Heart rate variability stabilization in athletes: towards more convenient data acquisition

Agreement of ultra-short-term heart rate variability measure after different repeated bouts of sprint ability tests

This study aims to explore: (1) the validity of post-exercise ultra-short-term heart rate variability (HRVust) after two different bouts of repeated sprint ability test (RSA), and (2) the relationship between HRVust measure and RSA performance. Twenty adolescent male futsal players voluntarily participated in this study (age: 17.65 ± 1.81 years, body height: 170.88 ± 4.98 cm, body weight: 61.78 ± 4.67 kg). The participants performed a standard RSA test (RSAstandard) and an RSA test with a 10% decrement of the best sprint time test (RSA10%decrement) on two separate occasions within a week. On both occasions, a 5-min resting electrocardiography was administered pre- and post-RSA exercise protocols. The first 30-s (HRVust30s), 60-s (HRVust60s), and 60-120-s (HRVust1-2min) were extracted and used to compare with the standard of 5-min HRV recording (HRVcriterion). The natural logarithm (ln) of the standard deviation of normal-to-normal intervals (SDNN) and root mean square of successive normal-to-normal interval differences (RMSSD) HRV indices were utilised to establish intraclass correlation coefficient (ICC2,1), coefficient of variation (%CV), and Pearson product-moment correlation (r). Results revealed the ICC values of HRVust lnSDNN (RSAstandard = 0.77-0.88; RSA10%decrement = 0.41-0.71) and lnRMSSD (RSAstandard = 0.81-0.86; RSA10%decrement = 0.57-0.82). Furthermore, significantly positive correlations between best sprint time and post-exercise HRVust indices were found in lnSDNN (r = 0.47-0.62; p < 0.05) and lnRMSSD (r = 0.45; p < 0.05). Additionally, a large CV of lnSDNN (RSAstandard = 32%-45%; RSA10%decrement = 29%-39%), lnRMSSD (RSAstandard = 50%-66%; RSA10%decrement = 48%-52%), and ratio (RSAstandard = 45%-126%; RSA10%decrement = 27%-45%) was found after the RSA protocols. In conclusion, the number of bouts of RSA exercise potentially influences the agreement of post-exercise time-domain HRVust indices to standard HRV measure.

Autonomic nervous system and endocrine system response to upper or lower cervical spine mobilization in males with persistent post-concussion symptoms: a proof-of-concept trial

INTRODUCTION

The peripheral stress response, consisting of the autonomic nervous system (ANS) and hypothalamic pituitary adrenal-axis (HPA-axis), functions to maintain homeostasis in response to stressors. Cervical spine manual therapy has been shown to differentially modulate the stress response in healthy populations. No study has investigated whether cervical spine mobilizations can differentially modulate the stress response in individuals with persistent post-concussion symptoms (PPCS), a population characterized by a dysfunctional stress response.

METHODS

A randomized, controlled, parallel design trial was performed to investigate whether upper or lower cervical spine mobilization can differentially modulate components of the stress response in individuals with PPCS. The outcomes were salivary cortisol (sCOR) concentration (primary) and the HRV metric, rMSSD, measured with a smartphone application (secondary). Nineteen males diagnosed with PPCS, aged 19-35, were included. Participants were randomly assigned into either intervention group, upper (n = 10) or lower (n = 9) cervical spine mobilization. Each outcome was collected at different time points, pre- and post-intervention. Statistical analyses were performed using the Friedman's Two-Way ANOVA, Mann-Whitney U test, and Wilcoxon Signed Rank Test.

RESULTS

There was a statistically significant within-group reduction in sCOR concentration 30 minutes following lower cervical spine mobilizations and statistically significant within-group increase in rMSSD 30 minutes following upper cervical spine mobilizations.

CONCLUSION

The results of this trial provide preliminary evidence for cervical spine mobilizations to differentially modulate components of the stress response at specific time points. Understanding the mechanisms of the effect of cervical spine mobilizations on the stress response provides a novel rationale for selecting cervical spine mobilizations to rehabilitate individuals with PPCS.

Heart rate dynamics and asymmetry during sympathetic activity stimulation and post-stimulation recovery in ski mountaineers-a pilot exploratory study

There is a lack of studies on non-linear heart rate (HR) variability in athletes. We aimed to assess the usefulness of short-term HR dynamics and asymmetry parameters to evaluate the neural modulation of cardiac activity based on non-stationary RR interval series by studying their changes during sympathetic nervous system activity stimulation (isometric handgrip test) and post-stimulation recovery in professional ski mountaineers. The correlation between the changes in the parameters and the respiratory rate (RespRate) and also the duration of the career was analyzed. Short-term (5 min) and ultra-short-term (1 min) rates of patterns with no variations (0V), number of acceleration runs of length 1 (AR1), and short-term Porta's Index were greater, whereas Guzik's Index (GI) was smaller during sympathetic stimulation compared to rest. GI increased and the number of AR1 decreased during recovery. Greater increases in GI and RMSSD were associated with greater decreases in RespRate during recovery. Greater increases in RespRate from rest to short-term sympathetic stimulation were associated with greater increases in 0V (Max-min method) and AR1 but also with greater decreases in decelerations of short-term variance and accelerations and decelerations of long-term variance. Greater increases in 0V (Max-min method) and number of AR1 during sympathetic stimulation were associated with a shorter career duration. Greater decreases in these parameters during recovery were associated with a longer career duration. Changes in measures of HR dynamics and asymmetry, calculated based on short-term non-stationary RRi time series induced by sympathetic stimulation and post-stimulation recovery, reflected sympathovagal shift and were associated with condition-related alterations in RespRate and career duration in athletes who practice ski mountaineering.

Comparison of physiological outcomes after dynamic exertion between athletes at return to sport from concussion and controls: Preliminary findings

OBJECTIVES

Compare physiological (heart rate, heart rate variability, and blood pressure), performance (change-of-direction task completion time and errors), and clinical (symptoms and rating of perceived exertion) outcomes during dynamic exertion between athletes at return to sport after concussion to healthy athlete controls.

DESIGN

Case control.

METHODS

A sample of 23 (Female = 10; 43.5 %) athletes at medical clearance to play/activity from concussion (CONCUSS) and 23 sex-, age-, and sport-matched healthy athletes (CONTROLS) completed a 5-min seated rest before and after the dynamic exertion test. Independent sample t-tests were used to compare CONCUSS and CONTROLS for completion time, heart rate, and blood pressure; and Mann-Whitney U tests for symptoms, perceived exertion, and errors. A series of ANOVAs were conducted to compare heart rate variability between groups across pre- and post-exercise rest periods.

RESULTS

There were no differences in heart rate, blood pressure, symptoms, perceived exertion, and errors. CONCUSS were faster on Zig Zag (p = .048) and Pro Agility (p = .018) tasks, reported lower symptom severity (p = .019), and had lower post-EXiT HRV (p < .049) than CONTROLS.

CONCLUSIONS

Performance, symptoms, perceived exertion, and blood pressure outcomes from dynamic exertion were equivocal between athletes at medical clearance from concussion and healthy controls, which provide empirical support for dynamic exercise to inform medical clearance clinical decision making for sport-related concussion. However, differences in autonomic nervous system functioning indicate that additional research is needed to examine temporal changes in heart rate variability and other physiological outcomes following dynamic exertion.

Heart rate variability of elite female rowers in preparation for and during the national selection regattas: a pilot study on the relation to on water performance

Elite athletes require a delicate balance of physiological and psychological stress and recovery-essential for achieving optimal performance. Monitoring heart rate variability (HRV) provides a non-invasive estimation of both physiological and psychological stress levels, offering potentially valuable insights into health, performance, and adaptability. Previous studies, primarily conducted on male participants, have shown an association between HRV and performance in the context of rowing training. However, given the rigorous nature of rowing training, it is crucial to investigate HRV in elite rowers, particularly during the U.S. national selection regattas (NSR).

Purpose

To comprehensively analyze elite female rowers, evaluating acute changes in HRV and subjective psychometrics during the NSR.

Methods

Five elite female rowers (26 ± 2 years, 180 ± 8 cm, 82 ± 8 kg, 19 ± 6%fat) were recruited and tracked prior to and during NSR I and II. Morning HRV measures were completed using photoplethysmography (HRV4training) along with self-reported levels of fatigue, soreness, rating of perceived exertion, mentally energy and physical condition.

Results

Significant decreases were observed in log transformed root-mean square of successive differences (LnRMSSD; p = 0.0014) and fatigue (p = 0.01) from pre-to-during NSR, while mental energy (p = 0.01), physical condition (p = 0.01), and motivation (p = 0.006) significantly increased. These psychometric measures returned to pre-NSR levels, at post-NSR (all p < 0.05), though HRV remained slightly suppressed. NSR on-water performance was not correlated to LnRMSSD or the change in LnRMSSD (p > 0.05).

Discussion

HRV and psychometric measures are sensitive to the stress of elite rowing competition in females. However, HRV was not associated with on-water rowing performance during an elite rowing competition.

Individually guided training prescription by heart rate variability and self-reported measure of stress tolerance in recreational runners: Effects on endurance performance

The aim of this study was to determine the effect of endurance training individually guided by objective (Heart Rate Variability-HRV) or self-report measure of stress (DALDA-questionnaire) in comparison to predefined endurance training prescription for improving endurance performance in recreational runners. After a 2-week preliminary baseline period to establish resting HRV and self-reported measure of stress, thirty-six male recreational runners were randomly assigned to HRV-guided (G_HRV; n = 12), DALDA-guided (G_D; n = 12) or predefined training (G_T; n = 12) prescription groups. Before and after 5-weeks of endurance training, participants performed a track field peak velocity (V_{peak_TF}), time limit (T_lim) at 100% of V_{peak_TF} and 5 km time-trial (5 km TT) tests. G_D lead to higher improvements in V_{peak_TF} (8.4 ± 1.8%; ES = 1.41) and 5 km TT (-12.8 ± 4.2%; ES = -1.97), than G_HRV (6.6 ± 1.5% and -8.3 ± 2.8%; ES = -1.20; 1.24) and G_T (4.9 ± 1.5% and -6.0 ± 3.3%; ES = -0.82; 0.68), respectively, with no differences for T_lim. Self-report measures of stress may be used to individualize endurance training prescription on a daily basis leading to better performance enhancement, which may be used with HRV for a holistic understanding of daily training-induce adaptations.

