key: cord-0019236-189z788q
authors: You, Min; Laborde, Sylvain; Zammit, Nina; Iskra, Maša; Borges, Uirassu; Dosseville, Fabrice; Vaughan, Robert S.
title: Emotional Intelligence Training: Influence of a Brief Slow-Paced Breathing Exercise on Psychophysiological Variables Linked to Emotion Regulation
date: 2021-06-20
journal: Int J Environ Res Public Health
DOI: 10.3390/ijerph18126630
sha: b24f8cc76e36e3d7bbb8414fb14ef50833775644
doc_id: 19236
cord_uid: 189z788q

Designing emotional intelligence training programs requires first testing the effectiveness of techniques targeting its main dimensions. The aim of this study was to investigate the effects of a brief slow-paced breathing (SPB) exercise on psychophysiological variables linked to emotion regulation, namely cardiac vagal activity (CVA), as well as perceived stress intensity, emotional arousal, and emotional valence. A total of 61 participants completed a 5-min SPB exercise and a control condition of a 5-min rest measurement. CVA was indexed with the root mean square of successive differences (RMSSD). Participants were also asked to rate their perceived stress intensity, emotional arousal, and emotional valence. Results showed that CVA was higher during SPB in comparison to the control condition. Contrary to our hypothesis, perceived stress intensity and emotional arousal increased after SPB, and perceived emotional valence was less positive after SPB. This could be explained by experiencing dyspnea (i.e., breathing discomfort), and the need to get acclimatized to SPB. Consequently, we may conclude that although physiological benefits of SPB on CVA are immediate, training may be required in order to perceive psychological benefits.

Athletes experience a large range of emotions during competition [1] . Emotions can be considered as short-lived psychological states, but some more stable emotional dispositions can also be identified [2, 3] . One of them is emotional intelligence (EI), which reflects the way individuals deal with their own and others' emotions [4, 5] . Emotional intelligence plays an important role in sport performance [6, 7] , and hence its training is of high relevance for athletes. The aim of this paper is to investigate whether a brief slow-paced breathing (SPB) exercise without biofeedback could be integrated into EI training, based on its effects on psychophysiological variables linked to emotion regulation.

The theoretical foundations of EI have evolved to include its different aspects via the tripartite model [8] , including the knowledge, ability, and trait levels. The knowledge level reflects what people know about emotions (e.g., knowing that SPB may help them

The way individuals perceive their stress and emotions is highly relevant for emotion regulation [2, [60] [61] [62] . However, a research gap exists regarding the potential influence of SPB on subjective psychological states related to emotion regulation in athletes. Hence, addressing subjective psychological states such as perceived stress intensity, emotional arousal, and emotional valence is of high relevance for athletes, given their influence in sport [1, 11, 63, 64] as well as in other life domains, such as the academic [65] or the professional [66] domains. The subjective effects of SPB have received little attention so far [67] [68] [69] [70] . On the one hand, previous research [68, 69] focusing on using SPB for the treatment of panic attacks implemented clinically focused self-report instruments. On the other hand, Van Diest, Verstappen, Aubert, Widjaja, Vansteenwegen and Vlemincx [67] showed that healthy participants reported higher pleasantness and lower arousal after a 5-min SPB exercise. Nonetheless, Allen and Friedman [70] noted that SPB can provoke dyspnea (i.e., the perception of uncomfortable breathing), and showed that presenting positive pictures during SPB reduced dyspnea [71] . Given these mixed findings, our study aimed to clarify the influence of SPB on self-report variables linked to emotion regulation.

To sum up, the current study aims to address research gaps found in previous literature, by investigating the effects of a brief (5-min) SPB exercise on CVA and subjective psychological variables linked to emotion regulation, namely perceived stress, emotional arousal, and emotional valence. Based on the literature reviewed, we hypothesize that, in comparison to the control condition, the brief SPB exercise would trigger an increase in CVA. However, due to the mixed findings reported so far regarding subjective states linked to SPB, we investigated this aspect in an exploratory manner.

