clearly indicated in tables 58 and 59. In figures 30 to 32, a few typical curves are given of the pulse-rates of E. D. B. during grade walking with the accompanying changes before and after the exercise. The pulse-rates immediately preceding and following the beginning and end of the exercise will be considered in another section in discussing the transitional periods for changes in FIG. 30. Typical pulse curves of E. D. B., with subject standing, walking on a level, and walking on an incline. (Values per minute.) 2, subject standing; 3*, walking on a level; 3**, walking on an incline. Black points, records during experimental periods; open circles, records between periods. Curve A, Nov. 5; B, Nov. 6, 1915. 266 METABOLISM DURING WALKING. 180 160 140 120 100 80 60 c A h 3 jJi / ' .-i 3 / / n I Vr 7 \ I I V J,' 72 meler \ 5 / 3 )20 * a. m. 3 10 a J 4O 1 1 ft) O JJ conditions (pp. 297 to 305). As in similar figures, the number 1 in- dicates that the subject was sitting, and 2 that he was standing. The time at which the subject began walking is indicated by the figure 3. 1 The points indicated by open circles represent per minute values ob- tained in the interval between the experimental periods. Curve A in figure 30 gives a picture of the rate when the subject was walking on a level up to 10 h 33 m a. m., stood until 10 h 40 a. m., and thereafter walked on a 5 per cent grade until 12 h 27 m p. m., when he again stood for a short tune. The course of the curve is but little altered by the change to grade walking, and there were no sudden or marked variations in the rate during the forenoon. Curve B in figure 30 is also for an experiment with a _ 5 per cent grade preceded by 12 walking on a level, but on this day the speed was a little higher. Curve B has the same general appearance as curve A, however, except that the rise due to the walking is somewhat more marked. Both curves in- dicate a slight fall at the begin- ing of the walking on a level and the usual fall in the pulse-rate when the "grade walking ceased at the end of the experiment. In curve A the pulse-rate after the walking ceased reached more nearly the initial level than in curve B, but as the observations were continued only 7 minutes after the walk- ing ceased, no information could be gained as to how long a period elapsed before the pulse returned to normal. In the curves hi figures 31 and 32, showing the rate after severe exercise, the pulse was still above the normal after 5 'It should be noted that the arrow indicates the time of the change and not the pulse-rate. For instance, in fig. 31, curve A makes direct connection between the two readings at 9 h 31 m and 8 b 43 m a. m. ; the walking began at 9 h 42 m a. m. If the arrow were taken to indicate the pulse- rate at this time, the rate would appear to be 142. On the contrary, it was probably more nearly 66 to 68, and the curve for the rise due to the activity of walking is actually much steeper than here drawn. 160 B i I A ,2 140 f E t* \ "( 120 L V \ \ \ 100 i v * jmters \! V 80 J 60 a*"- i am a J 4 J K )00 ' 2 4 > 11 00 4 4 Fio. 31. Typical pulse curves of E. D. B., with subject standing and walking on an incline. (Values per minute.) 2, subject standing; 3, walking on an incline. Black points, records during experimental periods; open circles, records between periods. Curve A, Feb. 12; B, Feb. 14, 1916. PHYSIOLOGICAL CHANGES IN TRANSITION. 267 60 to 7 minutes, but here again the records were not continued a sufficient length of tune to determine whether the pulse-rate returned to the normal value or remained at a higher rate for some hours, as was observed by Benedict and Cathcart. 1 Curve A hi figure 31 shows a rise from an average rate of 64 to a rate of 146 when the subject began to walk on a 30 per cent grade. When he stopped walking at the end of the first period, there was an immediate drop of 53 beats. When the walking began again, the pulse-rate rose to 170, with a greater fall at the end of the second period of walking and a still greater rise for the third period of walking. Curve B in figure 31 shows essentially the same characteristics as those of curve A in the same figure. ei.i io ro 180 160 140 120 100 80 ( C it , ,, / 5 T^ 1 62i Mtor* S ,^_ >iPi * j 10 w a D * \> 1iro ' 12 >OO 180 * i ', 160 / V 14O / s i?n * i \ \ 100 > 80 / 3 > n 2-V ?no W*. a f i )OU 1 1 1RO F .* in 2 '* 1 J 140 r' 1 i?n 1 > d 5 100 Rn ' fin r-' 3i?m. 3 J 3 1 t I 00 o Fio. 32. Typical pulse curves of E. D. B., with subject standing, and walking on an incline. (Values per minute.) 1 , aubj ect sitting ; 2, standing ; 3, walking on an incline. Black points, records during experimental periods; open circles, records between periods. Curve A, Feb. 16; B, Feb. 18; C, Feb. 17; D, Feb. 19; E, Feb. 22; F, Feb. 21, 1916. In figure 32 curves A and B represent pulse records obtained when the walking was continuous and illustrate the gradual rise in the pulse- rate due to the cumulative effect of the exercise. As no records of the pulse-rate were made in the intervals between the walking periods in the other experiments in figure 32, there is accordingly no picture of the fall which took place while the subject was standing in these intervals. (See C, D, E, and F.) The curves in other respects are similar to those previously discussed, and show increases in the pulse- 'Benedict and Cathcart, Carnegie Inst. Wash. Pub. No. 187, 1913, p. 154. 268 METABOLISM DURING WALKING. rates of 60 to 80 beats or more in the first period of walking. Curve E represents the records for the day on which E. D. B. performed the maximum amount of work (February 22), which was accompanied by the maximum pulse-rate and the maximum oxygen consumption. In this experiment, also, no records were made during the intervals be- tween the periods. As will be seen, the severe exercise in the walking : periods increased the pulse-rate per minute over 100 beats. BODT-TEMPERATTJRE DURING GRADE WALKING. The measurements of the body-temperature of E. D. B. during grade walking were begun on January 5, 1916, and are given in table 16a, page 88. These temperature records were made with a resistance ther- mometer placed in the rectum (see p. 36), and represent average values. It must be understood that identical conditions did not prevail for all experiments. These differences in the conditions, such as in the length of preliminary walking, the position of the subject between the periods, i. e., sitting, standing, or walking, and the difficulties which sometimes developed due to the displacement of the thermometer as the subject walked or changed from standing or sitting to walking or the reverse, all tend to make direct comparisons difficult. Each record must there- fore be considered for the most part by itself. This can best be done by a series of curves. In table 16a the data indicate a temperature rise between most of the periods. When this did not occur, the cause may generally be found in the fact that the subject rested in these intervals and there was accordingly no cumulative effect of work. This rise in tempera- ture can not be due to the diurnal variation which is known to exist, for the periods are too brief and as a rule the differences between succeeding periods were from 0.1 to 0.3 C. Differences of over 1 C. are occasionally found, which may be due to the cumulative effect of work. On March 4 there was a fall of 1 C. between the sec- ond and third periods. The subject was sitting in the interval between these periods and the temperature fell continuously during that time. It continued to fall for several minutes after the walking in the third period began and remained at the lower level during the walking in the fourth period. Evidently the technique was at fault on this date, although no mention is made in the protocols of any difficulty. Temperature records taken on 14 different days are given in figures 33 to 37. The tunes of change from sitting to standing or standing to walking or the reverse are indicated by arrows and the usual numeral designations, i. e., 1, sitting; 2, standing; 3, walking on an incline. As in the pulse curves, the black points represent records taken during the experimental periods, and the open circles the records between the periods. Although all of the body-temperature material for these 14 days have been plotted in the curves, it does not seem necessary to PHYSIOLOGICAL EFFECTS OF GRADE WALKING. 269 reproduce the records for the other days. The data graphically given were selected with a view to showing the body-temperature with a variety of grades and speeds of walking, and the response of the tem- perature record to the changes from rest to work and the reverse. During the experiments on these days the room temperature was, on the average, about 21 C., varying not more than 2 or 3 C. from this in any experiment. 37.20 37.00 36.80 36.60 A \ L^VJ A*-*r ' * f /* A 24p f > . Mr / s> rv fV ^^ * C. 37.40 37.20 37.OO 36.80 fY B / a 1 p^** -i_-***i y ? 5px 40rrw L tor* gh T ^- \ \ v^ 37.40 37.20 37.00 36.80 36.60 c r fV 1 / C / r~F> 1 i 47m, tort jC M^S ^ ^ 1 I V Sm. 2 t> O JO OT W ** 11 W ** *" 12Sfm. Z Jo ) FIQ. 33. Typical body-temperature curves of E. D. B., with subject standing and walking on an incline. (Values per minute.) 1, subject sitting; 2, standing; 3, walking on an incline. Black points, records during experimental periods; open circles, records between periods. Curve A, Apr. 15; B, Apr. 14; C, Apr. 6, 1916. In figure 33 are three curves (April 15, 14, and 6) for periods with the subject in the standing position, also walking with grades of 2.4, 5, and 10 per cent. The temperatures for the standing position were fairly constant until the point when walking began, which is indicated by the arrow and the numeral 3. 1 The rise in the temperature curve J The curves are drawn by connecting the points for the consecutive readings. The locations of the numbers and arrows for change in position refer to the approximate time and not to the temperature. 270 METABOLISM DURING WALKING. with the change to walking on these three days is not large in compari- son with that shown in subsequent figures, the records in figure 33 being chosen for low grades and speeds. This increase does not become apparent for approximately 10 to 15 minutes after the walking began, and the rate of increase is relatively gradual. In the first two curves, A and B, there is usually no noticeable fall in temperature when, as in both experiments, the subject sat down at the close of the walking periods. In the curve for the 10 per cent grade (curve C), a more rapid rise in temperature is evident, with a tendency to a decrease between the periods. This is apparent, also, after the second walking period with the 5 per cent grade in curve B, when the temperature during walking had reached 37.46 C. The curve for the 10 per cent grade (curve C) shows a sudden fall in temperature following the change to walking before the heat due to the exercise becomes noticeable. This was possibly owing to change in resistance of the leads when the sub- ject removed the blanket (see p. 37), or possibly to some change in the position of the thermometer itself. In figure 34 are three different types of curves (February 2 and 25 and March 8). Here the grades were 25 and 30 per cent, with speeds from 46 to 60 meters per minute. The curves all show an immediate rise in temperature as soon as walking began, the response being within 2 or 3 minutes. This is in contrast to the curves in figure 33. The rise in temperature in curve B was 1.23 C. during 28 minutes of walk- ing, with a maximum of 38.30 C. With the same grade, but a speed of 51 meters, the increase in three periods of walking was 1.45, 1.49, and 1.52 C., respectively. (See carve C.) As soon as the walking stopped and the subject sat down, the temperature fell as rapidly as it rose and in approximately 40 minutes had reached the original level. The effect of difference in position may be seen by the fact that the fall at the end of the periods was greater and more rapid in curve C, when the subject sat down with the cessation of walking, than in curve B, when the subject stood in the intervals between the walking periods. In the last period in curve B the walking was stopped, although the measurement of the metabolism was continued somewhat longer. While the rise in temperature ceased and the records almost imme- diately showed a level when the walking stopped, the fall in temperature in this case did not occur until the close of the period. Curve A in this figure shows a record for an experiment in which but three observa- tions were taken during each period. In this experiment the subject sat down after each period and the temperature did not rise so high nor fall so abruptly as hi curve C, hi which the grade and speed were greater and the walking was continued through two periods and the corre- sponding interval before the subject sat down. In figure 35 are four curves (February 29, 22, 17, and 18) of the tem- perature changes when E. D. B. was walking with a speed of 68 to 50 PHYSIOLOGICAL EFFECTS OF GRADE WALKING. 271 meters per minute (2.5 to 2 miles an hour) on a 30 to 40 per cent grade, and performing approximately 1,200 to 1,600 kg. m. of work. With a grade of 30 per cent and a speed of 68 meters per minute, the body- temperature increased regularly during the 32 minutes of continuous walking, reaching a maximum of 38.23 C., with a total rise of 1.63 C. (See curve A.) The fall in temperature when the subject stopped 37.80 37.60 37.40 37.20 37.00 36.80 36.60 36.40 9 f / J| / A / \l / ^\ / 2 ) s / 25p 4 46rr ton / / V Fm. 10 Z j ,,oo a ) W 12 * 36.70 FIG. 34. Typical body-temperature curves of E. D. B., with subject standing, and walking on an incline. (Values per minute.) 