Designing an App to Promote Physical Exercise in Sedentary People Using a Day-to-Day Algorithm to Ensure a Healthy Self-Programmed Exercise Training

Heart rate variability (HRV) has allowed the implementation of a methodology for daily decision making called day-to-day training, which allows data to be recorded by anyone with a smartphone. The purpose of the present work was to evaluate the validity and reliability of HRV measurements with a new mobile app (Selftraining UMH) in two resting conditions. Twenty healthy people (10 male and 10 female) were measured at rest in supine and seated positions with an electrocardiogram and an application for smartphones at the same time (Selftraining UMH) using recordings obtained through an already validated chest-worn heart rate monitor (Polar H10). The Selftraining UMH app showed no significant differences compared to an electrocardiogram, neither in supine nor in sitting position (p > 0.05) and they presented almost perfect correlation levels (r ≥ 0.99). Furthermore, no significant differences were found between ultra-short (1-min) and short (5-min) length measurements. The intraclass correlation coefficient showed excellent reliability (>0.90) and the standard error of measurement remained below 5%. The Selftraining UMH smartphone app connected via Bluetooth to the Polar H10 chest strap can be used to register daily HRV recordings in healthy sedentary people.

Acute Effects of a Single-Session of Full-Body Foam Rolling on Heart Rate Variability

Background

Self-myofascial release has been demonstrated to increase relaxation and improve blood flow, yet it is unknown if it can elicit an acute effect on heart rate variability (HRV).

Purpose

This study aimed to determine if a single-bout of foam rolling could increase parasympathetic activity as measured by HRV.

Methods

Twenty (20) participants volunteered and their baseline HRV was assessed using a finger sensor while lying supine, and then a second measure was recorded with them sitting upright with feet on the ground. This study utilized a practical HRV collection method designed for use in the field settings, and the data is recorded in arbitrary units (A.U.). Participants then oscillated on a closed-cell cylindrical foam roller using their body weight on the triceps surae, hamstrings, quadriceps, lumbar spine, and pectoral muscles each for 60 sec. Participants first massaged the right limb and then repeated on the matching muscle group on the left before continuing to the next region. Follow-up HRV measurements were recorded using the same procedures.

Results

Paired samples t tests assessing pre- and post-foam–rolling HRV measures in supine and seated positions revealed no difference between supine measures (p = .05, d = 0.21), nor the seated measures (p = .27, d = 0.17) among all participants. When sexes were analyzed separately, males showed a significant decrease in HRV in supine positions (p = .03, d = 0.33), but females did not (p = .55, d = 0.09).

Conclusions

The single bout of foam rolling on large muscle groups did not increase parasympathetic activity as hypothesized. Males and females responded differently in supine positions, but no difference was present in seated positions across sexes. The task of self-massage may have prevented the anticipated response from the massage. Further research should investigate if passive massage is more effective on HRV response.

Self-recorded heart rate variability profiles are associated with health and lifestyle markers in young adults

PURPOSE

To quantify associations between self-recorded heart rate variability (HRV) profiles and various health and lifestyle markers in young adults.

METHODS

Otherwise healthy volunteers (n = 40, 50% male) recorded 60-s, post-waking HRV with a cost-free mobile application in supine and standing positions for 7 days. The 7-day average and coefficient of variation (CV, reflects daily fluctuation) for the mean RR interval and root mean square of successive differences (LnRMSSD) were assessed. 7-day sleep duration and physical activity profiles were characterized via wrist-worn accelerometer. Subsequent laboratory assessments included aerobic fitness ([Formula: see text]O₂peak) and markers of cardiovascular, metabolic, and psychoemotional health. Associations were evaluated before and after [Formula: see text]O₂peak adjustment.

RESULTS

Bivariate correlations (P < 0.05) demonstrated that higher 7-day averages and/or lower CV values were associated with higher activity levels and superior cardiovascular (lower systolic and diastolic blood pressure [BP] and aortic stiffness [cf-PWV]), metabolic (lower body fat percentage, fasting glucose, and low-density lipoprotein cholesterol [LDL-C]), and psychoemotional health (lower perceived stress) markers, with some variation between sexes and recording position. In males, associations between HRV parameters and cf-PWV remained significant following [Formula: see text]O₂peak adjustment (P < 0.05). In females, HRV parameters were associated (P < 0.05) with numerous cardiovascular (systolic and diastolic BP, cf-PWV) and metabolic (fasting glucose and LDL-C) parameters following [Formula: see text]O₂peak adjustment.

CONCLUSIONS

Higher or more stable supine and standing HRV were generally associated with superior health and lifestyle markers in males and females. These findings lay groundwork for future investigation into the usefulness of self-recorded ultra-short HRV as a health-promoting behavior-modification tool in young adults.

Validity and reliability of different smartphones applications to measure HRV during short and ultra-short measurements in elite athletes

BACKGROUND AND OBJECTIVE

Heart rate variability (HRV) has been proposed as a useful marker that can show the performance adaptation and optimize the training process in elite athletes. The development of wearable technology permits the measurement of this marker through smartphone applications. The purpose of this study is to assess the validity and reliability of short and ultra-short HRV measurements in elite cyclists using different smartphone applications.

METHOD

Twenty-six professional cyclists were measured at rest in supine and in seated positions through the simultaneous use of an electrocardiogram and two different smartphone applications that implement different technologies to measure HRV: Elite HRV (with a chest strap) and Welltory (photoplethysmography). Level of significance was set at p < 0.05.

RESULTS

Compared to an electrocardiogram, Elite HRV and Welltory showed no differences neither in supine nor in seated positions (p > 0.05) and they showed very strong to almost perfect correlation levels (r = 0.77 to 0.94). Furthermore, no differences were found between short (5 min) and ultra-short (1 min) length measurements. Intraclass correlation coefficient showed good to excellent reliability and the standard error of measurement remained lower than 6%.

CONCLUSION

Both smartphone applications can be implemented to monitor HRV using short- and ultra-short length measurements in elite endurance athletes.

Validation of a smart shirt for heart rate variability measurements at rest and during exercise

Heart rate variability (HRV) monitoring is a promising option to estimate the autonomic nervous system regulation responding to exercise. Textiles with embedded sensors recording heartbeat intervals are a simple tool for data collection. So-called smart shirts offer comfort for a daily use and are managed easily. Their measurement accuracy for HRV calculation at rest is promising but remains questionable during exercise. Therefore, the present study validated the Ambiotex smart shirt using HRV indices (RMSSD, rel. HF power and rel. LF power) during exercise. Eighty-three healthy participants (31 ± 6 years; 39 females, 44 males) completed an incremental exercise test on a bicycle ergometer wearing the smart shirt and an electrocardiogram simultaneously. We compared HRV indices of segments at rest (5 min), at warm-up (3 min) and twice at the exercise test (each 5 min). At rest and at warm-up, we observed excellent linear relationship (r > 0.96; R² > 0.94), excellent relative reliability (ICC ≥ 0.98; α ≥ 0.98) and acceptable agreement (bias < 10%). During the exercise test, measurement accuracy declined with increasing intensity but remained high (> 0.8), although results for partial HRV indices were insufficient. In addition, percentage bias was unacceptable during exercise test. However, the findings support the validity of the smart shirt for measuring HRV especially at rest and at warm-up. We suggest using the smart shirt for monitoring HRV indices on a daily basis but caution should be taken in the interpretation of HRV indices obtained during moderate to vigorous exercise intensities. This article is protected by copyright. All rights reserved.

Reliability of Symbolic Analysis of Heart Rate Variability and Its Changes During Sympathetic Stimulation in Elite Modern Pentathlon Athletes: A Pilot Study

Background and Purpose

Most studies on heart rate variability (HRV) in professional athletes concerned linear, time-, and frequency-domain indices, and there is lack of studies on non-linear parameters in this group. The study aimed to determine the inter-day reliability, and group-related and individual changes of short-term symbolic dynamics (SymDyn) measures during sympathetic nervous system activity (SNSa) stimulation among elite modern pentathletes.

Methods

Short-term electrocardiographic recordings were performed in stable measurement conditions with a 7-day interval between tests. SNSa stimulation via isometric handgrip strength test was conducted on the second day of study. The occurrence rate of patterns without variations (0V), with one variation (1V), two like (2LV), and two unlike variations (2UV) obtained using three approaches (the Max–min, the σ, and the Equal-probability methods) were analyzed. Relative and absolute reliability were evaluated.

Results

All SymDyn indices obtained using the Max–min method, 0V, and 2UV obtained using the σ method, 2UV obtained using the Equal-probability method presented acceptable inter-day reliability (the intraclass correlation coefficient between .91 and .99, Cohen’s d between −.08 and .10, the within-subject coefficient of variation between 4% and 22%). 2LV, 2UV, and 0V obtained using the Max–min and σ methods significantly decreased and increased, respectively, during SNSa stimulation—such changes were noted for all athletes. There was no significant association between differences in SymDyn parameters and respiratory rate in stable conditions and while comparing stable conditions and SNSa stimulation.

Conclusion

SymDyn indices may be used as reliable non-respiratory-associated parameters in laboratory settings to detect autonomic nervous system (ANS) activity modulations in elite endurance athletes. These findings provide a potential solution for addressing the confounding influence of respiration frequency on HRV-derived inferences of cardiac autonomic function. For this reason, SymDyn may prove to be preferable for field-based monitoring where measurements are unsupervised.