This study was part of a larger research project investigating the effects of SPB without biofeedback in athletes. The analyses presented here have not been used or published elsewhere. Sample size determination followed recommendations for HRV research [51, 72] . A total of 66 athletes were recruited as participants. Exclusion criteria were self-reported cardiovascular diseases, and other chronic diseases that might influence breathing or HRV patterns, such as asthma, diabetes, psychiatric, and neurological diseases [51] . Due to technical issues, the data of 5 participants had to be excluded, and the final sample comprised 61 athletes (M Age = 22.1, age range = 18-30 years old; 25 female; BMI: M = 23.21, SD = 2.17; Waist-to-hips ratio: M = 0.81, SD = 0.08; number of sport hours per week: M = 7.5 h; SD = 3.3). The experimental protocol was approved by the Ethics Committee of a German University (Project Identification Code 06/11/2014).

HRV was measured with an ECG device (Faros 180 • , Bittium, Kuopio, Finland), at a sampling rate of 500 Hz. Two disposable ECG pre-gelled electrodes (Ambu L-00-S/25, Ambu GmbH, Bad Nauheim, Germany) were used. The negative electrode was placed in the right infraclavicular fossa (just below the right clavicle) while the positive electrode was placed on the left side of the chest, below the pectoral muscle in the left anterior axillary line. From ECG recordings, RMSSD was extracted using Kubios (University of Eastern Finland, Kuopio, Finland). The ECG signal was visually inspected for artefacts and these were corrected manually when deemed necessary (<0.001% of the heartbeats), as recommended [51] . To provide an overview of the different HRV parameters [51] , we also extracted the heart frequency and the standard deviation of the NN interval (SDNN) for the time-domain. For the frequency-domain (Fast Fourier Transform) low-frequency (LF; 0.04 to 0.15 Hz), high-frequency (HF: 0.15 to 0.40 Hz), and the LF/HF ratio were calculated for descriptive purposes only.

Similar to previous research (e.g., [58, 73] ), SPB was conducted with a video showing a ball moving up and down at the rate of 6 cpm, based on the EZ-Air software (Thought Technology Ltd., Montreal, Canada). Participants were instructed to inhale continuously through the nose while the ball was going up, and exhale continuously through the mouth with pursed lips when the ball was going down. The video displayed a 5-min SPB exercise, with inhalation lasting 4 s and exhalation 6 s, given a longer exhalation is suggested to trigger higher increases in CVA [67, 74] .

A visual analogue scale (VAS), consisting of a 100 mm vertical line, was used to assess perceived stress intensity. The line was anchored by the words "not stressed at all" at the extreme left of the line, and "extremely stressed" at the extreme right of the line. Participants were required to indicate their perceived stress intensity by crossing a corresponding point somewhere on the line. The value of the perceived stress intensity was represented by the distance in mm from the extreme left of the line. Previous research has implemented this scale to assess perceived stress intensity [16, 75, 76 ].

The self-assessment manikin [77] assesses the emotional state of an individual along two dimensions, valence and arousal (we did not include the third dimension, control, given it did not fit the aim of our study). The self-assessment manikin is a picture-oriented instrument containing five images for each of the two affective dimensions that the participant rates on a 9-point scale. Valence is depicted from negative (a frowning figure) , to neutral, to positive (a smiling figure) . Higher scores reflect consequently a more positive valence. Arousal is depicted ranging from low arousal (eyes closed) to high arousal (eyes wide open), with higher scores representing higher arousal.

Participants were recruited through flyers on the campus of the local university as well as via posts on social network groups linked to the local university. In line with recommendations for psychophysiological experiments involving HRV measurements [51] , participants were instructed to follow their usual sleep routine the night prior to the experiment, not to consume alcohol or engage in strenuous physical activity in the previous 24 h, nor to drink or eat 2 h before taking part in the experiment. All participants gave written informed consent before participation, and were informed that they could withdraw from the study at any time without any explanation or consequence. The participants had to come to the lab once, for a within-subject design. After being welcomed to the lab, they were asked to fill out an informed consent form and a demographic questionnaire regarding variables potentially influencing HRV [51, 53, 78] . The ECG device was attached, and participants went through a 15-min familiarization video to get acquainted with SPB. Participants had then to go through two conditions in a counterbalanced order: (1) SPB condition: 5-min baseline, 5-min SPB, 5-min recovery; (2) control condition: 5-min baseline, 5-min rest, 5-min recovery. HRV was measured continuously throughout, and all measurements were performed with eyes opened. Participants filled out the self-report items at the end of each 5-min period. At the end of the session, the ECG device was detached, and participants were thanked and debriefed.

