id	author	title	date	pages	extension	mime	words	sentences	flesch	summary	cache	txt
en-wikipedia-org-6765		Heart rate - Wikipedia			.html	text/html	9680	1092	65	Although attributed to various sources, it is widely thought to have been devised in 1970 by Dr. William Haskell and Dr. Samuel Fox.[26] Inquiry into the history of this formula reveals that it was not developed from original research, but resulted from observation based on data from approximately 11 references consisting of published research or unpublished scientific compilations.[27] It gained widespread use through being used by Polar Electro in its heart rate monitors,[26] which Dr. Haskell has "laughed about",[26] as the formula "was never supposed to be an absolute guide to rule people's training."[26]	./cache/en-wikipedia-org-6765.html	./txt/en-wikipedia-org-6765.txt