1, subject sitting; 2, standing; 3, walking on an incline. Black points, records during experi- mental periods; open circles, records between periods. Curve A, Feb. 2; B, Feb. 25; C, Mar. 8, 1916. walking and stood, at 10 h 55 m a. m., was not so rapid as that shown by the curve D when a higher body-temperature was reached, or when the subject sat after walking, as shown by curve C in figure 34. A more rapid fall began at ll h 40 a. m., when the subject sat down, which again was retarded during the standing period of 20 minutes about 12 o'clock. At 1 p. m., after 2 hours and 5 minutes of inter- mittent standing and sitting, the temperature had not reached the initial level. METABOLISM DURING WALKING. c. 38.40 38.20 38.00 37.80 37.60 37.40 37.20 37.00 36.80 36.60 36.40 92V 10 38.50 38.30 38.10 37.90 37.70 37.50 37.30 37.10 36.90 36.70 9 ^ B A M [ / / 40 p. r 65m* t / 3 V*r 00^ 20 J 10 X c. 39.10 38.90 38.70 38.50 38.30 38.10 37.90 37.70 37.50 37.30 37.10 36,90 C A / " \ * / V \ r^ 7 / "a 35 62 .cl neltrl 7 "+Z\r- J "*-3 3 c. 38.90 38.70 38.50 38.30 38.10 37.90 37.70 37.50 37.30 37.10 36.90 > 1 D / \ 7 1 f / / ft 3.Cl mctws / - ,^ -^ W 9 * * 10- aa - * 11 FIG. 35. Typical body-temperature curves of E. D. B., with subject standing, and walking on 'an incline. (Values per minute.) 1, subject sitting; 2, standing; 3, walking on an incline. Black points, records during experi- mental periods; open circles, records between periods. Curve A, Feb. 29; B, Feb. 22- C, Feb. 17; D, Feb. 18, 1916. Curve C gives the body-temperature for the experiment of February 17, when there was an initial period of standing followed by several periods when the subject walked on a 35 per cent grade at a speed of 62 meters per minute. The subject stood after each walking period. In the first 19 minutes of walking the temperature rose 0.82 C., i. e., at the rate of 0.04 C. per minute. The total effect of the exercise was an increase in the body-temperature of approximately 1.7 C., with a maximum body-temperature of 38.80 C. PHYSIOLOGICAL EFFECTS OF GRADE WALKING. 273 In curve D a graphic record is given of the body-temperature found in the experiment of February 18, with E. D. B. walking at an average rate of 50 meters per minute on a 40 per cent grade. Here, also, the walking was preceded by a period of standing, with practically the same body-temperature at the beginning as in curve C. In contrast to February 17, the rise in the first 19 minutes of walking was but 0.66 C., or 0.03 C. per minute. The slope of the curve for the grade walking is practically constant up to 38.50 C., and thereafter the rate of in- crease diminishes. Although the grade was 5 per cent greater on February 18 than it was on February 17, a decrease in speed of 12 me- ters per minute resulted in a smaller amount of work on this day (1,188 kg. m. as compared with 1,306 kg. m. on February 17), which was sufficient to retard the rise in the body-temperature. In this experiment there was continuous walking from 9 h 25 m to 10 h 35 m a. m. (1 hour and 10 minutes), with a total increase in temperature of 1.96 C. and a maximum temperature of 39. 10 C. The subject was much out of breath when he stopped walking and was sweating freely. As stated earlier, the electric fan was not used for cooling during the experi- ments with E. D. B. (See p. 37.) Curve B in figure 35, which gives records for the experiment on Feb- ruary 22, when the grade was 40 per cent and the speed 65 meters per minute, represents the temperature on the day when E. D. B. did his maximum amount of work of 1,569 kg. m. per minute with an oxygen consumption of 3,132 c. c. per minute, and a total heat-output per minute of 15.65 calories. Although the maximum body-temperature was not so great as that shown in curve D, when the walking was con- tinuous for 1 hour and 10 minutes, yet the increment during walking is shown by curve B to have been 1.62 C. in 23 minutes. This was an increase at the rate of 0.07 C. per minute. The rate of increase is thus larger than that shown in curves C and D when the temperature rose 0.04 and 0.03 C. per minute, respectively, and the work performed was less. It may reasonably be said, therefore, that for amounts of work over 1,000 kg. m. per minute, the body-temperature may increase from 0.03 to 0.07 C. per minute for the first 10 to 20 minutes, with a maximum total increase of 1.5 to 2.0 C. The curves hi figure 36 (February 26 and 15) are included to show more especially the fall in the body-temperature after the walking stopped. In the experiment of February 26 (curve A) the grade was 30 per cent and the speed 70 meters per minute. The walking ceased at 10 b 32 m a. m., and in the subsequent period of 2 hours and 3 minutes, during which the man alternately stood and sat, the body-temperature fell 1.58 C. This fall brought the body-temperature below the level in the first standing period of the forenoon. In the experiment on February 15 the grade was 35 per cent and the speed was 45 meters per minute. When the walking ceased at ll h 7 m 274 METABOLISM DURING WALKING. a. m., the body-temperature decreased rapidly, the fall amounting to 1.14 C. in 12 minutes, or 0.09 C. per minute. Unless the technique was at fault, which has not been revealed by a careful inspection of the records, this change in temperature of the body in cooling is by far the greatest and most rapid we have found. A possible explanation, but one for which our records give no data, is that the subject stood without the usual blanket covering. In this case, with the thin, short-sleeved, and short-legged athletic suit worn by the man, the radiation would be greatly increased. The curve would thus indicate that the un- restricted liberation of heat from the body can be as rapid as the sudden production of heat following the beginning of muscular exercise. 88.60 38.40 sazo 3&00 S7.60 7.00 3740 37.20 37.00 6.80 30.60 sa.7o J\ t\ A B A Jy / t "\ 38 K> / | / V [ / 1 rs i mm / \ 5730 / J. J ^ I % * \ ! 37 10 / 1 '\ 3690 lA A . / 1 36.70 fc IP- * * C Itt. ' OT * Fio. 36. Typical body-temperature curves of E. D. B., with subject standing, and walking on an incline. (Values per minute.) 1, subject sitting; 2, standing; 3, walking on an incline. Black points, records during experimental periods; open circles, records between periods. Figure 37 (a grouping of curves for February 18 and 22, March 23, and April 8) gives four contrasting curves showing typical changes in body-temperature. The curves for the experiments with a 40 per cent grade (February 18 and 22) have already been shown in curves D and B in figure 35. These are in strong contrast to the curves for the experiments of April 8 and March 23, in which the grades were 10 per cent and the speed of walking 36 and 62 meters per minute, respectively. The lowest curve of the four (that for April 8, when the smallest amount of work was done) shows that the rise in temperature was not large and that the fall between the periods was slight. Apparently, at the close of the last period, the rise in temperature was approaching a limit. The curve for the other experiment with a 10 per cent grade (March 23) indicates a more rapid increase in temperature, with a more decided fall between the periods. There is no evidence that the rise had reached its limit when the experiment ceased. The two curves with steeper grade (40 per cent) show similar characteristics, but in greater degree. PHYSIOLOGICAL EFFECTS OF GRADE WALKING. 275 The average body-temperature is of special interest in experiments in which the energy changes are determined by direct calorimetry and in which an accumulation of heat hi the body escapes direct measure- ment. The temperatures as here reported may not be considered as representing the average values for the whole body, for, as has been stated in earlier publications, 1 the temperature of the body as a whole has a wide range. The data given here represent the temperature of the rectum only. If, however, we accept these values as repre- senting the body average, we see that the temperature may be increased from 1 to 2 degrees, which, with a body-weight of 60 kg. and an assumed FIQ. 37. Contrasting curves of body-temperature of E. D. B., with subject standing and walking on an incline. (Values per minute.) 1, subject sitting; 2, standing; 3, walking on an incline. Black points, records during experimental periods; open circles, records be- tween periods. specific heat of 0.83 C., results hi a storage of 100 calories of heat in the body, for which allowance must be made in all studies by direct calorimetry. Since, however, the amount of heat stored in the body is dependent on so many conditions, such as clothing, air-currents, and intensity of work, only direct measurements of the body-temperature hi each instance can be relied upon to give this value. It should be noted that we used no electric fan or other artificial means (see p. 37) for keeping the subject cool during the experiments, and the changes Benedict and Snell, Arch. f. d. ges. Physiol., 1901, 88, p. 492; also, Benedict and Slack, Car- negie Inst. Wash. Pub. No. 155, 1911. METABOLISM DURING WALKING. are those due to natural radiation and convection as affected by the very light-weight clothing which the subject wore at the tune. Although the temperatures obtained in this study do not show equal increases for similar amounts of work on different days, yet a higher temperature and a greater increase over the normal temperatures dur- ing standing were usually observed when the work and the metabolism were greatest. As was found with the pulse-rate, there is evidently a general relation between the amount of work and body-temperature. BLOOD-PRESSURE DURING GRADE WALKING. The few readings of the blood-pressure of E. D. B. were made when but small amounts of work were done. Consequently the effect of work on the blood-pressure was not large. As previously stated, these readings were of the systolic pressure only, and were made with the subject standing after a preliminary walking period and again just after the experimental period closed. The results of these measure- ments, which comprise those for 7 days with grade walking, are given in table 16a, page 88. TABLE 80. Blood-pressure of E. D. B. during grade walking in experiments without food. (Values per minute.) Blood-pressure during Increase in Amount of Standing. Walking. due to walking. in walking. 1916. mm. mm. mm. kg. m. Mar. 23. 114 118 4 380 24. 120 127 7 310 Apr. 6 . 116 126 10 284 7. 119 130 11 281 8. 125 139 14- 223 14. 116 128 12 126 15. 118 128 10 59 Excepting for the first period of April 6, the records show close agree- ment for the periods of the same day, with a slight tendency to increase during the forenoon. The blood-pressure increased over the standing values hi all instances, as may be seen from table 80, in which both these values and the kilogrammeters of work done are given. The range of increase was from 4 to 14 mm., with an average value of 10 mm. The blood-pressure for the walking period of March 23 is proba- bly too low, as there was a lapse of 2 minutes after the walking ceased before the pressure was read. There appears to be no indication in these figures of direct connection between the amount of work performed and the blood-pressure, but up to a certain point it appears that the increase in the blood-pres- sure found during grade walking over the values obtained with the subject standing is inversely proportional to the amount of work PHYSIOLOGICAL CHANGES IN TRANSITION. 277 done. This can hardly be regarded as significant, and the probable explanation lies in the technique, for, though the procedure was uni- form, there was probably a variation of 10 to 15 seconds between the cessation of work and the time of reading the pressure. Cotton, Rap- port, and Lewis 1 have shown that the blood-pressure changes rapidly on cessation of exercise, rising abruptly for the first 20 to 60 seconds and then falling to normal in from 1 to 4 minutes. With such small differ- ences in the blood-pressure as here reported, any error in the time of reading would account for this lack of uniformity between the work and the increase in the blood-pressure. The values found are similar in degree to those obtained for the same subject when he was walking on a level (see table 11 a, p. 67), though the increases over the standing values are here a trifle higher on the whole. It is evident that these measurements do not cover a suffi- ciently wide range of work to warrant an estimate of the effects of grade walking upon the blood-pressure, other than to note an approxi- mate increase of 10 mm. in blood-pressure when the work was 300 kg. m. or less. This increase corresponds roughly to an average increase in the oxygen consumption of 500 c. c. per minute, 2 or 9 c. c. per kilogram of body-weight, which is of the same range as that found in the experi- ments with level walking. Liljestrand and Stenstrom 3 with the sub- ject N. S. during level walking found an oxygen increase of 850 c. c. for a rise of 10 mm. in blood-pressure, while for the much lighter sub- ject G. L. the increase in the oxygen consumption was 650 c. c. for an increase of 8 mm. in blood-pressure. These increases would correspond to an increase in the oxygen consumption of 8 and 10 c. c. per kilogram of body-weight. PHYSIOLOGICAL CHANGES IN TRANSITION FROM STANDING TO GRADE WALKING AND THE REVERSE. It is of importance to find out, if possible, how quickly the body re- sponds to the demands made upon it when varying amounts of muscu- lar work are done and how soon it may be said that the body has adapted itself to the new conditions, for the comparison of the results obtained hi this research presupposes that the metabolism has not suffered any change in degree within the daily experimental period and that a sufficient period of exercise has been allowed before the beginning of each day's observations for the bodily functions to become settled. It is, furthermore, important to determine how long the effects of mus- cular work are present after the subject is again at rest. Observations were accordingly made in the grade- walking experiments of the changes in the rates of respiration, pulmonary ventilation, oxygen consumption, and pulse during the transition from standing to walking and from walking to standing. Cotton, Rapport, and Lewis, Heart, 1917, 6, p. 269. 