HRV variables were exported from the Kubios output. Data were checked for normality and outliers. Regarding outliers, 0.01% of the cases were found to be univariate outliers (>2 SD). Their exclusion from the analyses did not change the pattern of results, therefore they were retained in the final analysis. As the RMSSD data was not normally distributed, a log-transformation was applied, as recommended for HRV research [51] .

We conducted a series of repeated-measures ANOVAs, with time (baseline, intervention/rest, recovery) and condition (SPB vs. control) as independent variables, and respectively RMSSD, perceived stress intensity, perceived emotional arousal, and perceived emotional valence as dependent variables. Based on our hypotheses, we focused specifically on the time x condition interactions.

Descriptive statistics are presented in Table 1 for all study variables. For RMSSD (see Figure 1 ), a repeated-measures ANOVA with Greenhouse-Geisser correction was conducted and showed a significant main effect of time F(1.456, 97.385) = 51.370, p < 0.001, partial η 2 = 0.46; a significant main effect of condition F(1, 60) = 36.825, p < 0.001, partial η 2 = 0.38, and a significant time x condition interaction effect F(1.709, 102.567) = 60.478, p < 0.001, partial η 2 = 0.50. Nine follow-up post hoc t-tests were conducted, adjusting alpha level with Bonferroni correction to 0.006 (0.05/9). RMSSD was higher for in the SPB condition when participants performed SPB in comparison to the rest control measurement, t(60) = 12.553, Cohen's d = 1.61, p < 0.001. In the SPB condition, RMSSD was higher during the SPB exercise, in comparison to before t(60) = 13.158, Cohen's d = 1.69, p < 0.001; or after the SPB exercise, with t(60) = 12.722, Cohen's d = 1.63, p < 0.001. No differences were found between the different measurement times of the control condition, nor across conditions between the measurements before and after SPB/rest control. For perceived stress (see Figure 2 ), a repeated-measures ANOVA with Greenhouse-Geisser correction was conducted and showed a significant main effect of time F(1.676, 100.589) = 8.535, p < 0.001, partial η 2 = 0.13; a significant main effect of condition F(1, 60) = 18.385, p < 0.001, partial η 2 = 0.24, and a significant time x condition interaction effect F(1.506, 90.363) = 16.656, p < 0.001, partial η 2 = 0.22. Nine follow-up post hoc t-tests were conducted, adjusting alpha level with Bonferroni correction to 0.006 (0.05/9). Perceived stress was higher in the SPB condition after SPB in comparison to after the rest control measurement, t(60) = 7.160, Cohen's d = 0.92, p < 0.001. In the SPB condition, perceived stress was higher after the SPB exercise, in comparison to after pre-rest t(60) = 5.343, Cohen's d = 0.69, p < 0.001; or post-rest, with t(60) = 6.172, Cohen's d = 0.79, p < 0.001. No differences were found between the different measurement times of the control condition, nor across conditions between the measurements before and after SPB/rest control. For perceived stress (see Figure 2) , a repeated-measures ANOVA with Greenhouse-Geisser correction was conducted and showed a significant main effect of time F(1.676, 100.589) = 8.535, p < 0.001, partial η 2 = 0.13; a significant main effect of condition F(1, 60) = 18.385, p < 0.001, partial η 2 = 0.24, and a significant time x condition interaction effect F(1.506, 90.363) = 16.656, p < 0.001, partial η 2 = 