Heart Rate Variability Changes From Traditional vs. Ultra-Short-Term Recordings in Relation to Preseason Training Load and Performance in Futsal Players

The short-term relation between load and acute psychophysiological responses in football: a meta-analysis and methodological considerations

Relations between load and acute psychophysiological responses have been widely studied in football. However, due to the large heterogeneity in contexts, operationalization, and results, the direction and strength of these relations remain unclear. In this meta-analysis, we examine the relation between load and typical acute (i.e. within one week) responses - wellbeing, recovery, and heart rate measures - in football players from all football codes (soccer, rugby, futsal, American football, and Australian rules football). We consulted PubMed, Web of Science, and CINAHL up to the 19th of June 2024, and included 62 articles and 1,474 participants in the meta-analysis. Subsequently, we estimated 12 meta-analysis models and applied meta-regression models to explore the influence of several moderators. Significant relations were found between load and overall wellbeing (r = -0.33 [95%CI: -0.48; -0.19]), muscle soreness (r = -0.36 [95%CI: -0.49; -0.24]), fatigue (r = -0.41 [95%CI: -0.56; -0.26]), sleep quality (r = -0.21 [95%CI: -0.31; -0.10]), and stress (r = -0.16 [95%CI: -0.26; -0.06]). Given the high risk of bias, inconsistency (wide prediction intervals), and imprecision, the certainty in these findings based on the GRADE assessment is very low. Additionally, the high risk of bias scores indicates that the overall quality of the included studies is low. In conclusion, this meta-analysis provides comprehensive information on the acute responses of the athlete to load, and directions for improvement of the quality of future studies.

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.

Heart rate variability, recovery and stress analysis of an elite rally driver and co-driver during a competition period

To ensure both optimal health and performances, monitoring physiological and psychological states is of main importance for athletes. It is well known that monitoring heart rate variability and using validated questionnaires is useful for monitoring both the health and training status of athletes of different sports. Motorsports such as rally require high levels of physical and mental preparation thus information about psychophysiological status of rally athletes is fundamental. The aim of this study was to assess the autonomic regulation, stress, recovery conditions of one driver and one co-driver competing at the Italian National Rally Championship during their competition period. Heart rate variability parameters, acute recovery and stress states were assessed the day before, during the two days of race and the day following the races. Results showed that driver and co-driver had a sharp decrease of mean RR intervals, root mean square of successive differences between normal heartbeats, and standard deviation of the N-N interval during race days, while the stress index showed the inverse trend, and this behaviour was clearly visible in the Poincaré plots and power spectrum density graphs. The acute recovery and stress states questionnaire showed significant differences in recovery and stress scoring for the driver but not for the co-driver, although the trends were similar. This study describes the psychophysiological demands of a rally competition period suggesting that a daily evaluation of heart rate variability, recovery, stress states is useful for monitoring health status in rally athletes and could be implemented to make decision about training and recovery strategies.

The Validity of Ultra-Short-Term Heart Rate Variability during Cycling Exercise

Ultra-short-term heart rate variability (HRV) has been validated in the resting state, but its validity during exercise is unclear. This study aimed to examine the validity in ultra-short-term HRV during exercise considering the different exercise intensities. HRVs of twenty-nine healthy adults were measured during incremental cycle exercise tests. HRV parameters (Time-, frequency-domain and non-linear) corresponding to each of the 20% (low), 50% (moderate), and 80% (high) peak oxygen uptakes were compared between the different time segments of HRV analysis (180 s (sec) segment vs. 30, 60, 90, and 120-sec segments). Overall, the differences (bias) between ultra-short-term HRVs increased as the time segment became shorter. In moderate- and high-intensity exercises, the differences in ultra-short-term HRV were more significant than in low intensity exercise. Thus, we discovered that the validity of ultra-short-term HRV differed with the duration of the time segment and exercise intensities. However, the ultra-short-term HRV is feasible in the cycling exercise, and we determined some optimal time duration for HRV analysis for across exercise intensities during the incremental cycling exercise.