2 See table 59, p. 229. 'Liljestrand and Stenstrom, Skand. Arch. f. Physiol., 1920, 39, p. 211. 278 METABOLISM DURING WALKING. The data for the transitional changes in the respiration, pulmonary ventilation, and oxygen consumption were secured by employing the records of the kymograph according to the methods already described hi giving the results of the study on the effect of the mouthpiece upon the same factors. (See p. 182.) A reproduction of two typical kymo- graph records obtained in these transition periods is given in figure 38. The lower record (A) represents the change from standing to grade walking, and the upper record (B) the change from grade walking to standing. The exact point when the change occurred is indicated FIG. 38. Typical kymograph records of respiration, pulmonary ventilation, and rate of oxygen consumption in periods of transition from standing to walk- ing and the reverse. A, standing to walking. B, walking to standing. The arrows indicate the exact point when change occurred. Records of time and pulmonary ventila- tion adder above each kymograph tracing. in both cases by an arrow. The hill-and-valley effect due to the re- filling of the spirometer with oxygen, and referred to on page 182, may be noted in these records. RESPIRATORY CHANGES IN TRANSITION FROM STANDING TO GRADE WALKING. The observations of the changes due to transition from standing to grade walking were made with the subject standing for 3 or more minutes; the treadmill was then started, and the tracings on the kymo- graph were noted as the subject walked. The data recorded in tables PHYSIOLOGICAL CHANGES IN TRANSITION. 279 81 and 82 were obtained by measuring these kymograph records. The length of time the subject had been standing previous to these transi- tion observations varied considerably, the range being 10 to 50 minutes. As the condition in the transitional periods varied widely, averaging the values, as was done in the regular series of experiments, would give results without significance. The results of each period have therefore been grouped separately and the measurements of the respiration, ventilation, and oxygen consumption for fractions of a minute have been tabulated on the per minute basis. The data for pulmonary ventilation and oxygen consumption, as given in tables 81 and 82, have not been corrected for the temperature changes, as they are intended for approximate comparison only. CHANGES IN RESPIRATION-KATE. The data for the respiration-rate are given in table 81. The respira- tions during the standing before walking were measured from the kymograph curve for full minutes, no measurements being made of the respiration during the last minute of standing, when the blanket was removed from the subject before he began walking. During the first minute of walking each measurement covered approximately 12 seconds and hi the succeeding minutes 15 seconds. As given in the table, however, the respirations for these fractions of a minute have been computed to a per minute rate. By inspecting the figures in table 81, it will be seen that the respira- tion-rate for standing was fairly uniform during the tune of measure- ment, the changes from period to period being slight and thus in keep- ing with the measurements in the standing experiments previously discussed. (See p. 101.) This gives evidence that the respiration-rate had returned to its normal standing value following the walking of the preceding period. In the majority of the periods the increase in the respiration-rate for the first one-fifth minute of walking was at the rate of from 8 to 10 respirations per minute, or, in round numbers, an in- crease of 50 per cent over the standing rate. During the following frac- tion of the first minute there was, on the whole, a tendency to a further increase at the rate of 1 to 3 respirations per minute, though in a few instances there was a fall. The major portion of the increase occurred within the first 12 seconds. In the following minutes, measured in 15-second intervals, the rates were, as a rule, higher as the time ad- vanced, and though there are periods when constancy was apparently reached by the second minute (see second period of March 9, fourth period of March 15, and second, third, and fourth periods of March 17), there are others (March 16 and February 24) which show gams through- out the record. The change in the rate due to transition from standing to walking, except with severe grades (see March 16 and February 24), may be said to occur, however, in the first minute, and the most of the change is in the first 12 seconds. 280 METABOLISM DURING WALKING. TABLE 81. Respiration-rate and pulmonary ventilation of E. D. B. in periods of transition from standing to grade walking. (Values per minute.) Date, condition, and period of measurement. Period I. Period II. Period III. Period IV. Respi- ration- rate. Pul- monary venti- lation (unre- duced) Respi- ration- rate. Pul- monary venti- lation (unre- duced) Respi- ration- rate. Pul- monary venti- lation (unre- duced) Respi- ration- rate. Pul- monary venti- lation (unre- duced] March 9, 1916. Standing measured in minutes 16.3 16.3 16.6 liters. 10.6 10.9 11.5 16.5 16.8 16.2 liters. 11.3 11.3 11.6 17.0 16.2 17.3 liters. 11.5 10.6 11.6 15.5 15.4 17.3 liters. 10.7 10.8 11.6 Walking, 30 p. ct.; av., 49.6 meters: Measured in 1/5 min.: 1st 20.8 22.5 24.3 25.7 27.9 25.2 25.5 31.6 42.6 47.6 26.2 23.9 25.0 25.0 24.1 24.1 27.8 36.0 42.5 44.4 25.8 23.5 23.5 24.8 29.1 27.3 29.6 32.6 44.1 51.0 25.0 24.0 21.8 24.0 25.7 23.6 28.6 33.4 42.1 46.2 2d 3d 4th 5th Following 1/4 min. : 1st 25.4 25.0 23.9 22.7 44.0 46.0 49.5 49.8 29.9 28.0 24.0 22.5 57.0 55.5 51.9 40.7 27.4 27.4 29.1 25.8 52.5 61.6 58.4 44.8 29.0 30.0 28.0 27.8 57.9 64.5 63.7 54.3 2d 3d 4th 5th 24.8 27.1 26.0 27.0 43.1 44.1 45.1 47.2 25.9 24.4 25.1 25.9 41.9 43.1 48.0 52.9 28.7 30.1 31.3 30.1 47.0 51.2 56.2 59.6 28.6 29.8 32.3 33.4 51.2 57.3 62.9 69.5 6th 7th 8th 9th 29.1 27.0 27.7 28.4 53.3 55.3 61.9 48.3 23.4 23.4 26.0 28.8 53.7 55.7 63.4 55.6 31.0 28.4 27.4 26.4 69.1 59.6 51.1 47.5 28.2 28.5 24.8 29.1 67.2 59.3 52.6 50.4 10th llth 12th 13th 27.7 24.9 28.0 29.8 44.2 47.8 52.6 58.3 26.5 24.3 25.3 26.1 49.6 47.8 54.1 60.2 28.9 32.0 32.0 29.3 52.2 62.1 64.0 68.1 32.3 30.0 30.0 30.0 60.2. 64.9 68.8 61.8 14th 15th 16th 17th 28.3 23.7 23.9 26.8 59.0 55.4 46.4 46.5 28.0 26.9 26.9 26.2 67.0 59.5 48.3 50.6 26.6 28.3 31.0 31.0 51.2 47.4 52.9 56.1 24.8 30.0 28.8 29.8 51.5 55.2 57.1 62.6 18th 19th 20th 21st 29.3 27.4 51.3 52.4 26.2 25.8 50.4 55.7 28.7 29.8 31.7 32.8 65.9 59.5 59.6 67.9 22d 23d 24th March 14, 1916. Standing, measured in minutes 16.2 15.7 16.5 17.2 16.6 26.5 30.2 24.4 23.7 29.3 10.7 11.2 11.7 11.5 11.9 25.2 32.0 36.7 38.7 45.3 16.5 16.8 17.5 17.8 10.9 11.3 12.5 13.7 17.5 16.4 16.5 17.4 10.3 10.5 10.5 11.3 17.2 17.3 17.1 17.6 11.2 11.6 11.1 11.8 Walking, 30 p. ct.; av. 59.9 meters: Measured in 1/5 min. 1st 26.0 28.3 27.9 26.7 28.0 24.5 22.2 28.0 35.1 42.1 26.6 26.6 25.6 27.3 25.8 26.7 26.3 33.8 34.5 42.2 26.0 25.0 27.9 27.1 27.9 28.7 32.6 35.8 40.5 43.7 2d 3d 4th 5th PHYSIOLOGICAL CHANGES IN TRANSITION. 281 TABLE 81. Respiration-rate and pulmonary ventilation of E. D. B. in periods of transition from standing to grade walking. (Values per minute.) Continued. Date, condition, and period of measurement. Period I. Period II. Period III. Period IV. Respi- ration- rate. Pul- monary venti- lation (unre- duced). Respi- ration- rate. Pul- monary venti- lation (unre- duced.) Respi- ration - rate. Pul- monary venti- lation (unre- duced). Respi- ration- rate. Pul- monary venti- lation (unre- duced). March 14, 1916cont'd. Walking, 30 p. ct. ; av. 59.9 meters con. Following 1/4 min.: 1st 29.4 25.4 26.4 22.6 liters. 49.9 53.3 55.4 51.2 27.6 28.5 26.1 28*6 liters. 45.9 48.9 51.9 57.2 25.8 26.7 27.2 27.6 liters. 51.2 52.7 57.0 60.3 30.2 27.3 29.2 29.2 liters. 49.4 53.1 61.2 64.0 2d 3d 4th 5th 28.7 27.5 31.4 27.1 58.7 56.2 64.6 58.2 30.2 32.3 24.8 26.4 57.6 59.0 53.3 57.5 27.0 27.6 24.4 27.6 64.1 64.3 60.4 64.7 27.1 25.7 28.0 27.1 63.3 59.2 61.5 63.2 6th 7th 8th 9th 29.0 25.4 26.3 29.4 59.7 53.3 60.3 60.6 26.9 29.7 29.7 26.7 56.0 61.0 63.2 53.8 31.0 33.8 29.7 29.2 67.9 67.0 64.6 68.3 28.9 29.2 26.6 25.5 64.4 66.5 64.4 64.6 10th llth 12th 13th 29.4 28.1 59.2 58.5 30.5 29.6 27.5 60.0 62.2 62.4 26.5 29.2 28.2 26.5 61.1 68.8 64.9 66.1 29.3 28.7 29.4 29.3 69.1 66.8 65.6 68.5 14th 15th 16th. March 15, 1916. Standing, measured in minutes 16.3 16.8 15.5 15.3 11.0 11.2 10.1 9.7 15.0 16.7 16.7 16.7 10.2 11.0 11.3 11.3 16.3 16.9 16.4 16.4 11.7 11.9 9.9 11.5 16.5 17.6 17.4 16.5 17.1 20.9 19.6 22.8 23.5 29.0 10.7 12.8 11.8 10.5 13.0 Walking, 30 p. ct.; av., 69.6 meters: Measured in 1/5 min.: 1st 34.0 26.3 28.4 24.5 26.6 32.9 33.5 31.4 41.9 46.8 22.3 21.8 24.5 24.7 25.5 24.4 35.2 31.0 33.7 44.9 24.1 31.9 24.1 26.4 27.5 20.9 29.5 39.5 37.4 48.3 2d 30.6 40.1 37.1 50.0 3d 4th 5th Following 1/4 min.: 1st 28.6 26.0 29.9 27.4 53.1 57.8 64.4 61.7 28.8 29.6 30.4 26.2 52.6 59.0 61.9 61.8 25.8 28.6 30.2 27.5 51.3 60.1 66.7 65.9 28.7 25.3 26.7 28.9 53.9 59.7 66.7 72.7 2d 3d 4th 5th 29.6 30.1 31.0 29.3 70.0 75.3 76.2 71.9 25.5 24.8 26.5 29.6 67.1 67.4 66.1 75.1 28.4 28.4 28.4 29.1 71.3 72.2 70.1 76.9 28.3 28.7 28.3 30.4 75.9 74.6 72.0 77.3 6th 7th 8th 9th 28.3 26.0 29.0 29.0 69.4 72.2 75.9 70.3 28.2 26.3 26.2 23.5 76.7 68.1 66.9 64.4 31.2 30.5 29.4 26.7 80.4 80.2 72.9 66.6 25.3 28.0 28.6 28.3 75.9 78.7 73.9 75.8 10th llth 12th 13th 31.0 73.3 28.9 30.6 75.3 75.0 24.0 24.0 62.9 67.7 26.6 30.3 74.8 79.4 14th 282 METABOLISM DURING WALKING. TABLE 81 Respiration-rate and pulmonary ventilation of E. D. B. in periods of transition from standing to grade walking. (Values per minute.) Continued. Date, condition, and period of measurement. Period I. Period II. Period III. Period IV. Respi- ration- rate. Pul- monary venti- lation (unre- duced). Respi- ration- rate. Pul- monary venti- lation (unre- duced). Respi- ration - rate. Pul- monary venti- lation (unre- duced). Respi- ration- rate. Pul- monary venti- lation (unre- duced). March 17, 1916. 14.9 14.7 14.1 13.6 15.3 23.8 liters. 9.7 9.9 10.0 8.8 11.2 16.0 16.0 15.6 16.5 16.1 24.0 24.3 24.3 25.2 25.2 liters. 10.3 10.6 10.5 10.5 10.6 20.7 26.9 29.5 31.4 35.2 16.3 17.4 16.6 17.0 16.7 24.0 24.0 24.0 25.4 24.4 liters. 11.0 11.8 11.1 10.3 13.4 22.0 29.5 29.5 34.5 34.6 17.7 17.7 17.7 16.4 16.9 21.7 26.6 25.4 26.6 27.0 liters. 11.2 11.0 11.2 10.9 10.8 18.9 27.7 26.8 36.8 39.9 Walking, 30 p. ct.; av., 52.9 meters: Measured in 1/5 min. : 1st .... 2d 26.5 21.2 20.2 23.0 29.4 24.7 29.7 36.4 3d 4th 5th Following 1/4 min.: 1st 24.9 26.5 26.5 24.6 43.6 47.0 49.3 48.2 26.8 25.5 25.5 26.4 41.4 40.8 42.2 45.4 25.2 25.2 26.1 24.7 40.2 44.1 44.1 43.0 29.3 27.1 25.5 25.7 44.7 45.0 46.4 47.9 2d 3d 4th 6th 25.8 23.2 25.8 27.1 52.6 51.4 50.7 50.8 25.1 26.6 24.9 25.2 46.2 47.6 52.8 49.3 24.0 25.5 27.1 26.7 47.6 55.5 56.4 53.4 26.3 25.4 27.8 27.8 51.5 53.1 55.6 53.0 6th 7th 8th 9th 25.9 28.0 28.9 24.9 53.3 63.4 56.6 52.9 25.7 27.2 25.5 27.2 47.2 50.7 48.0 51.0 25.7 24.0 28.7 26.4 52.5 51.5 57.3 55.7 26.5 27.1 29.1 26.3 50.6 65.0 67.8 66.0 10th llth 12th 13th 26.4 28.0 26.4 25.6 53.1 59.0 53.9 54.1 27.6 31.0 24.9 25.6 54.8 60.8 50.6 52.1 26.4 26.0 26.2 28.0 55.9 51.8 53.1 55.6 28.2 28.1 26.2 25.4 65.2 56.0 52.7 53.4 14th 15th 16th 17th 24.7 53.1 25.6 27.2 61.9 54.2 28.0 28.0 55.9 58.6 27.8 24.6 56.3 55.9 18th March 16, 1918. Standing, measured in minutes: 15.0 16.1 15.1 16.3 18.0 27.2 24.7 28.7 26.3 26.3 10.2 8.3 7.3 7.6 12.4 26.1 31.7 33.9 43.3 50.3 15.3 16.7 14.0 15.4 16.3 26.7 28.2 20.8 20.0 19.2 10.2 8.1 6.7 7.4 9.8 25.0 27.8 33.9 39.1 40.4 17.0 16.3 13.4 17.8 18.3 21.7 20.9 24.3 24.8 23.4 9.3 7.9 6.3 7.6 11.2 29.1 32.0 30.9 36.8 37.8 16.3 15.9 16.6 18.5 7.8 8.3 7.0 7.7 Walking, 40 p. ct.; av., 66.1 meters: Measured in 1/5 min.: 1st 24.8 24.0 26.7 27.9 23.1 32.2 43.3 45.2 43.5 49.2 2d 3d 4th 5th PHYSIOLOGICAL CHANGES IN TRANSITION. 283 TABLE 81. Respiration-rate and pulmonary ventilation of E. D. B. in periods of transition from standing to grade walking. (Values per minute.) Continued. Date, condition, and period of measurement. Period I. Period II. Period HI. Period IV. Respi- ration- rate. Pul- monary venti- lation (unre- duced) . Respi- ration- rate. Pul- monary venti- lation (unre- duced). Respi- ration- rate. Pul- monary venti- lation (unre- duced). Respi- ration- rate. Pul- monary venti- lation (unre- duced). March 16, 1916cont'd. Walking, 40 p. ct. ; av. 66.1 meters con. Following 1 /4 min. : 1st 26.6 28.0 24.6 27.1 liters. 