What Is behind Changes in Resting Heart Rate and Heart Rate Variability? A Large-Scale Analysis of Longitudinal Measurements Acquired in Free-Living

The aim of this study was to investigate the relationship between heart rate and heart rate variability (HRV) with respect to individual characteristics and acute stressors. In particular, the relationship between heart rate, HRV, age, sex, body mass index (BMI), and physical activity level was analyzed cross-sectionally in a large sample of 28,175 individuals. Additionally, the change in heart rate and HRV in response to common acute stressors such as training of different intensities, alcohol intake, the menstrual cycle, and sickness was analyzed longitudinally. Acute stressors were analyzed over a period of 5 years for a total of 9 million measurements (320±374 measurements per person). HRV at the population level reduced with age (p < 0.05, r = -0.35, effect size = moderate) and was weakly associated with physical activity level (p < 0.05, r = 0.21, effect size = small) and not associated with sex (p = 0.35, d = 0.02, effect size = negligible). Heart rate was moderately associated with physical activity level (p < 0.05, r = 0.30, effect size = moderate) and sex (p < 0.05, d = 0.63, effect size = moderate) but not with age (p = 0.35, r = -0.01). Similar relationships between BMI, resting heart rate (p < 0.05, r = 0.19, effect size = small), and HRV (p < 0.05, r = -0.10, effect size = small) are shown. In response to acute stressors, we report a 4.6% change in HRV (p < 0.05, d = 0.36, effect size = small) and a 1.3% change in heart rate (p < 0.05, d = 0.38, effect size = small) in response to training, a 6% increase in heart rate (p < 0.05, d = 0.97, effect size = large) and a 12% reduction in HRV (p < 0.05, d = 0.55, effect size = moderate) after high alcohol intake, a 1.6% change in heart rate (p < 0.05, d = 1.41, effect size = large) and a 3.2% change in HRV (p < 0.05, d = 0.80, effect size = large) between the follicular and luteal phases of the menstrual cycle, and a 6% increase in heart rate (p < 0.05, d = 0.97, effect size = large) and 10% reduction in HRV (p < 0.05, d = 0.47, effect size = moderate) during sickness. Acute stressors analysis revealed how HRV is a more sensitive but not specific marker of stress. In conclusion, a short resting heart rate and HRV measurement upon waking using a smartphone app can effectively be used in free-living to quantify individual stress responses across a large range of individuals and stressors.

Optimizing Intersession Reliability of Heart Rate Variability-The Effects of Artifact Correction and Breathing Type

Gisselman, AS, D'Amico, M, and Smoliga, JM. Optimizing intersession reliability of heart rate variability-the effects of artifact correction and breathing type. J Strength Cond Res 34(11): 3199-3207, 2020-This study aimed to comprehensively investigate the reliability of multiple heart rate variability (HRV) parameters and to explore the influence of artifact removal and breathing condition on HRV reliability. Resting HRV was collected using Polar Team monitors on 41 participants (age: 19.9 ± 1.2 years; 28 females and 13 males) during 2 separate days. Within each session, participants performed 10 minutes each of spontaneous and controlled breathing (randomized order). Kubios HRV analysis software was used to analyze 180-second data epochs using "low" or "strong" artifact removal. Relative reliability was assessed using intraclass correlation coefficient (ICC2,1), and absolute reliability was quantified using mean-normalized SEM%. Time-domain and nonlinear parameters produced poor to good intersession agreement (ICC = 0.34-0.68; SEM% = 11.0-39.0) with "low" artifact removal, regardless of breathing condition. Frequency-domain parameters demonstrated fair intersession agreement during controlled breathing (ICC = 0.40-0.45; SEM% = 26.0-70.0) but poor agreement during spontaneous breathing (ICC = 0.07-0.13; SEM% = 32.0-81.0). Minimal differences in ICCs were observed between "low" and "strong" artifact removal. Thus, this study provides 3 practical applications: (a) HRV monitoring is most reliable when using time-domain and nonlinear parameters, regardless of breathing or filtering condition, but no single parameter is especially reliable. The large variation and poor intersession reliability of frequency indices during spontaneous breathing are improved by controlling breathing rate; (b) "Low" artifact removal seems superior to more aggressive artifact removal; and (c) intersession differences in HRV measurements <30% may be indicative of normal daily variation rather than true physiologic changes.

Assessing the Accuracy of Popular Commercial Technologies That Measure Resting Heart Rate and Heart Rate Variability

Commercial off-the shelf (COTS) wearable devices continue development at unprecedented rates. An unfortunate consequence of their rapid commercialization is the lack of independent, third-party accuracy verification for reported physiological metrics of interest, such as heart rate (HR) and heart rate variability (HRV). To address these shortcomings, the present study examined the accuracy of seven COTS devices in assessing resting-state HR and root mean square of successive differences (rMSSD). Five healthy young adults generated 148 total trials, each of which compared COTS devices against a validation standard, multi-lead electrocardiogram (mECG). All devices accurately reported mean HR, according to absolute percent error summary statistics, although the highest mean absolute percent error (MAPE) was observed for CameraHRV (17.26%). The next highest MAPE for HR was nearly 15% less (HRV4Training, 2.34%). When measuring rMSSD, MAPE was again the highest for CameraHRV [112.36%, concordance correlation coefficient (CCC): 0.04], while the lowest MAPEs observed were from HRV4Training (4.10%; CCC: 0.98) and OURA (6.84%; CCC: 0.91). Our findings support extant literature that exposes varying degrees of veracity among COTS devices. To thoroughly address questionable claims from manufacturers, elucidate the accuracy of data parameters, and maximize the real-world applicative value of emerging devices, future research must continually evaluate COTS devices.

Ultrashort Versus Criterion Heart Rate Variability Among International-Level Girls' Field Hockey Players

PURPOSE

To assess heart rate (HR) variability responses to various markers of training load, quantify associations between HR variability and fitness, and compare responses and associations between 1-minute ultrashort and 5-minute criterion measures among a girls' field hockey team.

METHODS

A total of 11 players (16.8 [1.1] y) recorded the logarithm of the root mean square of successive differences (LnRMSSD) daily throughout a 4-week training camp. The weekly mean (LnRMSSDM) and coefficient of variation (LnRMSSDCV) were analyzed. The internal training load (ITL) and external training load (ETL) were acquired with session HR and accelerometry, respectively. Speed, agility, repeated sprint ability, and intermittent fitness were assessed precamp and postcamp.

RESULTS

Similar increases in the ultrashort and criterion LnRMSSDM were observed in week 3 versus week 1 (P < .05-.06, effect size [ES] = 0.28 to 0.36). The ultrashort and criterion LnRMSSDCV showed small ES reductions in week 2 (ES = -0.40 to -0.50), moderate reductions in week 3 (ES = -0.61 to -0.72), and small reductions in week 4 (ES = -0.42 to -0.51) versus week 1 (P > .05). Strong agreement was observed between the ultrashort and criterion values (intraclass correlation coefficient = .979). The ITL:ETL ratio peaked in week 1 (P < .05 vs weeks 2-4), displaying a weekly pattern similar to LnRMSSDCV, and inversely similar to LnRMSSDM. Changes in the ultrashort and criterion LnRMSSDCV from week 1 to 4 were associated with ITL (P < .01). The ultrashort and criterion LnRMSSDCV in week 4 were associated (P < .05) with postcamp fitness.

CONCLUSIONS

The ultrashort HR variability parameters paralleled the criterion responses, and the associations with ITL and fitness were similar in magnitude.

Agreement of Ultra-Short-Term Heart Rate Variability Recordings During Overseas Training Camps in Under-20 National Futsal Players

Background: Monitoring the daily change in resting heart rate variability (HRV) can provide information regarding training adaptation and recovery status of the autonomic nervous system (ANS) during training camps. However, it remains unclear whether postural stabilization is essential for valid and reliable ultra-short-term (HRV_UST) recordings in short-term overseas training camps.

Design: Observational and longitudinal study.

Purpose: This study aimed to investigate ultra-short-term heart rate variability recordings under stabilization or post-stabilization periods in four overseas training camps.

Participant: Twenty-seven U-20 male national team futsal players voluntarily participated in this study.

Method: Resting HRV was evaluated for 10 min during the early morning of each training camp. The natural logarithm of the root mean square of successive normal-to-normal interval differences (LnRMSSD) was used for comparisons. Time segments of HRV were divided into two periods with three measures within each: (1) the first 30-s (1st_30 s LnRMSSD), the first 60-s (1st_60 s LnRMSSD), and the 5-min standard (1st_5 min LnRMSSD) during stabilization; (2) the first 30-s (2nd_30 s LnRMSSD), the first 60-s (2nd_60 s LnRMSSD), and the 5-min standard (2nd_5 min LnRMSSD) after stabilization.

Result: The results demonstrated trivial to small ES (−0.03; 0.46), very large to nearly perfect ICC (0.76; 0.98), and narrow range of SEM (0.06; 0.31) when all time segments of HRV_UST were compared to the 1st_5 min and 2nd_5 min HRV. Furthermore, the magnitude of the correlation coefficients ranged from very high to nearly perfect for all the time segments (r = 0.83; 0.97). The HRV_UST posted excellent agreement in all time segments (bias = −0.05; 0.12) with/without postural stabilization. Trivial to small levels of effect size in all time segments of LnRMSSD_mean (0.02; 0.41 ES) and LnRMSSD_cv (−0.49; −0.02 ES) across overseas training camps was identified.

Conclusion: The first 30 or 60-s LnRMSSD recordings can be used to evaluate daily cardiac-autonomic function during overseas training camps in futsal players. The process for stabilization seems to be unnecessary for measuring the morning resting LnRMSSD in overseas training camps among young adult futsal players.