Intraindividual Relationships Between Training Loads and Heart-Rate Variability in High-Level Female Futsal Players: A Longitudinal Study

PURPOSE

To investigate the internal training loads of a professional Spanish female futsal team throughout 26 weeks of training including preseason and in-season weeks and verify the impact of training period and/or training load magnitudes on heart-rate variability responses. Furthermore, we aimed to assess, intraindividually, the relationship between training load and the coefficient of variation (CV) of weekly natural log of the root mean square difference of successive normal interbeat (RR) intervals (lnRMSSDCV), obtained from ∼5 measures per week, and recorded in the seated position.

METHODS

A within-subject design involved 12 high-level outfield female futsal players (mean [SD] age: 23.9 [3.4] y).

RESULTS

lnRMSSD was significantly lower and lnRMSSDCV was significantly higher during the preseason (weeks 1-6) compared to in-season (weeks 7-26) (P < .001). Individually, players presented moderate to large negative correlations between lnRMSSDCV and lnRMSSD during the 26 weeks of observation. Correlations ranged between rplayer4 = -.41 (95% CI, -.69 to -.02) and rplayer12 = -.55 (-.78 to -.18). Players also presented moderate to very large positive correlations between lnRMSSDCV and session rating of perceived exertion. Correlations ranged between rplayer7 = .41 (.04 to .71) and rplayer1 = .71 (.45 to .86).

CONCLUSION

Professional female futsal players in this study presented increased lnRMSSD and reduced lnRMSSDCV during 20 weeks into the competitive season compared to 6 weeks of preseason. Furthermore, lnRMSSDCV was negatively associated with lnRMSSD on an intraindividual basis. Finally, higher internal training loads were positively correlated with lnRMSSDCV, indicating that heart-rate variability is responsive to weekly training loads.

Evaluating the Typical Day-to-Day Variability of WHOOP-Derived Heart Rate Variability in Olympic Water Polo Athletes

Heart rate (HR) and HR variability (HRV) can be used to infer readiness to perform exercise in athletic populations. Advancements in the photoplethysmography technology of wearable devices such as WHOOP allow for the frequent and convenient measurement of HR and HRV, and therefore enhanced application in athletes. However, it is important that the reliability of such technology is acceptable prior to its application in practical settings. Eleven elite male water polo players (age 28.8 ± 5.3 years [mean ± standard deviation]; height 190.3 ± 3.8 cm; body mass 95.0 ± 6.9 kg; international matches 117.9 ± 92.1) collected their HR and HRV daily via a WHOOP strap (WHOOP 3.0, CB Rank, Boston, MA, USA) over 16 weeks ahead of the 2021 Tokyo Olympic Games. The WHOOP strap quantified HR and HRV via wrist-based photoplethysmography during overnight sleep periods. The weekly (i.e., 7-day) coefficient of variation in lnRMSSD (lnRMSSD_CV) and HR (HR_CV) was calculated as a measure of day-to-day variability in lnRMSSD and HR, and presented as a mean of the entire recording period. The mean weekly lnRMSSD_CV and HR_CV over the 16-week period was 5.4 ± 0.7% (mean ± 95% confidence intervals) and 7.6 ± 1.3%, respectively. The day-to-day variability in WHOOP-derived lnRMSSD and HR is within or below the range of day-to-day variability in alternative lnRMSSD (~3-13%) and HR (~10-11%) assessment protocols, indicating that the assessment of HR and HRV by WHOOP does not introduce any more variability than that which is naturally present in these variables.

Tracking the Fatigue Status after a Resistance Exercise through Different Parameters

The purpose of the study was to investigate the sensitivity of back squat bar velocity, isometric mid-thigh pull, heart rate variability parameters, perceived recovery scale and step counts for tracking the muscular fatigue time-course (reduction in countermovement jump [CMJ] performance) after strenuous acute lower limb resistance exercise. Sixteen healthy men performed heart rate variability assessment, perceived recovery scale, CMJ, back squat bar velocity, isometric mid-thigh pull, and daily step counts before and 24 h, 48 h and 72 h post a strenuous acute lower limb resistance exercise (8×10 repetitions). The CMJ height decreased at 24 and 48 h after exercise session (p≤0.017), evidencing the muscular fatigue. The perceived recovery scale presented lower values compared to baseline until 72 h after exercise session (p<0.001 for all). The heart rate variability parameters and step counts were not significantly different across time. At 24 h post, only mean force of mid-thigh pull was decreased (p=0.044), while at 48 h post, only peak force of mid-thigh pull was decreased (p=0.020). On the last day (72 h), only bar velocity (mean) presented reduction (p=0.022). Therefore, the perceived recovery scale was the only variable sensible to tracking muscular fatigue, i. e. presenting a similar time-course to CMJ height.