58.3 67.4 66.5 77.5 21.6 24.4 29.6 29.4 liters. 51.0 61.3 79.1 78.0 25.3 29.3 26.6 27.3 liters. 51.0 70.8 71.3 79.6 23.4 24.7 31.4 29.9 liters. 59.8 69.9 87.5 88.6 2d 3d 4th 5th 27.5 27.5 28.9 30.4 76.8 84.1 86.3 88.4 27.5 31.0 31.0 31.0 80.0 90.1 93.9 94.5 31.2 34.0 32.9 36.0 88.0 98.9 98.8 109.9 34.1 31.4 34.1 34.1 99.7 96.5 98.4 98.4 6th 7th 8th 9th 30.0 31.8 28.6 88.2 97.1 91.1 29.9 31.0 29.9 96.3 97.2 93.7 32.4 31.5 34.7 16.7 25.9 20.8 25.9 25.4 27.7 97.0 96.5 103.4 12.2 24.7 21.2 26.1 29.3 35.1 36.0 37.1 36.5 106.8 110.0 108.4 10th llth February 4, 1916. Standing, av. of 3 minutes Walking, 45 p. ct.; av., 44.8 meters: Measured in 1/5 min.: 1st 2d 3d 4th 6th 6th 29.3 29.3 25.4 28.9 31.2 37.0 44.8 44.7 50.1 56.5 7th 8th 9th 10th llth 27.9 24.1 28.1 30.0 29.0 50.3 51.4 51.9 58.2 61.5 12th 13th 14th 15th 16th 26.3 35.0 39.2 33.7 31.3 49.5 73.2 92.6 89.4 81.9 17th 18th 19th 20th 21st 31.3 33.7 30.0 32.0 34.0 34.0 36.5 85.8 92.9 87.1 90.5 96.6 95.1 101.6 22d 23d ." Following minutes: 1st 2d 3d 4th 284 METABOLISM DURING WALKING. CHANGES IN PULMONARY VENTILATION. The data for the pulmonary ventilation (uncorrected for tempera- ture changes) are also included in table 81, and are measured from the kymograph curves in the same time-lengths as the respiration-rate, i. e., full minutes for the standing position and 12 seconds and 15 sec- onds for the walking. When the subject changed from standing to walking, the measured values indicate that the ventilation doubled within the first 12 seconds and continued to increase throughout the first and into the second minute. By the close of the second minute this increase appeared to diminish in several of the periods, but, as a rule, it continued into the third minute. Beyond the third minute, though increases occasionally appear in the values, they were not per- sistent, and are without uniformity in direction. The values in the fifth minute are seldom larger or even as large as those found in some of the earlier minutes. While the figures show wide variations, the general picture which they convey is that the immediate effect of the work upon the ventilation was compensated for by the end of the third, or possibly the beginning of the fourth minute, and probably the ventilation reached approximate constancy by the time the subject had maintained a uniform rate of walking for 4 minutes. The ventila- tion during the periods on March 9 had a decided rhythmic effect which makes it uncertain whether or not on this day the effect of the work on the ventilation was offset by the third minute. This rhythm, however, is not apparent on any of the other days. CHANGES IN RATE OF OXYGEN CONSUMPTION (UNREDUCED). The changes in the rate of the oxygen consumption (unreduced) as the subject passed from standing to walking are shown in table 82. These include data for both standing and walking on March 9, 14, 15, 16, and 17, 1916. A few values obtained on February 24 are also given. TABLE 82. Rate of oxygen consumption of E. D. B. in periods of transition from standing to grade walking. Date, condition, and period of measurement. Oxygen consumption (unreduced) per minute. Period I. Period II. Period III. Period IV. March 9, 1916. Standing, measured in minutes c. c. 269 290 301 1,527 c. c. 269 280 290 1,484 c. c. 290 301 301 1,398 c. c. Walking; 30 p. ct.; av., 49 meters: Measured in }/% min. : 2d 301 301 1,527 3d 1,570 1,558 1,667 1,387 2,008 1,527 1,955 4th PHYSIOLOGICAL CHANGES IN TRANSITION. 285 TABLE 82. Rate of oxygen consumption of E. D. B. in periods of transition from standing to grade walking. Continued. Date, condition, and period of measurement. Oxygen consumption (unreduced) per minute. Period I. Period II. Period III. Period IV. March 9, 1916 cont'd. Walking, 30 p. ct. ; av. 49 meters cont'd. Measured in J^ min. cont'd. 5th c. c. 2,000 1,957 c. c. 1,978 1,935 c. c. 2,000 1,978 c. c. 2,021 2,107 6th 7th 1,828 2,020 1,729 2,494 2,247 2,236 8th 2,107 9th 2,021 2,043 2,193 2,107 2,064 2,116 2,236 2,261 10th llth 2,135 2,215 2,344 2,408 2,301 2,279 12th 2,086 13th 2,272 2,150 2,174 2,129 14th March 17, 1916. Standing, measured in minutes 312 323 269 258 237 280 344 258 312 344 376 312 269 312 290 333 301 247 Walking, 30 p. ct.; av., 53 meters: Measured in J^ min. : 1st 1,139 1,613 2d 1,312 1,462 1,247 3d 2,021 2,172 1,699 1,871 1,957 1,914 1,892 2,215 4th 5th 2,233 2,279 1,935 2,287 1,978 2,451 2,282 2,430 6th 7th 2,344 2,452 2,236 2,279 2,451 2,483 2,473 2,428 8th 9th 2,387 2,344 2,334 2,430 2,473 2,408 2,277 2,322 10th llth 2,335 2,344 2,408 2,322 March 14, 1916. Standing, measured in minutes 269 290 269 247 215 258 258 269 258 258 301 323 215 Walking, 30 p. ct.; av., 60 meters: Measured in J^ min. : 1st 301 333 237 258 1,288 1,441 2d 2,129 1,560 1,140 3d 1,957 2,057 1,828 2,322 1,914 2,258 1,806 2,150 4th 5th 2,561 2,752 2,580 2,462 2,262 2,449 6th 2,537 286 METABOLISM DURING WALKING. TABLE 82. Rate of oxygen consumption of E. D. B. in periods of transition from standing to grade walking Continued. Date, condition, and period of measurement. Oxygen consumption (unreduced) per minute. Period I. Period II. Period III. Period IV. March 14, 1916 cont'd. Walking, 30 p. ct. ; av. 60 meters cont'd. Measured in J^ min. cont'd. 7th c. c. 2,724 2,694 c.c. 2,473 2,469 c. c. 2,408 2,408 c.c. 2,494 2,551 8th 9th 2,666 2,494 2,437 2,484 2,365 2,795 2,693 10th March 15, 1916. Standing, measured in minutes 312 301 323 290 280 258 312 312 280 258 258 1,505 Walking, 30 p. ct.; av., 70 meters: Measured in j^ min. : 2d 323 323 258 1,871 1,548 3d 2,043 2,614 2,129 2,150 2,064 2,494 1,914 2,387 4th 5th 2,688 2,774 2,772 2,989 2,855 2,881 2,749 2,752 6th 7th 3,141 2,989 2,820 2,817 3,023 3,118 8th 3,075 9th 3,035 2,838 2,881 3,144 March 16, 1916. Standing, measured in minutes 333 355 355 344 312 290 366 258 Walking, 40 p. ct.; av., 66 meters: Measured in % min. : 1st 258 323 280 321 1,363 1,656 2d 1,697 1,957 1,937 3d 2,150 2,634 2,279 3,047 2,043 2,094 2,559 3,395 4th 5th 3,268 3,326 3,161 3,293 3,698 3,333 3,440 3,505 6th 7th 3,354 3,311* 3,419 3,611 3,483 8th February 4, 1916. Standing, av. of 3 minutes 287 556 560 649 874 835 Walking, 45 p. ct.; 45 meters: Measured in 1/5 min. : 1st 2d 3d 4th 5th 6th 1,207 1,364 1,530 7th 8th PHYSIOLOGICAL CHANGES IN TRANSITION. 287 The values for the oxygen consumption during standing are measured in minutes from the kymograph record during 3 or more of the 5 or 6 minutes preceding the tune of transition to walking. These unre- duced values for the oxygen consumption range somewhat about an average of 300 c. c. per minute. On March 16, especially in the first, second, and fourth periods, the respiration was uneven and the measurement of the kymograph curve was difficult. During the first 30 seconds of walking, the tracings were usually too irregular to determine the rate of oxygen consumption, but in the second half -minute we find the oxygen consumption was in almost every in- stance over 1,400 c. c., or from four to five times the standing require- ment. As a rule, in the third half-minute the oxygen consumption increased an additional 300 to 500 c. c., or a further increase of about one-quarter of that which occurred in the second half-minute. The values for the fourth half-minute are approximately of the same charac- ter as those hi the third half-minute, but with the increases over the preceding half-minute somewhat diminished. By the fifth half-min- ute, and certainly by the sixth half-minute (from 2\ to 3 minutes after the walking began), the oxygen consumption apparently reached a point indicating that the rate of consumption was commensurate with the body requirements for the work in hand. Beyond this point the rate of oxygen consumption remained essentially uniform for the re- mainder of the experimental period, irrespective of the amount of work being performed. REBPIKATORY CHANGES IN TRANSITION FROM GRADE WALKING TO STANDING. The respiratory changes during the transition from grade walking to standing were also measured in like manner as those for the transi- tion from standing to grade walking. (See fig. 38, p. 278.) The values for the respiration-rate and pulmonary ventilation are given in tables 83 and 84 and for the rate of oxygen consumption in table 85. In eight of these experiments the transition was measured during the final standing period after the subject had been walking during the preceding periods of the forenoon. The walking stopped simulta- neously with the beginning of the period and the respiration-rate and pulmonary ventilation were measured and compared with the average values for the preceding walking periods. (See table 83.) On only three of these days was an attempt made to estimate the oxy- gen consumption, and then only with the subject standing. On March 10 and 11, in addition to the preliminary walking, the subject walked 3 or 4 minutes of the period and then stood. Observa- tions for four periods were obtained on these two days. During these periods, the respiration, ventilation, and oxygen consumption were determined for both the walking and standing portions. (See tables 84 and 85.) The subject rested in the intervals between periods and 288 METABOLISM DURING WALKING. then had a preliminary walk in order to make the conditions as nearly alike as possible. CHANGES IN RESPIRATION-RATE. The respiration-rates during the walking periods show variations in the measurements per minute, but, on the whole, indicate what may be accepted as the average for walking in each period. A comparison of these rates with those obtained immediately after walking ceased shows that the respiration-rate falls during the first 12 seconds of stand- ing in all but three instances, i. e., February 14 and 15, and the second period of March 10. The decline is small in some cases, and none of the decreases exceed the rate of 6.5 respirations per minute, while the rate for the majority is less than 4 respirations per minute. In the suc- ceeding fractions of the first minute the records show increases and decreases without uniformity, although by the end of the minute the rates may possibly be said to be lower on the whole than at the begin- ning of the standing. The notable fact is that the change in respira- tion-rate is slight in the transition from walking to standing. Further- more, if 16 respirations per minute be taken as the normal respiration- rate for E. D. B. in the standing position, we find that in one or two instances this value is approached during the second or third minute after walking ceased, but the rate is not maintained. In nearly every case the rate is above the normal standing value during the fifth min- ute, while most of those records which extend into the seventh and eighth minutes show that the respiration-rate is still above the normal. This course is in contrast to the behavior of the respiration-rate in the transition from standing to walking, for the response under those con- ditions was largely within the first 12 seconds and a uniform rate had been attained by the end of the first minute of .walking. TABLE 83. Respiration-rate and pulmonary ventilation of E. D. B. in periods of transition from grade walking to standing. (Values per minute.) Date, condition, and period of measurement. Respi- ration- rate. Pul- monary venti- lation (unre- duced). Date, condition, and period of measurement. Respi- ration- rate. Pul- monary venti- lation (unre- duced). January 1, 1916. Walking, 20 p. ct.; 81.6 meters: Meas. in minutes 31.0 liters. 53.0 January 1, 1916 cont'd. Standing cont'd. Meas. in 1 /5 min. cont'd litert. 30 6 51 7 6th 25.0 30.4 Last full minute 27 6 54 2 7th 24.0 24.1 Standing: 8th 22.9 22.8 Meas. in 1/5 min. : 9th 18.5 18.3 1st 26 5 49 3 10th 22.2 19.0 2d 21 9 >c n 3d 26 5 35 1 llth 19.2 22.1 4th 26 5 35 4 12th 20.0 13.3 5th 21 8 25 6 13th 21.8 12.8 PHYSIOLOGICAL CHANGES IN TRANSITION. 289 TABLE 83. Respiration-rate and pulmonary ventilation of E. D. B. in periods of transition from grade walking to standing. (Values per minute.) Continued. Date, condition, and period of measurement. Respi- ration- rate. Pul- monary venti- lation (unre- duced). Date, condition, and period of measurement. Respi- ration rate. Pul- monary venti- lation (unre- duced). January 1, 1916 cont'd. Standing cont'd. Meas. in 1/5 min. cont'd. 14th 22 2 liters, 12 2 January S, 1916 cont'd. Standing cont'd. Following J^ min. cont'd. 5th 20 liters. 12 9 15th 20 3 11 1 6th 19 12.2 16th 17 9.9 February 12, 1916. 17th 14 7 10 4 Walking, 30 p. ct.; 74.6 18th 11 5 2 meters : 19th 18 2 8 9 Meas. in min 31.6 71.8 Following 1/2 min. : 1st 19.9 10.1 27.6 29.2 67.3 70.8 2d 20 7 10.8 29.2 70.4 28 7 71 3d 21 7 9 7 Last full minute 28.8 71.4 4th 19 9 10.9 Standing: 5th 19 3 10 8 1st 26.7 67.9 6th 18 9 9 6 2d 26 7 65.8 3d 28 1 55 January S 1916 4th 31 4 43.6 Walking 25 p. ct. ; 42.3 5th 26.7 37.0 Meas in minutes 24 30 1 6th 22.3 34.6 24 6 1 31 2 7th 26.7 28.5 23 2 32 6 8th 28.1 29.9 9th 26.2 30.6 Meas. in 1/5 min. : 10th 23.4 27.2 lof 99 ^ Qfl 4. 2d 20 9 25 1 llth 22.3 23.7 3d 17 1 20 2 12th 19.3 19.2 4th 20 21 1 13th 20.5 17.3 5th 25 7 21 14th 16.6 11.7 15th 18 6 10 9 RtVi 91 8 91 8 7th 19 2 16 8 16th 19.3 12.7 8th 21 8 16 2 17th 21.9 15.4 9th 20 14 2 18th 22.1 15.4 10th 20 9 15 5 19th 21.9 16.3 20th 21 9 15 8 llth on q 14 5 12th 20 15 21st 21.1 18.3 13th 19 2 13.4 Following 1/2 min. : 14th 15 8 12 5 1st 24.2 17.5 15th . ... 19 4 14 2d 19.8 17.4 16th . . . 