Heart-Rate Variability Recording Time and Performance in Collegiate Female Rowers

PURPOSE

To assess the agreement of the root mean square of successive R-R interval (RMSSD) values when recorded immediately upon waking to values recorded later in the morning prior to practice, and to determine the associations of the RMSSD recordings with performance outcomes in female rowers.

METHODS

A total of 31 National Collegiate Athletic Association Division I rowers were monitored for 6 consecutive days. Two seated RMSSD measurements were obtained on at least 3 mornings using a smartphone-based photoplethysmography application. Each 1-minute RMSSD measure was recorded following a 1-minute stabilization period. The first (T1) measurement occurred at the athlete's home following waking, while the second (T2) transpired upon arrival at the team's boathouse immediately before practice. From the measures, the RMSSD mean and coefficient of variation were calculated. Two objective performance assessments were conducted on an indoor rowing ergometer on separate days: 2000-m time trial and distance covered in 30 minutes. Interteam rank was determined by the coaches, based on subjective and objective performance markers.

RESULTS

The RMSSD mean (intraclass correlation coefficient = .82; 95% CI, .63 to .92) and RMSSD coefficient of variation (intraclass correlation coefficient = .75; 95% CI, .48 to .88) were strongly correlated at T1 and T2, P < .001. The RMSSD mean at T1 and T2 was moderately associated with athlete rank (r = -.55 and r = -.46, respectively), 30-minute distance (r = .40 and r = .41, respectively), and 2000 m at T1 (r = -.37), P < .05. No significant correlations were observed for the RMSSD coefficient of variation.

CONCLUSION

Ultrashort RMSSD measurements taken immediately upon waking show very strong agreement with those taken later in the morning, at the practice facility. Future research should more thoroughly investigate the relationship between specific performance indices and the RMSSD mean and coefficient of variation for female collegiate rowers.

Wearable Devices Suitable for Monitoring Twenty Four Hour Heart Rate Variability in Military Populations

Heart rate variability (HRV) measurements provide information on the autonomic nervous system and the balance between parasympathetic and sympathetic activity. A high HRV can be advantageous, reflecting the ability of the autonomic nervous system to adapt, whereas a low HRV can be indicative of fatigue, overtraining or health issues. There has been a surge in wearable devices that claim to measure HRV. Some of these include spot measurements, whilst others only record during periods of rest and/or sleep. Few are capable of continuously measuring HRV (≥24 h). We undertook a narrative review of the literature with the aim to determine which currently available wearable devices are capable of measuring continuous, precise HRV measures. The review also aims to evaluate which devices would be suitable in a field setting specific to military populations. The Polar H10 appears to be the most accurate wearable device when compared to criterion measures and even appears to supersede traditional methods during exercise. However, currently, the H10 must be paired with a watch to enable the raw data to be extracted for HRV analysis if users need to avoid using an app (for security or data ownership reasons) which incurs additional cost.

PHYSICAL TRAINING IN ATHLETES: ANALYSIS OF CARDIAC AUTONOMIC MODULATION

ABSTRACT Introduction Cardiac autonomic modulation (CAM) is a result of the balance between the sympathetic and parasympathetic systems. This interaction results in heart rate variation (HRV), analyzed by specific electrocardiographic parameters. These parameters are modified by the practice of physical activity, indicating better cardiac conditioning. Objectives To evaluate the cardiac autonomic modulation of athletes of the XXVIII Ecological Walk at two separate times during their period of physical training. Also, to link the practice of physical activity with stress reduction in these individuals. Methods 24-hour Holter exams were performed at two times (before and after a 2-month period of non-standard physical training), and the results were analyzed using the software programs Epi-Info 7 and BioEstat 5.0. Inferential analysis was performed by the nonparametric Shapiro-Wilk test. Statistical significance was assigned to p values less than 0.05, with 95% confidence interval (95% CI). Results The sample was mostly male (n = 14; 77.78%), with a mean age of 49.55 years. No individual trained for less than 60 days; most (47.06%) trained for 151-200 days, with walking being the predominant modality (64.71%). No statistically significant difference was found in the parameters HRV pNN50 (p = 0.18), rMSSD (p = 0.14) or HF (p = 0.117) after the evaluated training period. Conclusions Participants who are longtime sportsmen and physically active showed parasympathetic saturation, therefore, they did not show significant changes in HRV. Also, low levels of stress were observed in those who practiced physical activity. Level of evidence II; Prognosis Study.

Changes in Short-Term and Ultra-Short Term Heart Rate, Respiratory Rate, and Time-Domain Heart Rate Variability Parameters during Sympathetic Nervous System Activity Stimulation in Elite Modern Pentathlonists-A Pilot Study

Monitoring of markers reflecting cardiac autonomic activity before and during stressful situations may be useful for identifying the physiological state of an athlete and may have medical or performance implications. The study aimed to determine group and individual changes in short-term (5 min) and ultra-short-term (1 min) heart rate (HR), respiratory rate (RespRate), and time-domain heart rate variability (HRV) parameters during sympathetic nervous system activity (SNSa) stimulation among professional endurance athletes. Electrocardiographic recordings were performed in stable measurement conditions (Baseline) and during SNSa stimulation via isometric handgrip in 12 elite modern pentathlonists. Significant increases in short-term HR and decreases in time-domain HRV parameters with no changes in RespRate were observed during SNSa stimulation. Significant differences were observed between Baseline (all minutes) and the last (i.e., 5th) minute of SNSa stimulation for ultra-short-term parameters. Analysis of intra-individual changes revealed some heterogeneity in responses. The study provides baseline responses of HR, RespRate, and time-domain HRV parameters to SNSa stimulation among elite pentathlonists, which may be useful for identifying abnormal responses among fatigued or injured (e.g., concussed) athletes. More attention to individual analysis seems to be necessary when assessing physiological responses to sympathetic stimuli in professional endurance athletes.

Weekly vagal modulations and their associations with physical fitness and physical activity

The root mean square of successive differences (RMSSD) of R-R intervals, the most robust vagal modulation parameter of heart rate variability (HRV), has been proposed as a marker of global health and training adaptations. The weekly averaging of RMSSD and its natural logarithm (LnRMSSD) has been adopted to enhance detection of training-induced adaptations. We assessed measures of aerobic fitness, body composition, objective physical activity (PA), and daily LnRMSSD recordings during different conditions, such as supine rest, seated rest, standing and walking at 5 km/h, over a week in 34 healthy young individuals of both sexes (age: 22 ± 4 yr; body fatness: 20 ± 8%; estimated VO₂max: 40 ± 8 mL·kg^-1·min^-1). The day-to-day reliability and agreement among LnRMSSD averages over 5, 4, 3, 2 and a single-day value per condition were assessed, while correlations between LnRMSSD, aerobic fitness, body composition, and PA were also examined. Poor to good day-to-day reliability, and moderate to excellent agreement were observed for LnRMSSD recordings for diverse conditions with a minimum of two daily recordings in the supine condition, and three in the other conditions achieving excellent agreement for weekly HRV assessment. Several correlations between LnRMSSD, aerobic fitness, body composition, and PA were revealed, with stronger observed associations during walking. Utilisation of weekly HRV (average of 2-3 daily recordings), as described in the current study, may provide practitioners with a tool to assess weekly vagal modulations for health and performance purposes. Walking HRV recordings may be a practical alternative to other conditions for the investigation of cardiac autonomic function.

Selected Cardiovascular and Psychological Changes Throughout a Competitive Season in Collegiate Female Swimmers

Dobson, J, Harris, B, Claytor, A, Stroud, L, Berg, L, and Chrysosferidis, P. Selected cardiovascular and psychological changes throughout a competitive season in collegiate female swimmers. J Strength Cond Res 34(11): 3062-3069, 2020-Measures that reflect the balance between training-induced fatigue and recovery can provide valuable feedback to help revise training plans. The aim of this study was to use multidimensional measures of the vagal control of the heart rate (HR), psychological stress, and burnout to investigate the impact of overload training and tapering in female swimmers. Thirteen female Division-1 swimmers completed the HR and psychological measures 3 times during a competitive season: (a) at the beginning of the season (BL), (b) eleven weeks later during a period of overload training (OL), and (c) eleven more weeks later and after a taper (TP). Cardiovascular measures included the resting logarithm of the root mean square of successive R-R intervals (lnRMSSD), HR responses to forced breathing (HRdiff), and HR responses to sustained handgrip exercise (HRhg). Psychological measures consisted of the Athlete Burnout Questionnaire and the Recovery-Stress Questionnaire. Repeated measures analyses of variance revealed that sport devaluation, reduced accomplishment, general stress, and emotional exhaustion all increased throughout the season (all were p < 0.05). Also, lnRMSSDrest decreased (p < 0.01) and HRhg increased (p < 0.05) during OL, both of which then returned to BL levels during TP (p < 0.05 and p < 0.01, respectively); whereas HRdiff values fell progressively during the season (p < 0.05). The results indicate that OL impaired cardiac vagal stimulation, and the bulk of evidence indicated that it was fully restored during a TP. In conclusion, lnRMSSD and HRhg were particularly sensitive to changes in workload throughout the season, and so those measures may be especially useful for preventing an excessive accumulation of training-induced fatigue.

Suitability of Ultra-Short-Term Heart Rate Variability in Military Trainees

We aimed to (a) evaluate the agreement between ultra-short-term and criterion resting heart rate variability (HRV) measures in military trainees, and (b) compare associations between HRV recording lengths and body composition. HRV recordings were performed for 10 min in 27 military male students. Mean RR interval, the root-mean square of successive differences (RMSSD), RMSSD:RR interval ratio, standard deviation of normal-to-normal RR intervals (SDNN), and SDNN:RR interval ratio were determined from the last 5 min of the 10-min recording and considered the criterion. Parameters were also recorded in successive 1-min epochs from the 5-min stabilization period. No differences were observed between criterion values and any of the 1-min epochs (p > 0.05). Effect sizes ranged from -0.36-0.35. Intra-class correlations ranged from 0.83-0.99. Limits of agreement ranged from 38.3-78.4 ms for RR interval, 18.8-30.0 ms for RMSSD, 1.9-3.1 for RMSSD:RR, 24.1-31.4 ms for SDNN, and 2.5-3.0 for SDNN:RR. Body fat% was associated (p < 0.05) with all HRV parameters at varying time segments. A 1-min HRV recording preceded by a 1-min stabilization period seems to be a suitable alternative to criterion measures. Ultra-short procedures may facilitate routine HRV tracking in tactical populations for status-monitoring purposes.