0.22. Nine follow-up post hoc t-tests were conducted, adjusting alpha level with Bonferroni correction to 0.006 (0.05/9). Perceived stress was higher in the SPB condition after SPB in comparison to after the rest control measurement, t(60) = 7.160, Cohen's d = 0.92, p < 0.001. In the SPB condition, perceived stress was higher after the SPB exercise, in comparison to after pre-rest t(60) = 5.343, Cohen's d = 0.69, p < 0.001; or post-rest, with t(60) = 6.172, Cohen's d = 0.79, p < 0.001. No differences were found between the different measurement times of the control condition, nor across conditions between the measurements before and after SPB/rest control. For perceived stress (see Figure 2) , a repeated-measures ANOVA with Greenhouse-Geisser correction was conducted and showed a significant main effect of time F(1.676, 100.589) = 8.535, p < 0.001, partial η 2 = 0.13; a significant main effect of condition F(1, 60) = 18.385, p < 0.001, partial η 2 = 0.24, and a significant time x condition interaction effect F(1.506, 90.363) = 16.656, p < 0.001, partial η 2 = 0.22. Nine follow-up post hoc t-tests were conducted, adjusting alpha level with Bonferroni correction to 0.006 (0.05/9). Perceived stress was higher in the SPB condition after SPB in comparison to after the rest control measurement, t(60) = 7.160, Cohen's d = 0.92, p < 0.001. In the SPB condition, perceived stress was higher after the SPB exercise, in comparison to after pre-rest t(60) = 5.343, Cohen's d = 0.69, p < 0.001; or post-rest, with t(60) = 6.172, Cohen's d = 0.79, p < 0.001. No differences were found between the different measurement times of the control condition, nor across conditions between the measurements before and after SPB/rest control. For perceived emotional arousal (see Figure 3) , a repeated-measures ANOVA with Greenhouse-Geisser correction was conducted and showed a significant main effect of time F(1.818, 109.065) = 7.735, p < 0.001, partial η 2 = 0.11; a significant main effect of condition F(1, 60) = 9.421, p = 0.004, partial η 2 = 0.13, and a significant time x condition interaction effect F(1.559, 93.519) = 19.604, p < 0.001, partial η 2 = 0.25. Nine follow-up post hoc t-tests were conducted, adjusting alpha level with Bonferroni correction to 0.006 (.05/9). Perceived emotional arousal was higher in the SPB condition after SPB in comparison to the control condition after the rest control measurement, t(60) = 6.798, Cohen's d = 0.87, p < 0.001. In the SPB condition, perceived emotional arousal was higher after the SPB exercise, in comparison to after pre-rest t(60) = 5.557, Cohen's d = 0.71, p < 0.001; or post-rest, with t(60) = 5.233, Cohen's d = 0.67, p < 0.001. No differences were found between the different measurement times of the control condition, nor across conditions between the measurements before and after SPB/rest control. ceived emotional arousal was higher in the SPB condition after SPB in comparison to the control condition after the rest control measurement, t(60) = 6.798, Cohen's d = 0.87, p < 0.001. In the SPB condition, perceived emotional arousal was higher after the SPB exercise, in comparison to after pre-rest t(60) = 5.557, Cohen's d = 0.71, p < 0.001; or post-rest, with t(60) = 5.233, Cohen's d = 0.67, p < 0.001. No differences were found between the different measurement times of the control condition, nor across conditions between the measurements before and after SPB/rest control. 