19 4 12 3d 24.4 15.8 17th 21 12 8 4th 21.0 14.2 IRtVi 90 9 Hi Following 1/2 min: 5th 22.4 16.4 1st 21 3 13 5 6th 20.7 15.2 2H 20 12 8 7th 20 14 1 3d 20 4 13 5 8th 19.7 15.3 4th 18.4 12.3 290 METABOLISM DURING WALKING. TABLE 83. Respiration-rate and pulmonary ventilation of E. D. B. in periods of transition from grade walking to standing. (Values per minute.) Continued. Date, condition, and period of measurement. Respi- ration- rate. Pul- monary venti- lation (unre- duced) . Date, condition, and period of measurement. Respi- ration- rate. Pul- monary venti- lation (unre- duced). February 14, 1918. Walking, 30 p. ct.; 68.8 meters; Meas. in minutes 29.7 liters. 61.8 February 15, 1916 cont'd. Standing cont'd. Meas. in 1 /5 min. cont'd. 2d 34.1 liters. 45.5 27.6 63.4 3d 29.2 41.8 32.2 68.3 4th 29.2 28.7 25.9 61.3 5th 22.0 37 1 94 1 CO A Standing: 6th 26.4 31.2 Meas. in 1/5 min. : 7th 30.0 23.2 1st 30.7 75.2 8th 22.9 24.8 2d 29.6 63.7 9th 22.0 22.2 3d 29.6 56.2 10th 22.5 21.6 4th 30 7 43 7 6th 31.8 35.1 llth 21.9 16.1 12th 17 7 11 5 (5th 29.6 37.6 13th 16.9 10.5 7th 26.5 35.0 14th 18.9 12.3 8th 26.7 32.8 15th 15.4 8.4 Oth 26 5 26 5 10th 27.6 21.5 16th 21.2 15.8 17th 20 5 19 llth 21.6 12.6 18th 23.4 14.8 12th 19.7 12.8 19th 18.9 12.8 13th 21.2 18.9 20th 20.7 14.1 14th 23 8 17 3 15th 25 6 12 6 21st 20 7 12.8 22d 20 d 15 5 16th 25.9 14.1 23d 16.0 15.4 17th 24.6 17 2 24th 19.1 16.2 18th 24 15 8 25th 20.7 10.8 19th 24 6 19 3 20th 22.2 17.2 26th 24.0 15.3 27th 22 9 13 8 2lst 22 3 16.2 28th 24.0 14.5 22d 18 4 12 7 29th 24.0 21.2 23d 21.0 13.7 Following 1/2 min.: 24th . . . 20 3 11 6 1st 20.6 15.3 Following 1/2 min 2d 19.1 12.5 1st 19 3 15 3 2d 19.5 13.2 3d 21.6 14.6 4th 20 8 14 4 3d 20 7 13 8 4th 20.5 14.1 February 16, 1916. Wnltinir *\z> n r>t ^ft ft 5th 20.8 14.7 meters; 6th 19.6 13.9 Meas. in minutes 30.4 59.9 98 9 RQ A February IB, 1916. Last full minute 28.8 59.2 Walking, 35 p. ct.; 46.2 meters : Meas. in minutes 31.3 46 9 Standing: Meas. in 1/5 min. : 1st 28.4 51.4 29.8 46 9 2d 30.7 48.9 Last full minute 29.2 47 3d 27.1 43.5 Standing: 4th 26.4 35.4 Meas. in 1/5 min. : 5th 25.4 34.6 1st 34.1 54.2 PHYSIOLOGICAL CHANGES IN TRANSITION. 291 TABLE 83. Respiration-rate and pulmonary ventilation of E. D. B. in periods of transition from grade walking to standing. (Values per minute.} Continued. Date, condition, and period of measurement. Respi- ration- rate. Pul- monary venti- lation (unre- duced). Date, condition, and period of measurement. Respi- ration- rate. Pul- monary venti- lation (unre- duced) . February 16, 1916 cont'd. Standing cont'd. Meaa. in 1 /5 min. cont'd. 6th 25.4 25.4 27.6 24.0 24.0 liters. 30.6 19.5 21.3 24.1 22.0 February 17, 1916 cont'd. Standing cont'd. Meas. in 1 /5 min. cont'd. 13th 23.2 23.2 23.2 liters. 17.8 17.3 16.0 7th 14th. 8th 15th 9th 16th 10th 23.3 21.6 22.0 22.0 19.4 18.1 15.9 16.1 19.3 15.7 llth 17th 20.8 19.2 18.4 18.4 17.7 21.4 15.9 18.9 17.9 13.9 18th 12th 19th 13th 20th 14th Following 1/2 min.: 1st 15th 22.1 21.8 16.6 16.5 16th 13.3 16.9 20.8 22.7 20.0 9.4 13.4 14.8 14.5 14.0 2d 17th 3d 18th 19.9 20.4 16.0 13.5 19th 4th 20th Following minutes : 1st Following 1/2 min.: 1st 20.0 20.4 14.8 15.1 21.6 21.3 16.3 14.2 2d 2d February 25, 1916. Walking, 30 p. ct.; 59.6 meters: Last full minute 3d 32.0 25.5 22.1 22.2 20.9 17.8 50.3 44.0 33.5 27.9 21.4 19.4 19.4 19.5 14.6 13.5 4th 5th 20.5 22.7 13.2 15.7 6th Standing: Meas. in 1/5 min.: 1st February 17, 1916. Walking, 35 p. ct.; 62.5 meters : Meas. in minutes 30.0 27.2 28.5 29.3 29.0 24.8 29.7 30.3 29.7 23.6 69.5 67.1 69.8 71.8 71.2 57.0 52.1 44.1 46.4 42.7 2d 3d 4th Last full minute 5th 6th 17.1 21.0 22.0 14.7 13.2 16.0 17.8 13.5 10.3 9.9 7th Standing : Meas. in 1/5 min. : 1st 8th 9th 10th 2d llth 3d 17.2 20.5 18.8 20.2 13.3 13.2 11.9 14.5 10.3 7.1 4th 12th 5th 13th 6th 14th 28.4 22.6 21.7 19.8 21.7 25.3 27.6 20.8 18.4 19.9 15th . 7th 16th 8th 14.6 13.8 15.9 19.5 9.2 9.2 9.1 8.9 9th 17th . . . 10th Following 1/2 min.: 1st llth 23.2 21.1 19.0 18.5 12th 2d 292 METABOLISM DURING WALKING. TABLE 83. Respiration-rate and pulmonary ventilation of E. D. B. in periods of transition from grade walking to standing. (Values per minute.) Continued. Date, condition, and period of measurement. Respi- ration- rate. Pul- monary venti- lation (unre- duced). Date, condition, and period of measurement. Respi- ration- rate. Pul- monary venti- lation (unre- duced) . February 5, 1916 cont'd. Standing cont'd Following 1 /2 min. cont'd. 3d 18.0 liters. 9.4 February 86, 1916 cont'd. Standing cont 'd. Following 1 /2 min. cont'd. 9th liters. 4th 17.3 9.9 10th 12 8 8 4 5th 16 8 8.6 llth 12 9 9 1 6th 15.4 9.3 12th 14.4 9.9 7th 16 8 13th 13 6 9 9 8th 17.3 9.4 TABLE 84. Respiration-rate and pulmonary ventilation of E. D. B. in successive periods of transition from grade-walking to standing (Values per minute.) Date, condition, and period of measurement. Period I. Period II. Period III. Period IV. Respi- ration- rate. Pul- monary venti- lation (unre- duced). Respi- ration- rate. Pul- monary venti- lation (unre- duced). Respi- ration- rate. Pul- monary venti- lation (unre- duced). Respi- ration- rate. Pul- monary venti- lation (unre- duced). March 10, 1916, Walking, 30 p. ct.; av., 53.3 meters: Measured in minutes 26.4 30.4 30.8 30.4 33.3 27.1 26.8 31.7 24.8 22.0 liters. 56.5 73.1 68.6 71.2 74.7 52.2 44.7 40.2 27.4 23.9 liters. liters. liters. Last full minute 28.7 30.3 28.0 30.5 32.1 30.8 29.5 28.7 28.7 60.7 76.0 61.7 72.4 74.2 64.0 51.7 46.3 36.9 30.0 29.7 32.3 32.3 28.5 24.1 22.4 23.2 31.2 61.7 75.5 76.6 76.1 54.8 39.1 28.5 22.5 27.7 30.8 30.2 33.3 32.4 28.1 24.6 23.6 24.6 22.7 60.3 72.6 66.4 72.9 52.3 44.0 39.8 33.4 24.7 Standing, measured in 1/5 min. : 1st 2d 3d 4th 5th 6th 21.4 19.3 21.2 18.7 22.4 20.3 18.7 19.0 17.1 19.1 17.9 23.3 18.5 17.4 19.2 16.3 19.9 15.7 13.4 13.4 32.0 24.2 22.3 21.1 23.2 30.1 28.0 21.7 15.8 18.8 25.8 23.0 23.5 23.9 26.7 20.9 19.7 17.7 19.0 18.4 7th 8th 9th 10th Following 1/2 min.: 1st 20.2 18.4 18.2 17.0 21.2 21.6 16.4 17.3 23.6 22.8 18.0 18.0 20.9 22.0 19.1 17.4 2d 3d 19.7 17.7 18.0 18.4 23.6 20.5 18.5 19.2 21.6 21.7 17.8 18.4 23.7 21.7 18.9 18.2 4th PHYSIOLOGICAL CHANGES IN TRANSITION. 293 PABLE 84. Respiration-^rate and pulmonary ventilation of E. D. B. in successive periods of transition from grade walking to standing. (Values per minute.) Continued. Date, condition, and period of measurement. Period I. Period II. Period III. Period IV. Respi- ration- ' rate. Pul- monary venti- lation (unre- duced). Respi- ration- rate. Pul- monary venti- lation (unre- duced). Respi- ration- rate. Pul- monary venti- lation (unre- duced). Reapi- ration- rate. Pul- monary venti- lation (unre- duced). March 10, 1916 cont'd. Standing cont'd. Following 1/2 min. cont'd. 5th 18.2 16.7 liters. 18.5 18.2 19.2 21.6 liters. 17.9 18.6 20.0 21.6 liters. 18.0 18.4 21.1 18.2 liters. 19.1 15.0 6th 7th 19.8 17.3 20.1 14.3 20.2 17.8 8th March 11, 1916. Walking, 30 p. ct.; av., 62.6 meters: Measured in minutes 27.0 28.0 27.2 29.7 25.0 22.7 26.8 27.2 25.2 52.2 63.4 63.2 61.7 47.1 44.8 27.8 24.3 25.8 31.0 32.0 32.5 31.6 25.7 27.0 26.7 28.8 22.2 56.2 71.2 67.7 63.8 42.8 34.3 27.7 27.4 22.2 31.3 31.9 32.2 30.8 24.3 22.7 21.8 19.9 19.9 59.0 72.2 64.5 68.6 46.3 34.0 26.8 23.3 18.5 30.2 31.4 29.5 32.0 27.1 23.4 23.4 24.4 20.3 56.9 67.6 67.1 62.8 50.6 41.0 31.1 28.9 21.2 Last full minute Standing, measured in 1/5 min. : 1st 2d 3d 4th 5th 6th 22.8 21.1 18.2 18.9 18.8 20.9 17.3 14.7 15.7 15.7 22.5 23.2 22.2 20.4 20.3 19.1 20.1 18.9 17.7 17.0 18.5 24.8 33.5 23.1 19.1 15.3 23.0 22.2 21.2 14.3 20.0 16.8 27.3 19.7 20.6 23.0 13.3 14.6 20.2 16.4 7th 8th 9th 10th Following J^ min. : let 19.4 20.8 14.3 16.6 20.3 20.4 17.1 16.8 21.3 19.6 16.6 16.4 20.2 20.2 13.9 15.9 2d 3d 18.9 20.6 14.8 15.6 20.4 17.3 17.7 15.0 19.0 19.4 14.9 15.3 21.1 21.8 15.3 16.1 4th 6th 20.1 18.5 15.4 13.8 20.1 18.7 16.6 16.0 20.9 21.3 16.1 16.4 20.9 22.0 15.8 17.0 6th 7th 18.0 17.2 14.4 14.6 19.7 16.3 21.8 18.0 20.3 14.6 8th CHANGES IN PULMONARY VENTILATION. The response to the lessened demands of the body indicated by changes in the pulmonary ventilation on the cessation of walking is very noticeable and different in this respect from the results found for the respiration-rate. In the first 12 seconds of standing, the pulmo- nary ventilation fell in all but three instances and in amounts from 1 to 23 liters. This decrease continued throughout the first and second minutes, and usually longer. By the end of the first minute the fall 294 METABOLISM DURING WALKING. TABLE 85. Rate of oxygen consumption of E. D. B. in periods of transition from grade walking to standing. Date, condition, and period of measurement from transition. Oxygen consumption (unreduced) per minute. Period I. Period II. Period III Period IV. January 1, 1916, Standing, measured in 1/5 min.: 2d c.c. c. c. c. c. c.c. 2.150 1 1,720! 1,82s 1 1,505! 2,596 2,649 1,429 2,662 1,630 1,278 3d 4th 5th February 14, 1916. Standing, measured in 1/5 min. : 2d 3d 4th February 17, 1916. Standing, measured in 1/5 min.: 2d 3d 4th March 10, 1916. Walking, 30 p. ct.; av., 63.3 meters: Measured in minutes: 5th 1,870 1,862 2,279 2,220 2,226 4th 1,861 2,162 2,625 2,182 1,909 2,005 2,243 2,599 1,935 1,670 2,118 2,658 3d 2d 1st Standing, measured in 1/5 min.: 1st 2,580 2,473 1,935 1,505 1,129 2,311 2,258 ,2,311 2,795 2,795 2,150 1,075 2,473 2,096 2,043 1,881 1,451 2d 3d 4th 5th 1,398 6th 860 753 484 484 376 1,236 753 753 699 538 591 1,129 914 645 7th 8th 645 538 484 9th 10th 430 Following 1/2 min.: 1st 366 430 452 344 516 430 452 409 2d 3d 387 366 344 387 409 344 409 452 4th 5th 280 452 409 387 344 6th 445 7th 421 1,910 1,984 2,354 2,779 344 2,023 1,971 2,290 2,324 March 11, 1916. Walking, 30 p. ct.; av., 52.6 meters: Measured in minutes: 4th 1,838 1,884 2,022 2,169 2,199 1,949 2,172 2,389 3d 2d 1st 'Period V. PHYSIOLOGICAL CHANGES IN TRANSITION. 295 TABLE 85. Rate of oxygen consumption of E. D. B. in periods of transition from grade walking to standing Continued. Date, condition, and period of measurement from transition. Oxygen consumption (unreduced) per minute. Period I. Period II. Period III. Period IV. March 11, 1916 cont'd. Standing, measured in 1/5 min.: 1st c. c. 2,365 2,365 c. c. 2,311 1,989 c. c. 3,064 2,688 1,720 1,236 1,075 c. c. 2,473 2,903 1,881 1,236 968 2d 3d 4th 6th 1,021 914 6th 806 645 538 484 484 860 645 645 484 430 968 645 699 591 591 645 7th 8th 9th 484 538 10th Following 1/2 min. : 1st 387 366 452 387 473 452 538 473 2d 3d 366 323 387 366 409 430 452 387 4th 5th 344 344 366 366 387 344 387 409 6th 7th 301 301 266 445 8th had amounted to 40 to 60 per cent of the ventilation during walk- ing. If the normal ventilation of E. D. B. for the standing position be taken as 11 liters per minute (unreduced), as would appear to be the case from the values in table 81, it is seen that this value was approached in a number of instances in the third minute after walk- ing ceased. These values are not maintained in most of the cases, but are succeeded by a higher ventilation, from which it begins slowly to fall. In most of the records, however, the ventilation appears to be in the region of 15 liters per minute and to be still above the nor- mal standing value after 5 minutes of standing. On but three days (January 1 and 3, and February 25) does the ventilation appear to be adjusted to the pre- walking value before the end of the measurements. This would indicate that the body was striving to eliminate the large excess of carbon dioxide previously formed in the work of walking. CHANGES IN RATE OP OXYGEN CONSUMPTION (UNREDUCED). Comparison measurements of the unreduced oxygen consumption during standing and walking experiments were made from the kymo- graph records on March 10 and 11, 1916, only. These measurements, which, immediately after the transition, were made in one-fifth min- utes, are recorded in table 85. A few measurements of the oxygen con- 296 METABOLISM DURING WALKING. sumption during standing were also made on January 1, February 14 and 17, 1916. These results are likewise included in table 85, and show that during the first minute of standing after walking ceased there was a contraction in the oxygen consumption ranging from 600 to 1,400 c. c. between the second and the fourth or fifth fractions of the first minute. No measurements were made for the first one-fifth min- ute of standing on account of irregularities in the record, and no measurements of the oxygen consumption during walking on these dates are available for the transition period. Any real comparison must therefore be confined to the two days for which we have more nearly complete data. The results for March 10 and 11, 1916, include both walking and standing values for four periods on each d#y. The first point which attracts attention is the fact that the oxygen consumption during the first two one-fifth minute measurements for standing usually indicates an increase over the walking rate. The tracings in this portion of the transition record were always irregular at their low points, implying that the transition disturbed the normal type of respiration. It is thus difficult to determine the course of the rise in these few seconds, since an error of 2 mm. represents approximately 80 c. c., and a few disturbed respirations at this point could easily introduce an error of double this amount hi the probable course. This disturbance presumably rep- resented a temporary alteration hi the residual air in the lungs. It is only after these first disturbances have passed that the true change taking place in the oxygen consumption is apparent. This point was reached by the third or fourth one-fifth minute, when the fall amounted to approximately 400 or 500 c. c. By the end of the first minute the oxygen consumption had fallen to approximately one-half of the values found with the subject walking. The drop from this point is almost uniformly progressive during the second minute and continues with somewhat less regularity to the end of the measurement. If, from the data in table 82, the normal unreduced oxygen consumption of E. D. B. for the standing position be taken as 280 c. c. per minute, it is seen that in only two cases is there an approach to this figure by the end of the measurement (see March 10, period 1, and March 11, period 3); that is, during the time that these measurements were extended (5 or 6 minutes), the oxygen consumption continued above the normal stand- ing requirements. It is also seen that, after the first unreliable readings due to a disturbed record, the fall was approximately uniform. CONCLUSIONS REGARDING RESPIRATORY CHANGES IN TRANSITION FROM GRADE WALKING TO STANDING AND THE REVERSE. From these measurements it is thus found that during the period of transition from standing to walking, the respiration-rate responded within 12 seconds and the maximum change was over by the end of the first minute; that the pulmonary ventilation responded within the first 12 seconds to double the standing value, and continued increasing through the third minute, while the oxygen consumption increased PHYSIOLOGICAL CHANGES IN TRANSITION. 