A Pilot Study of the Reliability and Agreement of Heart Rate, Respiratory Rate and Short-Term Heart Rate Variability in Elite Modern Pentathlon Athletes

Research on reliability of heart rate variability (HRV) parameters in athletes has received increasing attention. The aims of this study were to examine the inter-day reliability of short-term (5 min) and ultra-short-term (1 min) heart rate (HR), respiratory rate (RespRate) and HRV parameters, agreement between short-term and ultra-short-term parameters, and association between differences in HR, RespRate and HRV parameters in elite modern pentathletes. Electrocardiographic recordings were performed in stable measurement conditions with a week interval between tests. Relative reliability was evaluated by intra-class correlation coefficients, absolute reliability was evaluated by within-subject coefficient of variation, and agreement was evaluated using Bland-Altman (BA) plot with limits of agreement and defined a priori maximum acceptable difference. Short-term HR, RespRate, log transformed (ln) root mean square of successive normal-to-normal interval differences (lnRMSSD), ln high frequency (lnHF) and SD2/SD1 HRV indices and ultra-short-term HR, RespRate and lnRMSSD presented acceptable, satisfactory inter-day reliability. Although there were no significant differences between short-term and ultra-short-term HR, RespRate and lnRMSSD, no parameter showed acceptable differences with BA plots. Differences in time-domain and non-linear HRV parameters were more correlated with differences in HR than with differences in RespRate. Inverse results were observed for frequency-domain parameters. Short-term HR, RespRate, lnRMSSD, lnHF, and SD2/SD1 and ultra-short-term HR, RespRate and lnRMSSD could be used as reliable parameters in endurance athletes. However, practitioners should interpret changes in HRV parameters with regard to concomitant differences in HR and RespRate and caution should be taken before considering 5 min and 1 min parameters as interchangeable.

Validity of Smartphone Heart Rate Variability Pre- and Post-Resistance Exercise

The aim was to examine the validity of heart rate variability (HRV) measurements from photoplethysmography (PPG) via a smartphone application pre- and post-resistance exercise (RE) and to examine the intraday and interday reliability of the smartphone PPG method. Thirty-one adults underwent two simultaneous ultrashort-term electrocardiograph (ECG) and PPG measurements followed by 1-repetition maximum testing for back squats, bench presses, and bent-over rows. The participants then performed RE, where simultaneous ultrashort-term ECG and PPG measurements were taken: two pre- and one post-exercise. The natural logarithm of the root mean square of successive normal-to-normal (R-R) differences (LnRMSSD) values were compared with paired-sample t-tests, Pearson product correlations, Cohen’s d effect sizes (ESs), and Bland–Altman analysis. Intra-class correlations (ICC) were determined between PPG LnRMSSDs. Significant, small–moderate differences were found for all measurements between ECG and PPG: Base_Pre1 (ES = 0.42), Base_Pre2 (0.30), RE_Pre1 (0.26), RE_Pre2 (0.36), and RE_Post (1.14). The correlations ranged from moderate to very large: Base_Pre1 (r = 0.59), Base_Pre2 (r = 0.63), RE_Pre1 (r = 0.63), RE_Pre2 (r = 0.76), and RE_Post (r = 0.41)—all p < 0.05. The agreement for all the measurements was “moderate” (0.10–0.16). The PPG LnRMSSD exhibited “nearly-perfect” intraday reliability (ICC = 0.91) and “very large” interday reliability (0.88). The smartphone PPG was comparable to the ECG for measuring HRV at rest, but with larger error after resistance exercise.

Alterations in Cardiac Vagal Modulation-to-Vagal Tone Ratio in response to accumulated exercise stress in intermittent team sport

Study aim: This investigation examined the cardiac vagal modulation-to-vagal tone ratio and its utility to represent the dose response to accumulated exercise stress in intermittent team sport.

Material and methods: Fourteen international calibre female field hockey players training as part of a national team were participants over a three-week period. Exercise stress was expressed through cardiovascular strain using heart rate (HR) dynamics and was quantified as a training load (AU) and time spent exercising above anaerobic threshold (min). Cardiac autonomic activity was examined using heart rate variability; R-R intervals (ms) were collected immediately upon awakening throughout each weekend. The square root of the mean squared differences of successive R–R intervals were individually calculated, and log transformed prior to being averaged (Ln rMSSD) along with the corresponding mean R-R interval length. Multiple linear regression analysis examined the association between cardiac autonomic activity and indices of accumulated exercise stress.

Results: Significant inverse associations (95% CI) between the Ln rMSSD:R-R ratio and both training load [r = –0.48 (–0.70: –0.18), p = 0.012] and time spent exercising above anaerobic threshold [r = –0.51 (–0.72 : –0.22), p = 0.006] were observed. The association between mean R-R interval length and Ln rMSSD was not significant [r = 0.05, p = 0.950].

Conclusion: The current study demonstrated high intensity exercise, as defined through time spent above anaerobic threshold, displayed a stronger association with the Ln rMSSD:R-R ratio compared to a HR-derived training load when examining the dose response to accumulated intermittent exercise.

A Novel Smartphone App for the Measurement of Ultra-Short-Term and Short-Term Heart Rate Variability: Validity and Reliability Study

Background

Smartphone apps for heart rate variability (HRV) measurement have been extensively developed in the last decade. However, ultra–short-term HRV recordings taken by wearable devices have not been examined.

Objective

The aims of this study were the following: (1) to compare the validity and reliability of ultra–short-term and short-term HRV time-domain and frequency-domain variables in a novel smartphone app, Pulse Express Pro (PEP), and (2) to determine the agreement of HRV assessments between an electrocardiogram (ECG) and PEP.

Methods

In total, 60 healthy adults were recruited to participate in this study (mean age 22.3 years [SD 3.0 years], mean height 168.4 cm [SD 8.0 cm], mean body weight 64.2 kg [SD 11.5 kg]). A 5-minute resting HRV measurement was recorded via ECG and PEP in a sitting position. Standard deviation of normal R-R interval (SDNN), root mean square of successive R-R interval (RMSSD), proportion of NN50 divided by the total number of RR intervals (pNN50), normalized very-low–frequency power (nVLF), normalized low-frequency power (nLF), and normalized high-frequency power (nHF) were analyzed within 9 time segments of HRV recordings: 0-1 minute, 1-2 minutes, 2-3 minutes, 3-4 minutes, 4-5 minutes, 0-2 minutes, 0-3 minutes, 0-4 minutes, and 0-5 minutes (standard). Standardized differences (ES), intraclass correlation coefficients (ICC), and the Spearman product-moment correlation were used to compare the validity and reliability of each time segment to the standard measurement (0-5 minutes). Limits of agreement were assessed by using Bland-Altman plot analysis.

Results

Compared to standard measures in both ECG and PEP, pNN50, SDNN, and RMSSD variables showed trivial ES (<0.2) and very large to nearly perfect ICC and Spearman correlation coefficient values in all time segments (>0.8). The nVLF, nLF, and nHF demonstrated a variation of ES (from trivial to small effects, 0.01-0.40), ICC (from moderate to nearly perfect, 0.39-0.96), and Spearman correlation coefficient values (from moderate to nearly perfect, 0.40-0.96). Furthermore, the Bland-Altman plots showed relatively narrow values of mean difference between the ECG and PEP after consecutive 1-minute recordings for SDNN, RMSSD, and pNN50. Acceptable limits of agreement were found after consecutive 3-minute recordings for nLF and nHF.

Conclusions

Using the PEP app to facilitate a 1-minute ultra–short-term recording is suggested for time-domain HRV indices (SDNN, RMSSD, and pNN50) to interpret autonomic functions during stabilization. When using frequency-domain HRV indices (nLF and nHF) via the PEP app, a recording of at least 3 minutes is needed for accurate measurement.

Minimal Stabilization Time for Ultra-short Heart Rate Variability Measurements in Professional Soccer

The main aims of this study were: 1) to compare 1-minute RMSSD measurements using different stabilization times between them and also with the criterion; and 2) to determine the agreement between every 1-minute RMSSD measurement with the criterion in professional soccer players. Seven hundred eighteen HRV measurements from professional soccer players were taken. HRV was calculated from 5 to 10 minutes (criterion) and from 1-minute windows with different pre-stabilization times. Friedman and post-hoc tests were applied to compare 1-minute and criterion measurements. Effect size was considered to describe magnitude of change. To determine agreement, Spearman’s correlation was applied, and Bland–Altman analysis was also done between each ultra-short HRV time window and the 5-minute HRV criterion period. The 1-minute HRV without any pre-stabilization time was the only one different from all the other 1-minute measurements that included 1 or more minutes of pre-stabilization (p<0.001). One-minute HRV measurements with 1 or more minutes of pre-stabilisation were highly correlated with those for the criterion period. One-minute HRV without pre-stabilization showed the lowest correlation and the highest bias from the criterion. It is concluded that 1-minute HRV measurements with a prior 1-minute or longer pre-stabilization time are valid to measure HRV in professional male soccer players.