The aim of this study was to investigate the effects of a brief SPB exercise on CVA and subjective psychophysiological variables, to understand its potential role within EI 

The aim of this study was to investigate the effects of a brief SPB exercise on CVA and subjective psychophysiological variables, to understand its potential role within EI training programs. Our hypothesis regarding CVA was confirmed, given an increase was found in comparison to the control condition. Regarding the subjective variables, findings showed that the 5-min SPB was perceived as more stressful, with higher emotional arousal, and with more negative valence than the resting control condition. These findings are explained below in accordance with current literature in the field.

Regarding CVA, our findings are in line with previous literature, given so far a robust increase in CVA has been systematically demonstrated during SPB, while returning to levels close to baseline when ceasing the SPB exercise [55, [57] [58] [59] . This acute increase may occur due to the action of SPB on the baroreflex [41] and on pulmonary afferents [38] , thus stimulating the vagus nerve [39, 42] . The novelty of the current findings resides in the fact that previously the increase in CVA during SPB had been mostly documented with longer SPB practice times of 15-min [55, [57] [58] [59] , while a 5-min SPB exercise was used in the current study. The fact that CVA returns to baseline after SPB would reflect the cessation of vagus nerve stimulation. However, increases in CVA found at rest after long-term SPB interventions (30 days, 15-min per day) would suggest that the regular stimulation of the vagus nerve via SPB leads to chronic increases in CVA. The underlying mechanisms still need to be uncovered, but we can speculate at this stage that those announced earlier, involving the functioning of the baroreflex, of pulmonary afferents, and the effects on brain networks involved in emotion regulation may certainly play a role in these chronic adaptations [36, [38] [39] [40] [41] [42] Our results regarding the subjective experience revealed that the 5-min SPB exercise was perceived as more stressful, with higher emotional arousal, and with more negative valence than the resting control condition. These results appear contradictory to those of Van Diest, Verstappen, Aubert, Widjaja, Vansteenwegen and Vlemincx [67] , who found that a similar 5-min SPB exercise, with an approaching inhalation/exhalation ratio (3 s inhalation and 7 s exhalation, in comparison to 4 s inhalation and 6 s exhalation in our study), decreased perceived emotional arousal and increased perceived emotional valence in comparison to a baseline condition with spontaneous breathing, while they did not report any change in perceived stress intensity. These results are quite surprising, given the same instrument, the self-assessment manikin [77] , was used to assess perceived emotional valence and perceived emotional arousal. We may speculate that in our study participants might have been experiencing dyspnea and found the breathing uncomfortable, potentially due to hyperventilation or unusual additional strain on the respiratory muscles. Previous research has documented dyspnea in individuals performing SPB [70, 79] , and have suggested the use of positive emotion induction (e.g., pictures linked to positive emotions) to counteract the potential discomfort triggered by SPB. Specifically, Allen and Friedman [70] instructed participants to inhale when a black screen appeared, and exhale when the positive pictures appeared, consequently linking positive pictures to the activation of the parasympathetic nervous system. The control condition did not include the positive pictures, but only displayed HRV-biofeedback. The authors found that dyspnea was rated as less unpleasant and less intense with positive pictures compared to the condition with HRV-biofeedback. Consequently, future research may consider using this strategy to decrease potential dyspnea, and control more strictly that participants adopt a shallow breathing technique, to avoid hyperventilating and decrease the solicitation on the respiratory muscles. Finally, future research designs may consider testing the effects of multi-sessions interventions, given the repeated realization of slow-paced breathing appears to improve participants' experience [80] . The use of relaxing music or sounds may also help to improve participants' experience.

Our study had some strengths, but also some limitations. Future studies should investigate whether participants are hyperventilating by using a capnometer to measure end-tidal carbon dioxide (e.g., [81] ). Increased tidal volume may also have triggered more strain on respiratory muscles, and this should be controlled in further research. Addi-tionally, given different sports contribute differently to CVA [82] , future research should consider the type of sport practiced by athletes when interpreting the results of slow-paced breathing. Finally, it should be noted that we focused here on SPB without using a biofeedback device. The use of SPB has so far mostly been realized with biofeedback, showing associations with a large range of positive physical and mental health outcomes [83] . In sports, SPB with biofeedback has been associated with improved performance [84, 85] . However, given biofeedback requires the use of additional devices to display the live biological signal, it is less accessible to people from lower socioeconomic backgrounds and in developing countries. Importantly, so far there is no evidence that SPB performed with biofeedback induces different physiological (CVA) or subjective (state anxiety) changes than when realized without [86] . Our results show that positive physiological benefits can be achieved using SPB without biofeedback, as indicated by increases in CVA. However further research should investigate whether the subjective experience of the participant differs between both modalities.

To conclude, the aim of this study was to investigate the use of SPB without biofeedback on CVA and self-report parameters linked to emotion regulation, to understand its unique added value within EI training programs. Findings showed that while CVA increased in the SPB condition, self-report measures displayed a more contrasted effect for emotion regulation, with increased perceived stress and emotional arousal, and more negative emotional valence. Altogether, these findings suggest that SPB had a positive influence at the physiological level; however, participants may have experienced some discomfort implementing this breathing technique. Consequently, future research and applied implementation of SPB should consider these findings by instructing participants not to hyperventilate, and potentially adding positive pictures to the SPB exercise [70, 79] .

Despite contrasting findings related to the subjective experience, findings regarding CVA are particularly relevant to consider, due to its role in emotion regulation and overall self-regulation [46, 51, [87] [88] [89] [90] [91] ]. CVA appears consequently as a relevant physiological marker to index the effectiveness of techniques used in EI training programs. In athletes, higher CVA was found to be associated with better executive functioning and coping under pressure [16, [92] [93] [94] [95] [96] [97] . Given SPB has been shown to improve both CVA and executive functioning in athletes [55, 57, 59] , it appears to be a promising technique for the applied field. Despite the existence of other techniques which stimulate the vagus nerve without requiring the active attention of the individual, such as transcutaneous vagus nerve stimulation [98] [99] [100] , the advantage of SPB is that it does not require any device, representing a suitable low-cost, low-technology, and non-pharmacological way to stimulate the vagus nerve.