The Most Demanding Exercise in Different Training Tasks in Professional Female Futsal: A Mid-Season Study through Principal Component Analysis

The contextual factors related to training tasks can play an important role in how a player performs and, subsequently, in how a player trains to face a competition. To date, there has been no study that has investigated the most demanding exercise in different training tasks in female futsal. Therefore, this study aimed to determine the most demanding efforts during different training tasks in a cohort study conducted in professional biological women futsal players using principal component analysis (PCA). A total of 14 elite women futsal players (age = 24.34 ± 4.51 years; height = 1.65 ± 0.60 m; body mass = 63.20 ± 5.65 kg) participated in this study. Seventy training sessions of an elite professional women’s team were registered over five months (pre-season and in-season). Different types of exercises were grouped into six clusters: preventive exercises; analytical situations; exercises in midcourt; exercises in ¾ of the court; exercises in full court; superiorities/inferiorities. Each exercise cluster was composed of 5–7 principal components (PCs), considering from 1 to 5 main variables forming each, explaining from 65 to 75% of the physical total variance. A total of 13–19 sub-variables explained the players’ efforts in each training task group. The first PCs to explain the total variance of training load were as follows: preventive exercises (accelerations; ~31%); analytical situations (impacts; ~23%); exercises in midcourt (high-intensity efforts; ~28%); exercises in ¾ of the court (~27%) and superiorities/inferiorities (~26%) (aerobic/anaerobic components); exercises in full court (anaerobic efforts; ~24%). The PCs extracted from each exercise cluster provide evidence that may assist researchers and coaches during training load monitoring. The descriptive values of the training load support a scientific base to assist coaches in the planning of training schedules.

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.

Monitoring Training Load, Immune-Endocrine, Autonomic Nervous System Responses, and Swimming Performance in Women's Water Polo

Purpose: The purposes of the study were to: i) verify the variations in training load and the subsequent effects on swimming performance parameters, biochemical parameters, and autonomic nervous activity during a water polo season; ii) investigate the sensitivity of physiological markers in tracking training load and performance variations, and iii) verify the overreaching prevalence. Method: The training load of 20 female water polo players was monitored (using the session rating of perceived exertion method [sRPE], training monotony, and strain), and the lactate minimum speed (LMS), repeated sprint ability (RSA), plasma hormone and glutamine concentration, salivary immunoglobulin A (SIgA), and heart rate variability (lnRMSSD) were evaluated during the season. Result: The training load parameters were higher in the competitive cycle (p ≤ 0.002). The LMS improved only in the general cycle from baseline (p = .015), while the RSA best time improved in the general (p = .002) and specific cycles (p = .012) from baseline and deteriorated in the competitive from general cycle (p = .008). The SIgA secretion rate presented a reduction only in the specific cycle from baseline (p = .032), while the lnRMSSD increased in the general (p = .038) and competitive (p < .001) cycles from baseline. Five athletes were diagnosed as overreaching state. Conclusion: Therefore, the physiological markers (i.e., plasma hormone and glutamine concentration, SIgA, and lnRMSSD) showed little sensitivity to detect changes in training load and swimming performance. The higher training loads applied in the competitive cycle seem to limit swimming performance gains.

Selected vs. Non-Selected Under-20 National Futsal Players: Differences between Physical Performance and Training Intensity Experienced in Training Camps

The aim of this study was two-fold: (i) analyze the variations in the physical fitness of selected and non-selected under-20 male national futsal players; and (ii) analyze the variations in training intensity monitored during training camps. Thirty-three Taiwan under-20 national futsal players were monitored for training intensity during 18 training camps. They were divided into two groups: selected (n = 14) and non-selected (n = 17) players. The physical assessments included the following measures: body mass, distance covered at Yo-Yo intermittent recovery test Level 1, final velocity at 30-15 Intermittent Fitness Test (30-15 IFT), standing long jump, maximum heart rate (HR), and 1-min sit-up. The training intensity was monitored using the rate of perceived exertion (RPE), HR at different intensity zones, and locomotor demands measured at different speed thresholds. The results revealed that the selected players were significantly faster in the 15-m sprint with ball (p = 0.001) and 30-m sprint (p = 0.001). Additionally, the selected players presented significantly greater HRaverage and time spent above 90% maximum HR during the three-to-six-day training camps (p < 0.05) compared to the non-selected players. Interestingly, the NS demonstrated a greater number of sprints during the training camps (p = 0.001), while the selected players presented greater distance/minute and average speed (p = 0.001). A regression analysis showed that the distance/minute and average speed was a significant predictor of maximum HR in the selected players. As conclusions, the physical fitness outcomes are different between the selected and non-selected national futsal players. The selected players spent more time in high intensity HR demands in training sessions.