297 4 to 5 times within the first minute and the increase was practically over within 3 minutes. Under reverse conditions, i. e., in the transi- tion from walking to standing, the respiration-rate fell slowly and irregularly and was not settled nor at its normal value within 8 minutes. The ventilation-rate fell promptly and within 1 minute was one-half of the value found with the subject walking, this decrease continuing, but with diminishing force; after 8 minutes of standing it was still above the normal. The oxygen consumption was in harmony with the pul- monary ventilation, failing continuously but not reaching a pre- walking normal value during the 6 minutes of measurement. PULSE-RATE IN TRANSITION FROM STANDING TO GRADE WALKING. In the comparison of the pulse-rate for the standing position with that in grade walking (see p. 262), it was seen that the rate in the walk- ing periods increased largely, the size of the increases depending upon the amount of work done. The results are given graphically in figures 30 to 32, inclusive, pages 265 to 267. The duration of the preliminary walking before the experimental period began varied somewhat, but was rarely, if ever, less than 5 minutes, and in most cases more nearly 15 minutes. During this preUminary walking it was assumed that the metabolism and physiological factors had become adjusted to the new demand and that the body functions were acting on a constant, though higher, plane. This assumption was confirmed by the general picture for the respiration, ventilation, and oxygen consumption previously discussed. (See pp. 278 to 287.) The new level in these cases was reached by or before the fourth minute of exercise, and most of the change occurred inside of 1 minute after the exercise began. To obtain some estimate of the alterations which take place in the pulse-rate during the time of change from quiescence to grade walking, a number of electro-cardiograms were made for E. D. B. in the period extending from one-half minute before the grade walking began through the first or second minute of exercise. In addition, some records were made in the change from walking to standing at the end of the experi- mental period. These changing pulse-rates have been termed the transition pulse- rates. To express the rapid alteration in the heart-action under these conditions, we have used the duration of the pulse-cycle. While the most desirable method of recording these changes would naturally be to have the time-intervals on the photographic paper of such size that each pulse-cycle could be readily measured in 0.01 second, the labor and the tune involved precluded any extended use of this method. It should be remembered that in all this work our interest was in the pulse-rate and, as explained on page 34, the electro-cardiogram was used simply as a means of determining that factor and not to study the type or peculiarities of the pulse-cycle. On two occasions (Feb- ruary 28 and 29) the paper was run through the camera with such rapidity that it was possible to measure the durations of the individual cycles. Ordinarily, however, the rate of movement was so adjusted 298 METABOLISM DURING WALKING. that the pulse-rate per minute could be easily counted, but the time- intervals on the paper were too small for the accurate measurement of the duration of the individual pulse-cycle. Therefore, in order to have our period of measurement long enough to secure reasonably accurate readings to 0.01 second, the cycles were measured in groups of 10. The results given accordingly represent the average duration of a pulse-cycle as calculated from the measurement of the time re- quired for a group of 10 pulse-cycles. The changes in the average duration as thus determined give a clearer measure of altering heart- rate than could be obtained by the usual method of counting the pulse. The changes in the duration of the pulse-cycle in the transition from standing to walking are shown in the four curves in figure 39. In this figure each point on the abscissa represents the average of 10 consecu- tive pulse-cycles, while the duration of the pulse-cycle is given in 0.01 second as the ordinate. The pulse-rates equivalent to the measured durations are shown on the right. As the duration of the cycle is changing, the time required for a group of cycles also changes, but the approximate elapsed times are indicated for groups of 100 cycles by email figures and inclusion marks below the curves. The point at which the subject began to walk is shown on the curve by the letter X. 030t ;i.oo ' t.io {-- c A if 1 f M CL neir / / I . ,,m* ISO 120 too 84 76 87 1 55 at 50 2 tOO 100 200 300 100 PULSE CYCLES O tOO 200 300 tOO 100 200 100 100 200 300 FIQ. 39. Duration of pulse-cycles of E. D. B. in transition from standing to grade walking, as indicated by average cycle duration for measured groups of 10 pulse-cycles. Beginning of walking at X. A, Feb. 18; B, Feb. 21; C, Feb. 19; D, Feb. 22. The time required for groups of cycles, varying in number, is indicated by email figures and inclusion marks at the bottom of the charts. The cycles to the left of X accordingly represent measurements for the standing position and to the right those for grade walking. The average grades and speeds used in the walking are indicated for each curve. In figure 39, a noticeable feature is the wide variation in the duration of the pulse-cycles while the subject was standing, as shown by the variability of the portion of each curve at the left of X. The measure- ments for the standing position were made with the same degree of accuracy as those obtained during the walking, and there is no reason to doubt the presence of these wide differences. Measurements of PHYSIOLOGICAL CHANGES IN TRANSITION. 299 similar character, which were made subsequent to this work and re- ported by Benedict, Miles, Roth, and Smith, 1 showed like irregularities which were explained by the investigators as due in all probability to a psychical stimulus occasioned by the warning signal for starting. Though no signal for starting was given in the experiments here rep- resented, the explanation may apply to these curves also, for the sub- ject was naturally conscious that walking would begin at any moment, as there were certain routine movements which he would recognize as preceding the start. These irregular factors of duration have one noticeable feature in common, namely, one or more points of a retarded pulse, i. e., of lengthened duration. It does not appear that the lengthening was in any way related to the beginning of walking, though one might expect that it marked the period when the subject realized that the operator was ready to open the air-valve and start the treadmill. It is also apparent from these curves that the average cycle duration shortened uniformly during walking to a minimum duration which was reached in from 150 to 200 cycles, the greater portion of this change occurring in the first 100 cycles, with the change gradually diminishing. On two days (see curves A and B), a slight tendency to a reaction set in at approximately 100 cycles. The time when the minimum dura- tion was reached is seen to be approximately 1 minute and, except in curve C, this minimum was held with a considerable degree of con- stancy in the remainder of the record, i. e., to the end of the second minute. It is thus evident that the pulse-rate increased to meet the demand of the added work placed upon the body within approximately 150 cycles and with a time lapse of between 1 and 2 minutes. Beyond this point there would undoubtedly be some rise and some variation, but the greater part of the pulse change occurred in the first minute for the conditions of work illustrated here. To compare the pulse-cycles over greater intervals of tune, a more extended record of five curves is given in figure 40. In these records we have attempted to measure the individual cycles and each point represents the average of 2 cycles thus measured. Since under these conditions there is more or less error in the estimation of fractions of time intervals, not a little of the irregularity shown in the pulse-cycles for standing may be due to this cause. Curve A in figure 40 is a record taken during the middle of a standing period at 9 h 44 m a. m. on Feb- ruary 28, 1916. Even allowing for the errors of measurement, it is evident that during standing there were constant fluctuations in the duration of the pulse-cycle like those found in the standing portions of the curves in figure 39. Between the minimum and maximum dura- tions there was a total difference of 0.34 second, this change occurring within 8 cycles. The second curve (B), which is not continuous with curve A, includes the transition from standing to walking. Like the curves in figure 39, the standing portion, which is indicated by the re- Benedict, Miles, Roth, and Smith, Carnegie Inst. Waah. Pub. No. 280, 1919, p. 429. 300 METABOLISM DURING WALKING. versed numbering of the groups of cycles, shows similar irregularities and marked lengthening in the deration of the cycles previous to the beginning of walking at X. The rise in the curve subsequent to the beginning of walking was decided and regular for 20 cycles, or approxi- mately 15 seconds. Thereafter the rise was more gradual, and after 1 minute of walking the rate was fairly uniform at 0.45 second. Curve C is a record taken after the walking had been in progress for 2 minutes and covers a period of approximately 1 % minutes. During most of this time the pulse-cycle was between 0.5 and 0.4 second in duration, shortening slightly with the time and ending at 0.4 second. 0.30 .40 1.00 1.10 1.20 10 20 30 40 20 PULSE CYCLES 10 20 30 40 50 60 70 80 90 100 110 120 130 FIG. 40. Duration of pulse-cycles of E. D. B. in grade-walking experiment of Feb. 28, 1916, as indicated by averages of 2 pulse-cycles, measured individually. A, standing; B, transition standing to walking; beginning of walking at X; C, D, and E, walking after 2, 26, and 30 minutes, respectively, of continuous walking. Curves D and E with lengthened record of time-interval. The time required for groups of cycles, varying in number, is indicated by small figures and. inclusion marks below each curve. After the subject had been walking continuously 26 minutes, a record was taken in which the photographic paper was put through the camera at a rate of approximately 5 cm. a second, which produced a space interval between the pulse-cycles of from 12 to 15 mm. This permitted measurements with a greater degree of accuracy, the results being given in curves D and E. As in the other curves, the points represent the averages of 2 cycles. The durations of the pulse-cycles PHYSIOLOGICAL CHANGES IN TRANSITION. 301 shown in curve D are practically constant, varying from 0.44 to 0.48 second throughout a record of three-quarters of a minute, thus indi- cating a more uniform duration of the pulse-cycle than that shown by curve C. The second record taken by this method (curve E) was made after a total period of walking of 30 minutes. During the 144 cycles in this curve, the length of cycle varied only from 0.37 to 0.39 second. These two records show a remarkably constant cycle duration after a sufficient period of time had elapsed for the body to become adjusted to the needs of the exercise of walking. While they 0,50, .60 .70 .80 .90 .30 .40 .50 ,60 3.70 J j .80 3 ? .90 A. ' N .1.00 wo 1 1.20 15' 10 20 30 * 40 PULSE CYCLES 50 30 20 10 10 20 30 40 50 60 70 80 90 100 110 FIG. 41. Duration of pulse-cycles of E. D. B. in grade-walking experiment of February 29, 1916, as indicated by averages of two pulse-cycles measured individually. A, standing; B, transition standing to walking, beginning of walking at X. C, walking 26 min- utes after X. D and E, standing 8 and 14 minutes, respectively, after end of walking. All curves except B with lengthened record of time-interval. The time required for groups of cycles, varying in number, is indicated for curve B by email figures and inclusion marks at the bottom of the chart. also indicate that the irregularities in the duration of the pulse-cycle in the few seconds preceding walking may in part be due to errors of measurement, it is believed, for reasons given later, that these irregu- larities are present, and that the relative behavior of the pulse for stand- ing and walking as shown by the curves in figure 40 is correct. 