Effect of a Blend of Zingiber officinale Roscoe and Bixa orellana L. Herbal Supplement on the Recovery of Delayed-Onset Muscle Soreness Induced by Unaccustomed Eccentric Resistance Training: A Randomized, Triple-Blind, Placebo-Controlled Trial

BACKGROUND

There is an increasing interest in the use of eccentric muscle exercise to improve physical condition, especially with regards to its health-related benefits. However, it is known that unaccustomed eccentric exercise causes muscle damage and delayed pain, commonly defined as "delayed onset muscle soreness" (DOMS). The efficacy of herbal preparations in subjects suffering from DOMS has been reported in a few previous studies with small or moderate outcome measures related to muscle recovery. The present study aimed to evaluate the effects of a polyherbal mixture containing whole Zingiber officinale Roscoe and Bixa orellana L., powders called ReWin(d), in young male athletes suffering from DOMS induced by a 1 h session of plyometric exercises.

METHODS

Thirty-three young male athletes participated in this randomized, Triple-blind, placebo-controlled trial: 17 of them assigned to the ReWin(d) group and 16 of them to the placebo group. Creatine kinase (CK) was measured as a muscle damage marker, pain was assessed using the Visual Analog Scale (VAS), muscle performance was measured through half-squat exercise (HS) monitored with an accelerometer (Encoder), and heart rate variability (HRV) was monitored for 5 min with the subjects in the supine position. All determinations were performed before and after the eccentric session and 24, 48, and 72 h after the session.

RESULTS

The eccentric exercise session caused an increase in CK at 24 and 48 h after exercise intervention in both groups (p < 0.001). There was no interaction between groups regarding muscle damage. The pain increased after the training session in both groups (p < 0.001), and a significant interaction was observed between groups at 48 h after exercise (p = 0.004). Lower limb muscular power showed a significant interaction between groups 24 h after exercise (p = 0.049); the placebo group showed a reduction in muscle power compared to the ReWin(d) group. The LF/HF ratio decreased significantly at 72 h after exercise in the herbal group but not in the placebo group.

CONCLUSION

The herbal supplement maintained the maximum power of the lower limbs and attenuated muscle pain.

CLINICAL TRIAL REGISTRATION

www.ClinicalTrials.gov, identifier NCT03961022.

Priming autonomous and controlling motivation and effects on persistence

The present studies examined whether priming distinct motivational states influenced persistence at a task designed to promote repeated failure, and post-task plans for engaging in self-regulatory activity. Two double-blind, between-subject experiments (Study 1: N = 58; Study 2: N = 92) involved participants being randomized to Autonomous Motivation, Controlling Motivation, or Neutral prime conditions using a scrambled-sentence test. Participants then attempted an impossible persistence task that promoted repeated failure. Following, participants reported their plans to engage in exercise. Using frequentist and Bayesian analyses, Study 1, Study 2, and an internal meta-analysis showed no differences in persistence or planned exercise across priming conditions, thus contrasting with previous research. Unanticipated moderation effects or motivational priming effects being smaller than those inputted into a priori power analyses may be the most likely reasons for these findings.

Validity of a Smartphone Application and Chest Strap for Recording RR Intervals at Rest in Athletes

OBJECTIVE

To evaluate the accuracy of the smartphone application (app) HRV Expert (CardioMood) and a chest strap (H10 Polar) for recording R-R intervals compared with electrocardiogram (ECG).

METHODS

A total of 31 male recreational runners (age 36.1 [6.3] y) volunteered for this study. R-R intervals were recorded simultaneously by the smartphone app and ECG for 5 minutes to analyze heart-rate variability in both the supine and sitting positions. Time-domain indexes (heart rate, mean R-R, SD of RR intervals, count of successive normal R-R intervals differing by more than 50 ms, percentage of successive normal R-R intervals differing by more than 50 ms, and root mean square of successive differences between normal R-R intervals), frequency-domain indexes (low frequency, normalized low frequency, high frequency, normalized high frequency, low-frequency to high-frequency ratio, and very low frequency), and nonlinear indexes (SD of instantaneous beat-to-beat variability and long-term SD of continuous R-R intervals) were compared by unpaired t test, Pearson correlation, simple linear regression, and Bland-Altman plot to evaluate the agreement between the devices.

RESULTS

High similarity with P value varying between .97 and 1.0 in both positions was found. The correlation coefficient of the heart-rate-variability indexes was perfect (r = 1.0; P = .00) for all variables. The constant error, standard error of estimation, and limits of agreement between ECG and the smartphone app were considered small.

CONCLUSION

The smartphone app and chest strap provide excellent ECG compliance for all variables in the time domain, frequency domain, and nonlinear indexes, regardless of the assessed position. Therefore, the smartphone app replaces ECG for any heart-rate-variability analysis in runners.

Does firefighters' physical fitness influence their cardiac parasympathetic reactivation? Analysis with post-exercise heart rate variability and ultra-short-term measures

Purpose. This study assessed the influence of firefighters' physical fitness on performances and parasympathetic reactivation in rescue interventions, and tested the validity of post-exercise ultra-short-term heart rate variability. Methods. Twenty-four firefighters were assigned to two groups based on their fitness and performed three simulated interventions. The mean completion time was recorded. The post-exercise root mean square of successive differences of R-R intervals (LnRMSSD) was determined from both criterion (between 5 and 10 min) and ultra-short-term (every 1-min segment from minutes 0-6) analyses. Results. Completion time was better for the highest fitness group in the three simulated interventions while post-exercise LnRMSSD was not influenced by the firefighters' fitness. Reliability between ultra-short-term and criterion analyses differed between the segments tested; minute 5-6 revealed the highest intra-class correlations (0.86-0.97). Concerning sensitivity of both analyses, the criterion analysis revealed differences between the three rescue interventions and the fitness test, but these results were not observed with ultra-short-term measures. Conclusions. Fitness was associated with firefighters' performances but not with parasympathetic reactivation in the firefighting intervention. The ultra-short-term measures do not seem to be a suitable post-exercise LnRMSSD analysis because of the low sensitivity to reveal differences among exercise conditions.

Heart rate variability as a possible predictor of sport performance in junior rhythmic gymnastics

BACKGROUND: Heart rate variability may reveal sensitive information about the athletes’ physiological adaptation when exercising for sport performance. OBJECTIVE: The aim of this study was to demonstrate whether heart rate variability (HRV) measurements were able to predict sport results and determine which type of measurements, at rest or during routines, were relevant in anticipating the performance. METHOD: Ten female gymnasts, aged 11–14 years old, and 16 age-matched non-active adolescents participated in this study. HRV was measured at rest for 10 minutes and throughout the training routines one week prior to competition. Correlations and multivariate analysis determined the parameters predicting performance. Significance was set at p⩽ 0.05. Results: At rest, the gymnasts displayed higher HRV values than controls. At rest, sympathetic parameters correlated with sport results whereas no correlation was observed during routines. The magnitude of the predictive factors highlighted the importance of Ln SD2 (coefficient =-117, 95CI -130 to -106), Ln RMSSD (coefficient =-24.5, 95CI -29.2 to -19.8), Ln pNN50 (coefficient =-10.7, 95CI -11.5 to -9.9), and Ln Total power (coefficient =-2.5, 95CI -13.4 to -11.5). CONCLUSIONS: HRV at rest may predict results in competition, being a complementary tool for coaches.

Heart Rate Variability in College Football Players throughout Preseason Camp in the Heat

We aimed to characterize cardiac-autonomic responses to a 13-day preseason camp in the heat among an American college football team. Players were categorized as linemen (n=10) and non-linemen (n=18). RHR, natural logarithm of the root-mean square of successive differences multiplied by twenty (LnRMSSD), and subjective wellbeing (LnWellness) were acquired daily. Effect sizes±90% confidence interval showed that for linemen, LnRMSSD decreased (moderate) on day 2 (71.2±10.4) and increased (moderate) on day 12 (87.1±11.2) relative to day 1 (77.9±11.2) while RHR decreased (small-moderate) on days 6, 7, and 12 (67.7±9.3-70.4±5.5 b∙min-1) relative to day 1 (77.1±10.1 b∙min-1). For non-linemen, LnRMSSD increased (small-large) on days 3-5, 7, 12, and 13 (83.4±6.8-87.6±8.5) relative to day 1 (80.0±6.5) while RHR decreased (small-large) on days 3-9, 12, and 13 (62.1±5.2-67.9±8.1 b∙min-1) relative to day 1 (70.8±6.2 b∙min-1). Decrements in LnWellness were observed on days 4-10 and 13 for linemen (moderate) and on days 6-9, 12, and 13 for non-linemen (small-moderate). Despite reductions in LnWellness, cardiac-autonomic parameters demonstrated responses consistent with heat-acclimation, which possibly attenuated fatigue-related decrements.

A low-complexity PPG pulse detection method for accurate estimation of the pulse rate variability (PRV) during sudden decreases in the signal amplitude

BACKGROUND

One of the biggest obstacles to reliable pulse rate variability (PRV) analysis is the erroneous detection of photoplethysmographic (PPG) pulses. Among all the disturbances that may hinder pulse detection, the ripples appearing at the smooth segments of the PPG signal can become a serious problem when the amplitude of the signal decreases considerably.

OBJECTIVE

To present a low-complexity PPG pulse detection method for reliable PRV estimation under conditions in which a sudden decrease in the amplitude of the PPG signal can be expected.

APPROACH

2-min ECG and PPG data (sampling rate at 500 Hz) were obtained from thirty healthy subjects, who were asked to take a deep inspiration to provoke a sudden amplitude decrease (SAD) of the PPG signal. After introducing a new parameter denoted as C, through which it is possible to jump over the ripples hindering the accurate detection of the systolic peaks, 500 Hz-sampled PPG recordings were down-sampled (400, 300, 200 and 100 Hz) to investigate the effect of the sampling rate on pulse detection. For ECG recordings, automatic R-peak detection was performed by the Pan and Tompkins (PT) algorithm, whereas PPG pulse detection was performed by the well-known maximum of the first derivative (M1D) and the proposed method, once the C-value for best detection results on 500 Hz-sampled PPG recordings was found. The agreement between heart rate variability (HRV) and PRVs estimated from each pulse detection method was assessed and the correlation between HRV and PRV-derived indexes was computed for comparison.