Heart Rate Variability-Guided Training for Enhancing Cardiac-Vagal Modulation, Aerobic Fitness, and Endurance Performance: A Methodological Systematic Review with Meta-Analysis

PURPOSE

This systematic review with meta-analysis was conducted to establish whether heart rate variability (HRV)-guided training enhances cardiac-vagal modulation, aerobic fitness, or endurance performance to a greater extent than predefined training while accounting for methodological factors.

METHODS

We searched Web of Science Core Collection, Pubmed, and Embase databases up to October 2020. A random-effects model of standardized mean difference (SMD) was estimated for each outcome measure. Chi-square and the I2 index were used to evaluate the degree of homogeneity.

RESULTS

Accounting for methodological factors, HRV-guided training was superior for enhancing vagal-related HRV indices (SMD+ = 0.50 (95% confidence interval (CI) = 0.09, 0.91)), but not resting HR (SMD+ = 0.04 (95% CI = -0.34, 0.43)). Consistently small but non-significant (p > 0.05) SMDs in favor of HRV-guided training were observed for enhancing maximal aerobic capacity (SMD+ = 0.20 (95% CI = -0.07, 0.47)), aerobic capacity at second ventilatory threshold (SMD+ = 0.26 (95% CI = -0.05, 0.57)), and endurance performance (SMD+ = 0.20 (95% CI = -0.09, 0.48)), versus predefined training. No heterogeneity was found for any of the analyzed aerobic fitness and endurance performance outcomes.

CONCLUSION

Best methodological practices pertaining to HRV index selection, recording position, and approaches for establishing baseline reference values and daily changes (i.e., fixed or rolling HRV averages) require further study. HRV-guided training may be more effective than predefined training for maintaining and improving vagal-mediated HRV, with less likelihood of negative responses. However, if HRV-guided training is superior to predefined training for producing group-level improvements in fitness and performance, current data suggest it is only by a small margin.

Wrist-Based Photoplethysmography Assessment of Heart Rate and Heart Rate Variability: Validation of WHOOP

Heart rate (HR) and HR variability (HRV) infer readiness to perform exercise in athletic populations. Technological advancements have facilitated HR and HRV quantification via photoplethysmography (PPG). This study evaluated the validity of WHOOP’s PPG-derived HR and HRV against electrocardiogram-derived (ECG) measures. HR and HRV were assessed via HR and HRV were assessed via WHOOP 2.0 and ECG over 15 opportunities during October–December 2018. WHOOP-derived pulse-to-pulse (PP) intervals were edited with WHOOP’s proprietary filter, in addition to various filter strengths via Kubios HRV software. HR and HRV (Ln RMSSD) were quantified for each filter strength. Agreement was assessed via bias and limits of agreement (LOA), and contextualised using smallest worthwhile change (SWC) and coefficient of variation (CV). Regardless of filter strength, bias (≤0.39 ± 0.38%) and LOA (≤1.56%) in HR were lower than the CV (10–11%) and SWC (5–5.5%) for this parameter. For Ln RMSSD, bias (1.66 ± 1.80%) and LOA (±5.93%) were lowest for a 200 ms filter and WHOOP’s proprietary filter, which approached or exceeded the CV (3–13%) and SWC (1.5–6.5%) for this parameter. Acceptable agreement was found between WHOOP- and ECG-derived HR. Bias and LOA in Ln RMSSD approached or exceeded the SWC/CV for this variable and should be interpreted against its own level of bias precision.