302 METABOLISM DURING WALKING. Figure 41 gives 5 curves of the duration of the pulse-cycles on Feb- ruary 29, each point, as in figure 40, being the average of 2 cycles. Curve A represents pulse-cycles with the subject standing in the second period of the day, and exhibits like variations to those referred to in the discussion of other curves. In the corresponding curve A of figure 40, although the individual pulse-cycles were measured, the time-intervals on the photographic paper were small, and it was suggested that some of the irregularities in the curve may have been due to errors of measure- ment. In curve A of figure 41, however, the time-interval was lengthened and this source of error was thus largely removed, but the same variation in the pulse-cycles for standing is apparent. The maximum variations during this record are as large as 0.4 second, with 0.3 second as the greatest difference between two successive points. In curve B, the time-interval was not lengthened and the errors in estimating the fractions of a second are therefore greater. The stand- ing portion of the curve, as in the curves earlier discussed, shows gross variations in the cy )le duration. On the transition to walking there is a lengthening of pulse-cycle duration which is directly at variance with the other records given in figures 39 and 40. The question may fairly be raised if the time of transition were correctly indicated on the photographic paper and if it may not have been a second or two later. As in the preceding figures, the major portion of the rise in the curve had taken place by the measurement of the fortieth or fiftieth cycle, with an average cycle duration at that tune of 0.5 second. Thereafter, the change in the duration was but slight, reaching an approximate value of 0.45 second at the end of the curve, which covers a time-inter- val of 65 seconds. After the subject had been walking 26 minutes, a short record was made (curve C) in which the tune-intervals on the record were lengthened by increasing the speed of feeding the paper to the camera. It may be noted that in this curve (C), the duration of the pulse-cycle had further shortened to 0.36 to 0.39 second, and there is less variation between the readings. This is in harmony with curves D and E of figure 40, which illustrated the regularity of the pulse-cycle duration after a continued period of exercise. Curves D and E in figure 41 will be considered subsequently, as they represent records taken when the man was standing after walking. From these measurements of the durations of the pulse-cycle in the transition from standing to grade walking, there is evidence that the standing pulse varied widely between successive cycles; that the inter- val preceding walking is likely to be influenced by psychical effects due to the anticipation of the starting of the treadmill; that most of the rapid shortening of the cycle duration after the beginning of walking occurs within 25 or 30 cycles, or about 15 to 20 seconds, and is over within 1 minute; and that the shortening of the duration thereafter is very gradual and may continue for a period of 25 to 30 minutes. PHYSIOLOGICAL CHANGES IN TRANSITION. 303 PULSE-RATE IN TRANSITION FBOM GRADE WALKING TO STANDING. The changes in the duration of the pulse-cycle occurring when the subject stopped walking and stood are shown in curves D and E in figure 41 and also in four curves in figure 42. Curve D hi figure 41 represents the records obtained after the subject had stood 8 minutes. Like curve C in the same figure, this record was made with the time- intervals lengthened by an increase in the speed of the paper through the camera, and is thus largely free from errors of measurement. During this record there was difficulty with the feed of the paper at the points indicated by the broken lines, and the record is not continuous for 5 to 7 seconds on account of the slipping of the feed- rolls and overexposure of the paper. Notwithstanding this, the record shows that the duration of the cycle had lengthened from the walking duration of 0.4 second to approximately 0.6 second, and, further, that the variations of a standing pulse had begun to appear, which have already been noted in previous discussion of figure 40 and of curve A in this figure. Curve E is similar to but not continuous with curve D, and repre- sents the pulse measured with lengthened time-intervals after the subject had been standing for 14 minutes. A wide variation in the duration of cycles is seen in the curve, but this variation differs from that in the other standing records, as here a pronounced rhythm is present, occurring with each 12 to 14 cycles. At first thought it might be said that this rhythm was connected with the respiration, but assuming the average pulse-cycle duration in the curve is 0.73 second, the time-intervals for the rhythm would be nearly 10 seconds, corresponding to a respiration-rate of 6 respirations per minute. As seen in table 86 (p. 306), the average respiration-rate 24 minutes after walking ceased on February 29 was 16.9, and it is unlikely that it could have approached the rate required by the estimated length of the rhythm. The record was made during the middle of the period, when conditions were free from any disturbances which might have a tendency to stimulate or retard the pulse-cycle. The cause of the evident rhythm remains unexplained. The changes in the duration of the pulse-cycle after walking ceased are also shown in the four curves in figure 42. These curves are con- structed in the same way as those in figure 39, each point indicating the average duration of a pulse-cycle as calculated from the measure- ment of a group of 10 cycles, and each square in the figure representing 100 cycles. The ordinates, however, have been drawn to a larger scale than in figure 39. The variations in the pulse-cycles thus appear larger than hi the curves in figure 39. In curve A the duration of the pulse-cycle for the subject walking is between 0.33 and 0.34 second. During the first 50 cycles following the transition, the duration lengthened to 0.36 second, with a total 304 METABOLISM DURING WALKING. lengthening of but 0.02 to 0.03 second. In the next 50 cycles there was a further fall in. the curve to 0.42 second, and by the end of 150 cycles the duration was between 0.45 and 0.46 second, or a lengthening of the cycle of but little more than 0.1 second. This is in decided con- trast to the rapid rate of change shown in the transition from standing to walking, when most of the change occurred within 100 cycles. The 150 cycles of curve A occupied approximately 1 minute, and the following minute brought the duration to but 0.49 second. The return of the cycle duration during the first few minutes of standing is there- fore slow in comparison to the transition in the change from standing to walking. 0.30 ^K % D 186 176 167 158 100 143 36 30 25 Sj 20 jroa \ \ \ \ r I s i 5 HI / i 2(50 1OO 100 200 300 200 100 100 200 300 1OO 1OO 20O 30O PULSE CYCLES FIG. 42. Duration of pulse-cycles of E. D. B. in transition from grade walking to stand- ing, as indicated by average cycle duration for measured groups of 10 pulse-cycles. Beginning of standing at Y. A, Feb. 12; B, Feb. 14; C, Feb. 17; D, Feb. 15. The time required for groups of cycles, varying in number, is indicated by small figures and inclusion marks at the bottom of each chart. The behavior of the pulse-cycle in curve B is almost the same as that found in curve A. The duration just previous to the transition is practically the same. At the end of 100 cycles the duration has lengthened to 0.42 second, or but 0.08 second. At 150 cycles, occupy- ing approximately 60 seconds, the duration was about 0.46 second. Two minutes of standing resulted in a total lowering of the duration of the pulse-cycle 0.12 second. This curve shows some lag at the transi- tion which other curves do not show. In curve C the duration of the pulse-cycle lengthened from 0.33 second preceding the transition to standing to 0.37 second in 50 cycles, while in 150 cycles after the walking ended, occupying approximately 60 seconds, the duration lengthened to 0.44 second, or a total lengthen- ing of 0.11 second. This rate of lengthening agrees with that found in the two preceding curves, namely, in 150 cycles of approximately 60 seconds of elapsed tune, the change in the average duration of the cycle was but little over 0.1 second, and by the end of 2 minutes the AFTER-EFFECTS OF GRADE WALKING. 305 lengthening of the duration of the cycle did not reach 0.2 second. The duration of the pulse-cycle at the end of 2 minutes is thus less than 0.5 second, or, in terms of pulse-rate per minute, the change has been from 176 to 125 beats. Curve D is composed of 5 records, covering a duration of 147 seconds, and therefore is not continuous. Consequently, it must be considered on a time basis rather than according to the number of consecutive pulse-cycles. For the first 70 cycles the record was continuous and the elapsed time was 30 seconds. In this time the duration lengthened to about 0.41 second, or a total lengthening of 0.06 second. At the end of 1 minute the duration fell another 0.01 second, and at the end of the record, after 2 minutes and 27 seconds of standing, the duration of the pulse-cycle was 0.49 second, or 0.14 second longer than at the transi- tion. At the end of 1 minute or thereabouts, all four of these curves begin to exhibit a marked irregularity in the duration of the pulse- cycles, similar to that seen for the pulse during standing in figures 39, 40, and 41, with some suggestion of a rhythm in curves A and C, recalling that seen in curve E in figure 41. From these curves it appears that the response to the change from walking to standing is rapid, although slightly slower than with the change from standing to walking; also, that the lengthening of the pulse-cycle after walking had ceased continues at a uniform rate for approximately a minute, during which time the rate decreases from 40 to 50 beats a minute. After the immediate drop in the first minute, the change apparently becomes less marked, with wide fluctuations in the cycle durations. AFTER-EFFECTS OF GRADE WALKING. As a part of the routine of the research, a few standing experiments were made with E. D. B. following periods of grade walking, for a study of the after-effects of the exercise on the standing metabolism. The results are compared in table 86, in which the average pre- walking values for the day are taken from table 6 and the grade-walking values are drawn from table 16. In each case the length of the period of walking, with the grade and the speed, also the length of period of rest (sitting) between the walking and standing observations, are given in table 86. As the values for December 21, 1915, to February 17, 1916, inclusive, were obtained immediately after walking ceased, they naturally represent rapidly changing values, especially hi the earlier part of the period. The experiments of February 26 to 29, inclusive, have three post- walking periods each, with an interval of rest, i. e., sitting, of approxi- mately 20 to 24 minutes before the measurements in the first standing period began . The last period on each of these days was approximately 2 hours after walking. The changes in these last periods would 306 METABOLISM DURING WALKING. TABLE 86. Metabolism of E. D. B. when standing after grade walking in experiments without food. (Values per minute.) Date and experimental conditions. 1 Aver- age respira- tion- rate. Aver- age pul- monary venti- lation (re- duced). Aver- age pulse- rate. Aver- age body- tem- pera- ture. Carbon dioxide. Oxy- gen. Respi- ratory quo- tient. Heat (com- puted). Dec. 21, 1915: Standing before walking 14 8 liters. 8 9 58 C. c. c. 190 c. c. 207 92 cals. 1 02 Walking l^O ; 20 p. ct., 70 m. p. m. . . 26.0 37.0 1,596 1,784 .90 8 78 Standing, no rest 18.3 105 322 380 .85 1 85 Dec. 22, 1915: Standing before walking 12.8 8 190 218 87 1 07 Walking I h 34 m ; 20 p. ct., 70 m. p. m. . . 25.7 34 2 1,554 1,748 .89 8 59 Standing, no rest 19 5 13 6 102 307 367 84 1 78 Dec. 31, 1915: Standing before walking 15 2 9 7 75 211 257 82 1 24 Walking I h 2 ra ; 20 p. ct., 80 m. p. m. . . 27.6 43.9 2,042 2,270 .90 1.18 Standing, no rest 22.2 16 2 128 405 490 .83 2 37 Jan. 3, 1916: Standing before walking 15.6 9 5 210 250 .84 1 21 Walking I h 39 m ; 25 p. ct., 43 m. p. m. . . 23 8 29 1 1,183 1,451 .82 7 00 Standing, no rest 19 2 12 5 284 352 81 1 69 Feb. 12, 1916: Standing before walking 14.4 8 8 65 36.80 191 244 .78 1.17 Walking l h ; 30 p. ct., 72 m. p. m Standing, no rest 28.4 21.6 59.6 18 4 163 122 37.75 2,471 455 2,613 528 .95 .86 13.03 2 57 Feb. 14, 1916: Standing before walking 14 9 9 2 77 37.10 196 240 82 1 16 Walking l h ; 30 p. ct., 68 m. p. m Standing, no rest 27.8 22.1 54 5 17 8 166 123 37.98 38.50 2,311 417 2,481 511 .93 .82 12.31 2.47 Feb. 15, 1916: Standing before walking 16.2 10 1 79 36.94 207 261 .79 1.25 Walking I h 21 m ;35p. ct., 45m. p. m.. . Standing, no rest 27.7 21 1 40.5 14 9 145 125 38.29 38.53 1,732 369 2,007 452 .86 .82 9.78 2 18 Feb. 16, 1916: Standing before walking 15.5 9.4 36.88 205 255 .80 1.22 Walking 19 ; 35 p. ct. , 58 m. p. m Standing, no rest 29.6 20.9 54.5 15 8 174 131 38.27 2,267 382 2,495 476 .91 .80 12.32 2.29 Feb. 17, 1916: Standing before walking 16 5 10 85 37.13 210 267 .79 1.28 Walking 57" ; 35 p. ct. , 62 m. p. m Standing, no rest 29.1 21.3 61.8 16.7 177 122 38.08 38.51 2,507 424 2,725 520 .92 .82 13.48 2.51 Feb. 26, 1916: Standing before walking 16.1 9.4 70 37.01 212 251 .84 1.22 Walking I h 4 m ; 30 p. ct., 69 m. p. m Standing after 24 m rest 30.2 16 7 54.6 9.7 153 96 37.61 38.13 2,387 210 2,592 273 .92 .77 12.83 1.30 Standing, I h 18 m after walking 2 . . . . 