MAIN RESULTS

The proposed method can perform well on PPG-SAD segments, provided that the proper value of the parameter C is used. Moreover, a good agreement between HRV and PRV series, as well as lower relative errors and higher correlation coefficients between HRV and PRV indexes, were achieved by the proposed pulse detection method during SADs.

SIGNIFICANCE

Results show that the proposed method can dynamically adapt to circumstances in which a decrease in the amplitude of the PPG signal can be expected, providing continuous systolic peak detection and reliable PRV estimation under those conditions. However, more extensive testing under a wide range of conditions is needed to perform a more rigorous validation.

Determination of minimal recording period to assess resting heart rate variability during pregnancy

Traditionally, resting heart rate variability (rHRV) is measured for 10 min using the last 5 min for analyses (e.g., criterion period). It is unknown whether the measurement period can be shortened in pregnant women as there are currently no established standards. We aimed to compare shorter time segments (e.g., from the 1st to 10th minutes) of the parasympathetic index natural logarithm transformation of root mean square of successive R–R differences (Ln rMSSD) with the criterion period in pregnant and nonpregnant women. Twelve pregnant (age: 30.8 ± 3.4 years; gestational age: 20.1 ± 5.0 weeks) and 15 nonpregnant women (age: 29.8 ± 4.0 years) were included. rHRV was measured using a portable heart rate monitor for 10 min while sitting. Ln rMSSD difference/agreement between shorter time segments and criterion period was analyzed. The result observed between the 4th–5th minutes was the shortest time segment not different from/highly agreed with the criterion period in pregnant women (difference [95% confidence interval (CI)]: −0.10 [−0.22 to 0.02]/bias ± 1.96 × SD: −0.06 [−0.38 to 0.25]). In nonpregnant women, the 2nd–3rd-minute segment was the shortest with similar results (difference [95% CI]: −0.04 [−0.15 to 0.07]/bias ± 1.96 × SD: −0.03 [−0.39 to 0.32]). The Ln rMSSD was found to be stable from the 5th–10th minutes and the 3rd–10th minutes in pregnant and nonpregnant women, respectively. A shortened rHRV assessment can increase its applicability in clinical/exercise-training settings.

Novelty Ln rMSSD can be measured for 5 min in pregnant women, with the last 1-min segment analyzed. The last 1-min segment from 3 min can be used for rHRV measurement in nonpregnant women. The shortened rHRV assessment can facilitate its applicability in clinical/exercise-training settings.

The Accuracy of Acquiring Heart Rate Variability from Portable Devices: A Systematic Review and Meta-Analysis

BACKGROUND

Advancements in wearable technology have provided practitioners and researchers with the ability to conveniently measure various health and/or fitness indices. Specifically, portable devices have been devised for convenient recordings of heart rate variability (HRV). Yet, their accuracies remain questionable.

OBJECTIVE

The aim was to quantify the accuracy of portable devices compared to electrocardiography (ECG) for measuring a multitude of HRV metrics and to identify potential moderators of this effect.

METHODS

This meta-analysis was conducted in accordance with the Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA) statement. Articles published before July 29, 2017 were located via four electronic databases using a combination of the terms related to HRV and validity. Separate effect sizes (ESs), defined as the absolute standardized difference between the HRV value recorded using the portable device compared to ECG, were generated for each HRV metric (ten metrics analyzed in total). A multivariate, multi-level model, incorporating random-effects assumptions, was utilized to quantify the mean ES and 95% confidence interval (CI) and explore potential moderators.

RESULTS

Twenty-three studies yielded 301 effects and revealed that HRV measurements acquired from portable devices differed from those obtained from ECG (ES = 0.23, 95% CI 0.05-0.42), although this effect was small and highly heterogeneous (I² = 78.6%, 95% CI 76.2-80.7). Moderator analysis revealed that HRV metric (p <0.001), position (p = 0.033), and biological sex (β = 0.45, 95% CI 0.30-0.61; p <0.001), but not portable device, modulated the degree of absolute error. Within metric, absolute error was significantly higher when expressed as standard deviation of all normal-normal (R-R) intervals (SDNN) (ES = 0.44) compared to any other metric, but was no longer significantly different after a sensitivity analysis removed outliers. Likewise, the error associated with the tilt/recovery position was significantly higher than any other position and remained significantly different without outliers in the model.

CONCLUSIONS

Our results suggest that HRV measurements acquired using portable devices demonstrate a small amount of absolute error when compared to ECG. However, this small error is acceptable when considering the improved practicality and compliance of HRV measurements acquired through portable devices in the field setting. Practitioners and researchers should consider the cost-benefit along with the simplicity of the measurement when attempting to increase compliance in acquiring HRV measurements.

Ultra-short-term and Short-term Heart Rate Variability Recording during Training Camps and an International Tournament in U-20 National Futsal Players

The aim of this study was to examine ultra-short-term and short-term heart rate variability (HRV) in under-20 (U-20) national futsal players during pre-tournament training camps and an official tournament. Fourteen male U-20 national futsal players (age = 18.07 ± 0.73 yrs; height = 169.57 ± 8.40 cm; body weight = 64.51 ± 12.19 kg; body fat = 12.42% ± 3.18%) were recruited to participate in this study. Early morning 10 min resting HRV, Borg CR-10 scale session rating of perceived exertion (sRPE), and general wellness questionnaire were used to evaluate autonomic function, training load, and recovery status, respectively. Log-transformed root mean square of successive normal-to-normal interval differences (LnRMSSD) was used to compare the first 30 s, first 1 min, first 2 min, first 3 min, and first 4 min with standard 5 min LnRMSSD. Mean (LnRMSSD_mean) and coefficient of variation (LnRMSSD_cv) of LnRMSSD were used to compare the different time segments of HRV analysis. The result of LnRMSSD_mean showed nearly perfect reliability and relatively small bias in all comparisons. In contrast, LnRMSSD_cv showed nearly perfect reliability and relatively small bias from 2-4 min time segments in all study periods. In conclusion, for accuracy of HRV measures, 30 s or 1 min ultra-short-term record of LnRMSSD_mean and short-term record of LnRMSSD_cv of at least 2 min during the training camps are recommended in U-20 national futsal players.

Consecutive non-training days over a weekend for assessing cardiac parasympathetic variation in response to accumulated exercise stress

Purpose: To examine the association between day-to-day resting cardiac parasympathetic variability over consecutive non-training days (i.e. weekend) and accumulated exercise stress when quantified using indices of cardiovascular strain. Methods: Twelve international calibre female field hockey players training as part of a national team were participants over a four-week mesocycle prior to a 2016 Olympic qualifying tournament. On-field exercise stress was examined using heart rate (HR) dynamics and quantified as; (1) training load and (2) time (min) spent above anaerobic threshold. The square root of the mean squared differences of successive cardiac cycles (R-R intervals) recorded on Saturday and Sunday were individually calculated and log-transformed prior to being averaged (Ln rMSSDweekend). Day-to-day variation in Ln rMSSD over the weekend was expressed using the coefficient of variation (Ln rMSSD_CV). Non-linear regression analysis examined the association between accumulated exercise stress and Ln rMSSD_CV. Results: A quadratic association between each index of exercise stress and Ln rMSSD_CV was identified. After converting the coefficient of determination into a correlation coefficient (90% CL), the respective association between Ln rMSSD_CV and training load (AU); r = 0.40 (0.16:0.59) and time above threshold; r = 0.35 (0.06:0.59) were observed. Conclusion: Ln rMSSD_CV derived over consecutive non-training days displayed a moderate, yet significant association between accumulated exercise stress when expressed as global or high-intensity indices of cardiovascular strain. Weekend assessments may offer a practical and appropriate juncture between microcycles to assess the magnitude of perturbation in cardiac autonomic homeostasis prior to entering subsequent training periods.

Intra-Individual Variation of HRV during Orthostatic Challenge in Elite Male Field Hockey Players

The purpose of this study was to examine the intra-individual variation of heart rate variability (HRV) and heart rate using an orthostatic challenge in elite male athletes during a training camp. Heart rate (variability) was measured upon waking. Log-transformed HRV metrics were evaluated in three segments (first min discarded for stabilization): 0-3 min supine, 3-6 min supine, and standing. Heart rate was assessed while supine, 15 s after standing and average final 30 s standing (Rusko protocol). A RM-ANOVA compared intra-individual means, standard deviations (SD) and coefficients of variation (CV%) for HRV and heart rate. The intraclass correlation coefficient (ICC) and standard error of measurement (SEmeas) were used for relative and absolute reliability, respectively. Time and frequency domain HRV metrics had low variation (CV% <8.5%; SEmeas% ≤4.0%) for 0-3 min supine which was not improved during 3-6 min. Standing HRV had lower ICC and higher SEmeas than supine values. Variability and reliability outcomes for heart rate were comparable to log-transformed HRV metrics. This study uniquely describes the intra-individual variation of HRV metrics during an orthostatic challenge and demonstrated low variability in this cohort of elite male athletes. These data can be helpful for identifying when true individual changes occur for the autonomic nervous system indices in supine and standing positions.