Characterization of Reproductive and Morphological Variables in Female Elite Futsal Players

We aimed to characterize the age of onset of training, age at menarche, menstrual periodicity, and performance perception during the menstrual cycle and examined the impact of these reproductive variables on body composition, morphology, and body weight satisfaction in Brazilian elite futsal players. The study consisted of 115 female Brazilian elite futsal players from the top national teams. Data were collected during the twentieth Women's Brazil Futsal Cup. Players were interviewed and self-reported their age of onset of training, age at menarche, menstrual periodicity, and the menstrual period, where they performed best. We also asked for what they considered to be their ideal body weight as well as information related to their training (i.e., volume and frequency). Subsequently, anthropometric measurements (i.e., body mass, height, circumferences, diameters, and skinfold thickness) were performed to estimate the body composition and determine morphological characteristics (e.g., somatotype). Fifty-nine (53.2%) players were postmenarche-trained and 52 (46.8%) were premenarche-trained. Eighteen (16.2%), 65 (58.6%), and 28 (25.2%) were classified as early, normal, and late menarche, respectively. Only 11 (9.6%) and 1 (0.9%) had irregular menstrual cycles and were amenorrheic, respectively. Seventy-three (69.5%), 23 (21.9%), and 9 (8.6%) reported that their game performance was the best at the follicular phase, menses, and luteal phase of the menstrual cycle, respectively. No associations between the four reproductive-related variables were found. Postmenarche-trained players had significant lower age at menarche and higher percentage body fat. The somatotype profile registered lower ectomorphy rate for the postmenarche-trained participants after controlling for covariates. Early menarche group presented higher sum of six skinfold thickness and endomorphy rate compared to normal and late menarche groups. No differences were found when menstrual periodicity groups and best performance groups were compared, except for higher femur width in the regular menstrual cycle group compared to the irregular one. The association between body weight satisfaction and the four reproductive-related variables were not observed. Premenarche-trained Brazilian elite futsal players had the menarche later than the postmenarche-trained athletes. Most of the participants had menarche age classified as "normal," presented "regular" menstrual cycles and perceived to perform better during the follicular phase of the menstrual cycle.

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.

HIIT Models in Addition to Training Load and Heart Rate Variability Are Related With Physiological and Performance Adaptations After 10-Weeks of Training in Young Futsal Players

INTRODUCTION

The present study aimed to investigate the effects of two high-intensity interval training (HIIT) shuttle-run-based models, over 10 weeks on aerobic, anaerobic, and neuromuscular parameters, and the association of the training load and heart rate variability (HRV) with the change in the measures in young futsal players.

METHODS

Eleven young male futsal players (age: 18.5 ± 1.1 years; body mass: 70.5 ± 5.7 kg) participated in this study. This pre-post study design was performed during a typical 10 weeks training period. HIIT sessions were conducted at 86% (HIIT86; n = 6) and 100% (HIIT100; n = 5) of peak speed of the FIET. Additionally, friendly and official matches, technical-tactical and strength-power training sessions were performed. Before and after the training period, all players performed the FIET, treadmill incremental, repeated sprint ability (RSA), sprint 15-m, and vertical jump tests (CMJ and SJ), and the HRV was measured. Training load (TL) was monitored using the session rating of perceived effort. Data analysis was carried out using Bayesian inference methods.

RESULTS

The HIIT86 model showed clear improvements for the peak oxygen uptake (VO2peak), peak speed in the treadmill incremental test, first and second ventilatory thresholds, RSA best and mean times, CMJ, and SJ. The HIIT100 model presented distinct advances in VO2peak, peak speed in the treadmill incremental test, RSA mean time, and CMJ. Between HIIT models comparisons showed more favorable probabilities of improvement for HIIT86 than HIIT100 model in all parameters. TL data and HIIT models strongly explained the changes in the RSA mean and best times (R 2 = 0.71 and 0.87, respectively), as well as HRV changes, and HIIT models explained positively VO2peak changes (R 2 = 0.72). All other changes in the parameters were low to moderately explained.

CONCLUSION

The HIIT86 proved to be more effective for improving aerobic, RSA, and neuromuscular parameters than HIIT100 during a typical 10-week futsal training period. So, strength and conditioning specialists prescribing shuttle-run intermittent exercises at submaximal intensities can manage the individual acceleration load imposed on athlete increasing or decreasing either the set duration or the frequency of change of direction during HIIT programming.