16 7 9 5 81 37.22 206 245 .84 1.19 Standing, 2 h 8 m after walking 2 16.1 9.1 73 36.71 210 267 .79 1.28 Feb. 28, 1916: Standing before walking 15.1 9.1 69 36.74 213 244 .87 1.19 Walking I h 2 m ; 30 p. ct., 67 m. p. m Standing after 20" 1 rest 30.2 15.4 55.0 10.0 150 101 37.11 38.09 2,374 239 2,508 282 .95 .85 12.50 1.37 Standing, I h 15 m after walking 2 15.6 9.6 83 37.30 223 252 .88 1.23 Standing, I h 55 m after walking 2 16.6 9.9 80 37.19 218 266 .82 1.28 Feb. 29, 1916: Standing before walking 14.8 8.8 68 36.70 183 230 .80 1.10 Walking 34 m ; 30 p. ct., 69 m. p. m. . . Standing after 24 m rest 32.1 16 9 56.5 10 3 153 37.44 38.04 2,284 213 2,491 291 .92 .73 12.33 1.37 Standing, l h l m after walking 2 15.9 9.4 88 37.18 198 276 .72 1.30 Standing, I h 50 m after walking 2 16.3 9.5 82 36.83 191 245 .78 1.17 1 The values for standing before walking and for grade walking are average values for the day. and 16, pp. 46 and 78. Those for standing after walking are period values. 2 During this interval between the walking and standing, the subject sat for a part of the time. AFTER-EFFECTS OF GRADE WALKING. 307 naturally be less, and it might be expected that values of approximately the pre-walking rate would be found. In experimental periods con- tinuing as long as those employed by us in this study it was naturally not expected that the measurements would show the gradations that could be obtained by other methods; nevertheless a general comparison may be made of the metabolism preceding and following walking. In the experiments of December 21 to February 17, inclusive, it is seen that the data for the respiration, ventilation, and pulse show no close approach to the pre-walking values since they were obtained immediately on the cessation of walking. It may be noted, however, that although the percentages vary, the ventilation-rate remained at a higher level, relatively, than the respiration-rate, the former averaging approximately 70 per cent above the pre-walking average and the respiration-rate approximately 40 per cent. In the first of the post-walking periods of February 26 to 29, fol- lowing 20 or more minutes of rest, both respiration and ventilation, though much reduced, were still above the pre-walking values. In the third standing period, which was approximately 2 hours after walking had ceased, the data for February 26 show that the respira- tion-rate and pulmonary ventilation had fallen to the pre-walking rate during the interval, but that on February 28 and 29 these factors were still above the pre-walking averages. The pulse remained above the pre-walking rate on all of these days. This is in keeping with the re- sults reported by Benedict and Cathcart, 1 who found that the pulse- rates did not readily return to the pre-walking level after such pro- longed exercise. Only a few measurements of the body-temperature are available for comparison, but these are included in table 86. The post-walking temperatures appear here to be higher than those obtained in the walking periods. This is contrary to the curves in figures 33 to 37. inclusive, which show a rapid fall in body-temperature after walking ceased. This difference in direction is due to the fact that the temper- ature values for walking given in table 86 represent averages of all the walking periods of the day, and thus no sharp comparison of the walk- ing and standing values is possible here. The special interest in this connection is, however, the comparison between the temperatures with the subject standing before and after walking. It is seen that for the periods of standing immediately after walking, the average body-temperature is 1.5 C. higher than the pre-walking tempera- ture and for the first post-walking periods on the days when a rest interval of but 24 minutes intervened the difference is but little less. By the second post-walking period, the temperatures are still nearly 0.5 C. above the pre-walking temperature. It is not until the third Benedict and Cathcart, Carnegie Inst. Wash. Pub. No. 187, 1913, p. 153. 308 METABOLISM DURING WALKING. period, representing a time-interval of 2 hours after walking ceased, that the temperature may be said to approximate anything like the original values. The after-effects of exercise on the gaseous exchange have recently been studied by Campbell, Douglas, and Hobson, 1 and by Krogh and Lindhard, 2 who followed the changes through brief intervals. These authors find, in harmony with Zuntz, with Benedict and Cathcart, and with others, that the respiratory quotient increases when the work stops; after a brief period it falls to a value somewhat below normal. The values here reported for 15-minute periods do not, of course, show the stimulated respiratory quotient for the post-walking periods which, according to Krogh and Lindhard, occurs approximately 1| minutes after the end of walking. In the standing periods follow- ing immediately after the cessation of walking (December 21 to February 17), the respiratory quotient is lower than during the walking period, and but little different from the pre-walking quotients. This is probably explained by the fact that the quotients for a period fol- lowing immediately the cessation of walking would be influenced by the high values referred to above as occurring for a short time. It is only when the periods are taken after the temporary high respiratory quotients have passed that the after-effects of walking become evident. All of the post- walking periods of February 26 to 29 on which there was an interval of rest following the walking indicate a lowered respi- ratory quotient in relation to both the pre-walking and the walking respiratory quotients. On two of these days the subject had walked somewhat over an hour and on the last day about half that tune. Campbell, Douglas, and Hobson conclude that the possible presence of lactic acid in the muscles is alone not sufficient to explain the be- havior of the respiratory quotient following the cessation of work and are inclined to believe with Zuntz and with Benedict and Cathcart that the probable explanation is that during the period of walking the glycogen reserve in the body is depleted and that during the subse- quent periods proportionally less carbohydrate than fat is consumed in the body metabolism. A rough estimate of the amounts of glycogen consumed during 1 hour of walking on the basis of an oxygen consumption of 2,500 c. c. per minute and a respiratory quotient of 0.90 is as follows: The total energy produced in 1 hour would be approximately 750 calories; if 60 per cent of this energy were derived from carbohydrate to produce the respiratory quotient of 0.90, as assumed by Magnus-Levy, 3 and 4.23 calories be assumed as the heat-production from 1 gram of gly- cogen, the total amount of glycogen consumed in 1 hour of walking 'Campbell, Douglas, and Hobson, Phil. Trans., London, 1920, Ser. B, 210, p. 1. 2 Krogh and Lindhard, Journ. Physiol., 1920, 53, p. 431. 3 Magnus-Levy, in von Noorden's Handbuch der Pathologie des Stoffwechsels, Berlin, 2d ed., 1906, 1, p. 207. SUMMARY OP RESULTS. 309 would be somewhat over 100 grams, i. e., more than one-fourth of the amount believed to be present normally in the body. Benedict and Cathcart 1 report low respiratory quotients 5 hours after exercise, and Zuntz and Schumburg 2 maintain that the carbohydrate reserve was not established with their subject until the following day. The stimulating effect of walking is also seen from the experiments of February 26 to 29, in that the gaseous metabolism remained above the pre-walking values even after a lapse of 2 houis following the cessa- tion of walking. Only on February 26 did the metabolism reach the pre-walking values in the case of the carbon dioxide, for on both of the other days the carbon dioxide was still slightly above standing normal requirements at the end of the observations. The oxygen consumption, which is the best index of the metabolism, was above the pre-walking requirements by approximately 7 per cent after the lapse of 2 hours. SUMMARY OF RESULTS. In the preceding pages it has been found that the average standing metabolism obtained with the subjects studied was 1.18 calories per kilogram of body-weight per hour, or 28.4 calories per 24 hours. (See table 19.) This, when compared with average metabolism for the lying position of 25.3 calories per kilogram of body- weight per 24 hours (see table 17), represents an increase for the standing position of 12 per cent. When the standing requirements are used as a basis, it is found that the increase in the energy expended in horizontal walking over the energy output for the standing position varied for the 8 subjects from 0.454 to 0.618 gram-calorie for each horizontal kilogrammeter, i. e., the transportation of 1 kilogram a distance of 1 meter hi a hori- zontal direction. For the two subjects W. K. and E. D. B., with whom most of the work in this research was done, the increase for the horizontal walking in the energy expended was 0.490 and 0.478 gram- calorie, respectively, for each horizontal kilogrammeter. These values are below the average value used by other investigators, but show good agreement. The total energy expended per meter increase in speed was not measurably affected until a speed of 80 meters a min- ute was reached, beyond which point each meter increase in speed required a proportionately greater increase in the energy consump- tion. (See table 37.) In grade walking the total heat expended increased uniformly per kilogrammeter of work performed at each grade, but was somewhat less when the same amount of work was derived from a high grade and a low speed than when due to a low grade and high speed. (See figs. 21 and 22.) The total outlay was from 15 to 12 gram-calories per kilo- grammeter for amounts of work ranging from 300 to 600 kg. m. per Benedict and Cathcart, Carnegie Inst. Wash. Pub. No. 187, 1913, p. 172. 2 Zuntz and Schumburg, Physiologic des Marsches, Berlin, 1901, p. 255. 310 METABOLISM DURING WALKING. minute, and from 12 to 10 gram-calories per kilogrammeter when the work was between 1,000 and 1,500 kg. m. per minute. (See also table 62.) The average increment in the heat-output due to grade walking was approximately 7.5 gram-calories per kilogrammeter of work per- formed. From the results of this study it may be said that the net efficiency with which a person can walk up-grade is not far from 30 per cent when the work is under 500 kg. m. per minute, but when the work amounts to more than 500 kg. m. per minute, the efficiency decreases as the work increases. (See table 69.) The measurements of the pulmonary ventilation during grade walk- ing show that the increase in this physiological factor for each increase of 100 kg. m. of work was from 3 to 5 liters, while the total percentage increase with excessive work was as much as 850 per cent above the standing requirement. (See tables 76 and 77.) This enormous in- crease indicates the wide margin which must be provided in designing gas-masks to be worn during excessive muscular work. During grade walking, the respiration-rate for the subject E. D. B. showed constant increase over the standing value of 1.2 respirations for each 100 kg. m. increase in the work when over 500 kg. m. of work was done. With the subject W. K. the increase over the standing res- piration-rate was more nearly 2 respirations per 100 kg. m. (See tables 74 and 75.) The percentage increase over the standing rate was from 8 to 10 per cent for W. K., while for E. D. B. the increase was as high as 40 per cent for the first 100 kg. m., but fell rapidly with increase in the amount of work and became constant at approximately 8 per cent. In horizontal walking the pulse-rate frequently was less than that with the subject standing, even with an increase in the metabolism of 100 to 200 per cent. During grade walking, the pulse-rate showed a practically uniform increase with the increase in the amount of work performed. The increment in the pulse-rate over the rate found for the standing position rose rapidly with the increase in the work performed ; though the percentage increase per 100 kg. m. of work remained fairly constant, considerable differences were shown between individuals. (See tables 78 and 79.) The body- temperature showed increases as high as 2 C., indicat- ing for a body-weight of 60 kilograms a storage of heat in the body of approximately 100 calories. From the measurements taken at the time of transition from stand- ing to grade walking, it is believed that in most cases the body adjusts itself to the new demands as to pulse, respiration -rate, pulmonary ventilation, and oxygen-supply by the end of the third minute, and by far the larger part of the adjustment has occurred within 30 sec- onds. The recovery after exercise, however, is not so prompt, and the after-effects of the walking persist for a much longer time before initial conditions are reestablished. 7770 THE UNIVERSITY LIBRARY UNIVERSITY OF CALIFORNIA, SANTA CRUZ SCIENCE LIBRARY This book is due on the last DATE stamped below. To renew by phone, call 429-2050 RK'D JAW 2 o 198J 30m-9,'72(Q4585s8) 3A-1 m *%*&* Z&*^* QP301.S7 Sci 3 2106 00259 7448