Heart Rate Variability, Neuromuscular and Perceptual Recovery Following Resistance Training

We quantified associations between changes in heart rate variability (HRV), neuromuscular and perceptual recovery following intense resistance training (RT). Adult males (n = 10) with >1 year RT experience performed six sets to failure with 90% of 10 repetition maximum in the squat, bench press, and pull-down. Changes (∆) from pre- to immediately (IP), 24 and 48 h post-RT were calculated for neuromuscular performance markers (counter-movement jump peak power and mean concentric bench press and squat velocity with load corresponding to 1.0 m∙s⁻¹) and perceived recovery and soreness scales. Post-waking natural logarithm of the root-mean square of successive differences (LnRMSSD) in supine and standing positions were recorded pre-RT (5 day baseline), IP and two mornings post-RT. All parameters worsened at IP (p < 0.05). LnRMSSD measures were not different from baseline by 24 h. Neuromuscular markers were not different from pre-RT by 48 h. Perceptual measures remained suppressed at 48 h. No significant associations among ∆ variables were observed (p = 0.052–0.978). These data show varying timeframes of recovery for HRV, neuromuscular and perceptual markers at the group and individual level. Thus, post-RT recovery testing should be specific and the status of one metric should not be used to infer that of another.

A Randomized, 8-Week Study of the Effects of Extended-Release Paliperidone and Olanzapine on Heart Rate Variability in Patients With Schizophrenia

PURPOSE

This study aimed to explore the effect of extended-release paliperidone (paliperidone ER) and olanzapine on heart rate variability (HRV) in patients with schizophrenia.

METHODS

A total of 106 patients with schizophrenia diagnosed by the Diagnostic and Statistical Manual of Mental Disorders (Fifth Edition) were randomly divided into the paliperidone ER group or the olanzapine group for an 8-week clinical trial, with 53 patients in each group. The time domain and frequency domain analyses including the SD of all the R-R intervals in 24 hours (SDNN), the SD of the mean value of all the normal R-R intervals in every 5-minute interval within 24 hours (SDANN index), the mean value of the SD of all the normal R-R intervals in every 5-minute interval within 24 hours (SDNN index), the root mean square of successive R-R differences, the percentage of adjacent R-R intervals that differ by more than 50 milliseconds, high-frequency power (HF), low-frequency power (LF), and LF/HF were adopted to assess the HRV of patients at baseline and after treatment for 8 weeks in each group. The Positive and Negative Symptom Scale was used to evaluate the clinical efficacy. The incidence rates of adverse reactions were also calculated.

RESULTS

In total, 48 patients in the paliperidone ER group and 45 patients in the olanzapine group completed the entire 8-week treatment. The SDNN, SDNN index, and SDANN index in the olanzapine group were significantly lower than those in the paliperidone ER group (P < 0.05) after treatment for 8 weeks, whereas their mean LF level was higher than that in the paliperidone ER group (P < 0.05) after completion of treatment. Patients in the olanzapine group showed a significant decrease in the SDNN, SDANN index, and SDNN index as well as a statistical increase in the LF and LF/HF in comparison with the pretreatment values (P < 0.05), whereas patients in the paliperidone ER group showed a decrease in the SDANN index and a statistical increase in the LF in comparison with the pretreatment values (P < 0.05).

CONCLUSION

The HRV of patients with schizophrenia changes when they are administered with paliperidone ER or olanzapine, and more attention should be paid to their cardiac autonomic function when using these 2 antipsychotics.

Exergame-Driven High-Intensity Interval Training in Untrained Community Dwelling Older Adults: A Formative One Group Quasi- Experimental Feasibility Trial

Purpose

To investigate the feasibility of an exergame-driven high-intensity interval training (HIIT) and its effects on cardiovascular fitness in untrained community dwelling older adults.

Methods

Twelve older participants [10 women, age 72.3 (SD: 4.44) years] performed a high-intensity interval exergame intervention three times a week for 4 weeks. Data was acquired during two baseline and one final measurement. Feasibility outcomes included attrition, adherence, acceptability [Technology Acceptance Model Questionnaire (TAM)], usability [System Usability Scale (SUS)], and enjoyment of exergaming. Furthermore, participants' physical activity levels pre and post intervention were compared to physical activity levels for similar types of training. The secondary outcome was exercise capacity [heart rate at rest (HRrest), heart rate variability (HRV), maximum heart rate (HRmax), and maximum workload (W, in watt)] evaluated through maximal exercise testing.

Results

Eleven participants completed the study (8% attrition), without any adverse events. Adherence to the HIIT intervention was 91% and participants showed high acceptance of the intervention with TAM scores between 5.8 and 6.7 points. User satisfaction was rated as excellent (SUS total score: 93.5 of 100) and the overall enjoyment of exergaming scored 4.5 of 5 possible points. Total exercise time ranged from 19 to 35 min with a mean of 30.8 (SD: 3.6) min. Actual high-intensity exercise time showed consistency with the target exercise time in 98% percent of trainings. Eighty-six percent of high-intensity intervals met the targeted intensity range (>70-90% of HRmax). Thirty-six percent of the recovery periods were completed with a heart rate above the target range of 50-70% of HRmax. Maximum workload (W) during the incremental exercise test post-training increased significantly compared to the baseline measurements one and two (p = 0.032, effect size r = 0.77 and p = 0.012, r = 0.87).

Conclusion

High-intensity interval training through exergaming is feasible, safe, and shows high usability and acceptance in community dwelling older people. Exergame-driven HIIT had a significant effect on maximum power output on an incremental exercise test. A more extensive exergame intervention period, higher work to recovery ratios as well as a higher-intensity activity should be considered in future projects.

Effect of Overload and Tapering on Individual Heart Rate Variability, Stress Tolerance, and Intermittent Running Performance in Soccer Players During a Preseason

Figueiredo, DH, Figueiredo, DH, Moreira, A, Gonçalves, HR, and Stanganelli, LCR. Effect of overload and tapering on individual heart rate variability, stress tolerance, and intermittent running performance in soccer players during a preseason. J Strength Cond Res 33(5): 1222-1231, 2019-This study evaluates the weekly natural log of the root-mean-square difference of successive R-R intervals (lnRMSSDmean), its coefficient of variation (lnRMSSDcv), training load (TL), stress tolerance (ST), and changes in intermittent running performance in response to a 2-week overload (OL) followed by a 1-week taper (TP) during a preseason. Additionally, we determined the relationships between these variables. Ultra-short lnRMSSD, psychometric responses, and ratings of perceived exertion were evaluated daily among 16 under-19 soccer players. At the end of each training phase, the athletes performed the Yo-Yo Intermittent Recovery test level 1 (Yo-Yo). Group analysis showed a decrease in lnRMSSDmean and ST, increases in lnRMSSDcv, and decreases in the Yo-Yo during OL, with a return to baseline levels and a trivial increase in the Yo-Yo during TP. Small to very large correlations were found between lnRMSSDmean and lnRMSSDcv values, with changes in Yo-Yo, TL, monotony, and strain during the preseason (r values ranging from -0.27 to 0.82). No correlation was found between lnRMSSD responses and ST. During OL, athletes with decreases in lnRMSSDmean and increases in lnRMSSDcv accumulated higher perceived TL, with higher monotony and overall stress, and presented a decrease in ST and intermittent running performance, interpreted as a negative adaptation in response to the maintenance of higher TL. During TP, these responses were reversed, leading to an increase in intermittent running performance. In addition, subjective measures of ST may be used to provide early indicators of training adaptation in soccer players.

Home Monitoring of Heart Rate as a Predictor of Imminent Cardiovascular Events

Introduction: Previous studies have documented that day-to-day variability of heart rate (HR) has prognostic significance for cardiovascular (CV) events in general population. It is unknown how HR dynamics variate before imminent CV event in patients with coronary artery disease (CAD). Our aim was to study day-to-day variation in HR dynamics before the occurrence of CV event in patients with initially stable CAD.

Methods: Forty-four patients with angiographically documented CAD from ARTEMIS study measured R-R intervals on a weekly basis at home for 2 years. Home measurements were performed in controlled conditions (3 min at supine and sitting) 1–2 times per week. Eleven patients had a CV event (7 acute coronary syndromes, 1 cardiac death, 2 new onset of arrhythmia needing hospitalization and 1 stroke), which occurred 11 ± 7 months after enrolment. Mean R-R interval was analyzed prospectively from the home measurements. For the patients with new CV event, average, and standard deviation (SD) of the mean R-R interval over 8 weeks preceding the CV event were calculated. For the patients without new CV event, corresponding period was determined by the median follow-up at the occurrence of new CV event.

Results: There were no differences in the mean R-R interval analyzed over 8 weeks between the patients with and without new CV event. The variability of mean R-R interval over 8 weeks was greater in the patients with new CV event compared to the patients without new CV event at the supine (95 ± 34 vs. 59 ± 26 ms, p < 0.001) and sitting positions (92 ± 28 vs. 62 ± 24 ms, p < 0.001).

Conclusion: Day-to-day variability of mean R-R interval is greater before the new CV event in CAD patients suggesting to a more unstable cardiac autonomic regulation preceding these events.

A New Algorithm to Reduce and Individualize HRV Recording Time

The aim of the present work was to propose a Smartphone algorithm to analyze, in real time, the evolution of Heart Rate Variability (HRV) in order to individualize and reduce the recording time according to the specificities of each user. During HRV recording, a new RMSSD value is calculated each time a new RR is captured. The recording process stops once an acceptable stability of HRV is reached. This new method was tested on 3 groups of 15 subjects (cardiac patients, sedentary employees and national-level athletes) and compared with the gold standard method (5 min HRV recording time). The RMSSD indices provided by the short method and by the gold standard method (respectively 62.1 ± 43.7 ms vs. 62.7 ± 44.1 ms) showed no significant differences. In addition, a very strong correlation was observed between RMSSD values obtained by the 2 methods (n = 45; R = 0.998; p < 0.001). Routine duration of the new method was significantly shorter with a time-savings of 2 min (178 ± 51 s vs. 300 s; p < 0.05). This new algorithm seems to adapt perfectly to each subject, and it can detect the stability phase for HRV measurements during the recording process. Algorithm provides an adapted and personal routine duration that can evolve each day depending on parameters such as fatigue or stress level that are known to influence HRV. This solution can be easily implemented in a smartphone application and seems particularly suitable for performing daily HRV monitoring in field conditions.