Do heart rate variability is relationed to endurance performance in female futsal players?

abstract The study aimed to verify the correlation between resting heart rate variability (HRVrest) and endurance performance in female futsal players, as well as to evaluate the reliability of this parasympathetic autonomic marker. A total of 16 female futsal players (age: 22 ± 3 years; VO2max: 42.3 ± 2.0 ml.kg-1.min-1) were evaluated during the first week of preseason training. Vagal modulation was evaluated from the HRVrest (i.e., log-transformed root mean square of successive R-R interval differences - Ln-RMSSD) for two consecutive days, while endurance performance was evaluated by the Yo-Yo Intermittent Recovery Test, Level 1 (Yo-Yo IR1). Pearson correlation was used to analyze the relationship between the variables. Strong correlation between the HRVrest index and endurance performance (r = 0.643; p = 0.007). Reliability was tested through the intraclass correlation coefficient, coefficient of variation (CV), and Bland-Altman analysis of the agreement. Furthermore, acceptable repeatability of HRVrest, but with great inter-subject variability (ICC = 0.670, 95%CI = 0.056-0.885, CV = 15.8%). The current study demonstrated a strong correlation between Ln-RMSSD and endurance performance, and despite the acceptable values of intrasubject reliability, HRVrest presented high inter-individual variability in female futsal players.

Physical and Physiological Match-Play Demands and Player Characteristics in Futsal: A Systematic Review

Futsal, also known as five-a-side indoor soccer, is a team-sport that is becoming increasingly popular. In fact, the number of futsal-related investigations is growing in recent years. This review aimed to summarize the scientific literature addressing the match-play demands from the following four dimensions: time-motion/external load analysis and physiological, neuromuscular, and biochemical responses to competition. Additionally, it aimed to describe the anthropometric, physiological, and neuromuscular characteristics of elite and sub-elite male futsal players, contemplating the differences between competition levels. The literature indicates that elite futsal players cover greater total distance with higher intensities and perform a greater number of sprints during match-play when compared to sub-elite players. The physiological demands during competition are high (average intensity of ≥85% maximal heart rate and ~80% maximum oxygen uptake [VO2max]), with decrements between the two halves. Research suggests that neuromuscular function decreased and hormonal responses increased up to 24 h after the match. Considering anthropometric characteristics, players present low percentage of body fat, which seems commonplace among athletes from different on-court positions and competition levels. Elite players display greater values and at VO2max with respect to sub-elite competitors. Little is known regarding elite and sub-elite futsal players' neuromuscular abilities (strength, jumping, sprinting, and change of direction [COD]). However, it appears that elite players present better sprinting abilities compared to lower-level athletes. Futsal players aiming to compete at the highest level should focus on developing maximal speed, lower-body power and strength, aerobic capacity, and lean muscle mass.

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.

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.

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.

Using the Rating of Perceived Exertion and Heart Rate to Quantify Training Intensity in Female Soccer Players: Validity and Utility

Costa, JA, Brito, J, Nakamura, FY, Figueiredo, P, and Rebelo, A. Using the rating of perceived exertion and heart rate to quantify training intensity in female soccer players: validity and utility. J Strength Cond Res XX(X): 000-000, 2019-The aims of this study were as follows: (a) to analyze associations between session rating of perceived exertion (sRPE) and training impulse (TRIMP); (b) to verify whether significantly different ranges of percentage of heart rate peak (%HRpeak) would be reached in each discrete RPE category; and (c) to investigate the amount of time spent >90% of HRpeak and associated intraplayer and interplayer variability during soccer technical training sessions with similar contents and duration. This was a single-group observational study that measured the internal training load during 6 weeks of the competitive period in 17 high-level female soccer players. All training sessions started around 9 PM. and lasted on average 94 ± 5 minutes. During each training session, RPE, sRPE, TRIMP, HRex (%HRpeak), and time spent at >90% of HRpeak were assessed. A very large correlation was found between sRPE and TRIMP (r = 0.78; 95% confidence interval: [0.74-0.82]). Significant differences were observed between %HRpeak associated with each RPE value (i.e., RPE = 2 arbitrary unit [68%; 65-69% of %HRpeak]; RPE 3 [72%; 69-75%]; RPE 4 [79%; 76-82%]; RPE 5 [84; 81-87%]; χ = 73.34; df = 3; P < 0.001). Intraplayer and interplayer coefficients of variation for the time spent >90% of HRpeak (∼8% of training time, ∼7 minutes per session) during training sessions were 73 and 92%, respectively. In conclusion, it was confirmed that sRPE and TRIMP displayed good convergent validity, and different %HRpeak were observed for each discrete RPE. However, because of the high variability in the time >90% of HRpeak, careful monitoring of individual exercises should be performed to ensure the desired training stimulus for each player.