Among the techniques already integrated into EI training that target the activity of the autonomic nervous system, SPB appears consequently to be a suitable candidate for emotion regulation, even if the instructions have to guarantee that the subjective experience aligns with the physiological benefits. Consequently, based on our findings, and taking into account several aspects that may increase the subjective experience, we may recommend implementing SPB within EI training programs. Future research should investigate whether the long-term use of SPB as a performance habit [101] , as previously implemented in athletes [56] , could also lead to stable changes in EI, as measured with EI questionnaires [102] , such as the Trait Emotional Intelligence Questionnaire [4, 103] or the Profile of Emotional Competences [5] . 

Feelings in Sport-Theory, Research, and Practical Implications for Performance and Well-Being

How emotions influence performance in competitive sports

Trait personality in sport and exercise psychology: A mapping review and research agenda

Technical Manual for the Trait Emotional Intelligence Questionnaire (TEIQue)

The Profile of Emotional Competence (PEC): Development and validation of a self-reported measure that fits dimensions of emotional competence theory

Emotional intelligence in sport and exercise: A systematic review. Scand

The influence of emotional intelligence on performance in competitive sports: A meta-analytical investigation

Going beyond the ability-trait debate: The three-level model of emotional intelligence an unifying view: The three-level model of EI

Trait emotional intelligence and preference for intuition and deliberation: Respective influence on academic performance

Culture, individual differences, and situation: Influence on coping in French and Chinese table tennis players

Validity of the trait emotional intelligence questionnaire in sports and its links with performance satisfaction

Relationship between emotional intelligence and anxiety in a futsal club from Madrid

Anxiety and emotional intelligence: Comparisons between combat sports, gender and levels using the trait meta-mood scale and the inventory of situations and anxiety response

Relationship between emotional intelligence and anxiety levels in athletes

Trait emotional intelligence in sports: A protective role against stress through heart rate variability?

The contribution of coping-related variables and heart rate variability to visual search performance under pressure

The role of trait emotional intelligence in emotion regulation and performance under pressure

Emotions and trait emotional intelligence among ultra-endurance runners

The effect of trait emotional intelligence on working memory across athletic expertise

The effect of athletic expertise and trait emotional intelligence on decision-making

The relationship between emotional intelligence and performance among college baseball players

Emotional intelligence in the national hockey league

Commentary: Emotional intelligence impact on half marathon finish times

Emotional plasticity: Conditions and effects of improving emotional competence in adulthood

Increasing emotional competence improves psychological and physical well-being, social relationships, and employability

Improving emotional intelligence: A systematic review of existing work and future challenges

How efficient are emotional intelligence trainings: A meta-analysis

Emotional intelligence training in team sports

Emotional intelligence (EI) training adapted to the international preparation constraints in rugby: Influence of EI trainer status on EI training effectiveness

Emotional competences training in equestrian sport-A preliminary study

Increasing emotional intelligence in cricketers: An intervention study

Using emotional intelligence in coaching high-performance athletes: A randomised controlled trial

Fundamentals of Physiology: A Human Perspective

The physiological effects of slow breathing in the healthy human

How breath-control can change your life: A systematic review on psycho-physiological correlates of slow breathing

Fourth Edition: A Practitioner's Guide

Hypothesis: Pulmonary afferent activity patterns during slow, deep breathing contribute to the neural induction of physiological relaxation

Breath of life: The respiratory vagal stimulation model of contemplative activity

How heart rate variability affects emotion regulation brain networks

Heart rate variability biofeedback: How and why does it work?