Intra-individual variability of sleep and nocturnal cardiac autonomic activity in elite female soccer players during an international tournament

PURPOSE

To describe individual sleeping patterns and nocturnal cardiac autonomic activity of National team female soccer players during an international tournament.

MATERIALS AND METHODS

Twenty elite female soccer players (aged 25.2±3.1 years) wore wrist actigraph units and heart rate (HR) monitors during night-sleep throughout 9 consecutive days (6 day-time training sessions [DT], 2 day-time matches [DM], and 1 evening-time match [EM]) of an international tournament. Training and match loads were monitored using the session-rating of perceived exertion (s-RPE) and wearable 18-Hz GPS (total distance covered [TD], training and match exposure time, and high-speed running [HSR]) to characterize training and match loads.

RESULTS

Individually, s-RPE, TD, exposure time, and HSR during training sessions ranged from 20 to 680 arbitrary units (AU), 892 to 5176 m, 20 to 76 min, and 80 to 1140 m, respectively. During matches, s-RPE, TD, exposure time, and HSR ranged from 149 to 876 AU, 2236 to 11210 m, 20 to 98 min, and 629 to 3213 m, respectively. Individually, players slept less than recommended (<7 hours) on several days of the tournament, especially after EM (n = 8; TST ranging between 6:00-6:54 h). Total sleep time coefficient of variation (CV) ranged between 3.1 and 18.7%. However, all players presented good sleep quality (i.e., sleep efficiency ≥75%; individual range between: 75-98%) on each day of the tournament. Most of the players presented small fluctuations in nocturnal cardiac autonomic activity (individual nocturnal heart rate variability [HRV] ranged from 3.91-5.37 ms and HRV CV ranged from 2.8-9.0%), while two players presented higher HRV CV (11.5 and 11.7%; respectively).

CONCLUSION

Overall, this study highlights the substantial individual variability in sleep and HRV measures, suggesting the adoption of an individual approach to monitor sleep, training and match loads and recovery, to better understand how players cope with highly demanding competitions.

Importance of Agility Performance in Professional Futsal Players; Reliability and Applicability of Newly Developed Testing Protocols

The purpose of this study was to determine the inter- and intra-testing reliability of newly developed tests of the change of direction speed (CODS) and reactive agility (RAG) in competitive futsal players. Additionally, the developed tests were evaluated for their validity with regard to the differentiation of two performance-levels. Thirty-two professional male futsal players (age = 26.22 ± 5.22 years; body height = 182.13 ± 5.99 cm, body mass = 77.43 ± 8.00 kg) participated in the study. The sample was divided into two groups based on their level of futsal performance: A top-level-group (n = 12) and a team-level-group (n = 20). The variables included body height, mass, body mass index, a sprint over a 10-m distance (S10M), and eight newly developed futsal specific CODS and RAG tests. The CODS and RAG tests were performed by dribbling the balls (CODS_D and RAG_D) and without dribbling (CODS_T and RAG_T), and the performances on the dominant and non-dominant sides were observed separately. All CODS, and RAG tests performed on dominant side and RAG_T tests performed on the non-dominant side had good inter-testing (CV = 5–8%; ICC = 0.76–0.89) and intra-testing (CV = 4–9%; ICC = 0.77–0.91) reliability. However, RAG_D performed on the non-dominant side was not reliable (ICC = 0.60, CV = 10%). The top-level-players outperformed the team-level-players in the CODS and RAG tests that involved dribbling (t-test: 4.28 and 2.40, p < 0.05; effect sizes (ES): 0.81 and 1.5, respectively), while the team-level players achieved better results in the CODS_T (t-test: 2.08, p < 0.05; ES: 0.60). The proposed CODS and RAG tests that involved dribbling over a 3.2-m distance, especially on the dominant side, appeared to be reliable, as well as valid for distinguishing the performance level in futsal players.