A practical guide to resonance frequency assessment for heart rate variability biofeedback

The Central Nervous System-Structure and Function

Heart rate variability as an index of regulated emotional responding

A model of neurovisceral integration in emotion regulation and dysregulation

Heart rate variability, prefrontal neural function, and cognitive performance: The neurovisceral integration perspective on self-regulation, adaptation, and health

The hierarchical basis of neurovisceral integration

The central autonomic network: Functional organization, dysfunction, and perspective

Heart rate variability: Origins, methods, and interpretive caveats

Standards of measurement, physiological interpretation, and clinical use. Task force of the european society of cardiology and the north american society of pacing and electrophysiology

Heart rate variability and cardiac vagal tone in psychophysiological research-Recommendations for experiment planning, data analysis, and data reporting

Time domain, geometrical and frequency domain analysis of cardiac vagal outflow: Effects of various respiratory patterns

A unifying conceptual framework of factors associated to cardiac vagal control

Enhancing cardiac vagal activity: Factors of interest for sport psychology. Prog

Influence of slow-paced breathing on inhibition after physical exertion

Influence of a 30-day slow paced breathing intervention compared to social media use on subjective sleep quality and cardiac vagal activity

The influence of slow-paced breathing on executive function

Influence of a single slow-paced breathing session on cardiac vagal activity in athletes

Keeping the pace: The effect of slow-paced breathing on error monitoring

The emerging field of emotion regulation: An integrative review

Emotion regulation: Affective, cognitive, and social consequences

Emotions in sport: Current issues and perspectives

The effects of COVID-19 pandemic on perceived stress and psychobiosocial states in Italian athletes

Associations of chronotype, Big Five, and emotional competences with perceived stress in university students

Work-related stress risk and preventive measures of mental disorders in the medical environment: An umbrella review

Inhalation/Exhalation ratio modulates the effect of slow breathing on heart rate variability and relaxation

Respiratory control as a treatment for panic attacks

Respiratory control: Its contribution to the treatment of panic attacks. A controlled study

Positive emotion reduces dyspnea during slow paced breathing

Mechanisms, assessment, and management: A consensus statement

Considerations in the assessment of heart rate variability in biobehavioral research

The effect of slow-paced breathing on stress management in adolescents with intellectual disability

Relative timing of inspiration and expiration affects respiratory sinus arrhythmia

Validity of occupational stress assessment using a visual analogue scale

Clinical stress assessment using a visual analogue scale

Measuring emotion: The self-assessment manikin and the semantic differential

Influence diagram of physiological and environmental factors affecting heart rate variability: An extended literature overview

The impact of emotions on the sensory and affective dimension of perceived dyspnea

Training of paced breathing at 0.1 Hz improves CO2 homeostasis and relaxation during a paced breathing task

Hypoventilation training for asthma: A case illustration

Monitoring training status with HR measures: Do all roads lead to Rome?

Heart rate variability biofeedback improves emotional and physical health and performance: A systematic review and meta analysis

Effect of heart rate variability biofeedback on sport performance, a systematic review

Can heart rate variability biofeedback improve athletic performance? A systematic review

Matter over mind: A randomised-controlled trial of singlesession biofeedback training on performance anxiety and heart rate variability in musicians

Commentary: Heart rate variability and self-control-A meta-analysis

Response: Commentary: Heart rate variability and self-control-A meta-analysis

Heart rate variability and self-control-A meta-analysis

Vagal tank theory: The three Rs of cardiac vagal control functioning-Resting, reactivity, and recovery

Using slow-paced breathing to foster endurance, well-being, and sleep quality in athletes during the COVID-19 pandemic

The tale of hearts and reason: The influence of mood on decision making

Is the ability to keep your mind sharp under pressure reflected in your heart? Evidence for the neurophysiological bases of decision reinvestment

The relationship between working memory, reinvestment, and heart rate variability

The contribution of coping related variables and cardiac vagal activity on the performance of a dart throwing task under pressure

The contribution of coping-related variables and cardiac vagal activity on prone rifle shooting performance under pressure

Coping related variables, cardiac vagal activity and working memory performance under pressure

Influence of transcutaneous vagus nerve stimulation on cardiac vagal activity: Not different from sham stimulation and no effect of stimulation intensity

Transcutaneous vagus nerve stimulation may enhance only specific aspects of the core executive functions. A randomized crossover trial

Transcutaneous vagus nerve stimulation via tragus or cymba conchae: Are its psychophysiological effects dependent on the stimulation area?

Performance habits: A framework proposal

Measurement and the interpretation of trait EI research

Trait emotional intelligence questionnaire full-form and short-form versions: Links with sport participation frequency and duration and type of sport practiced

Informed Consent Statement: Informed consent was obtained from all subjects involved in the study.Data Availability Statement: Data can be shared by the corresponding author upon reasonable request.

The authors declare no conflict of interest.