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Introduction: The parasympathetically derived marker of heart rate variability, root mean square of successive R-R differences (RMSSD), and the daily fluctuations as measured by the coefficient of variation (RMSSDCV) may be useful for tracking training adaptations in athletic populations. These vagally derived markers of heart rate variability may be especially pertinent when simultaneously considering a female athlete's menstrual cycle. Purpose: The purpose of this study was to observe the perturbations in RMSSDCV, while considering RMSSD, across a season in the presence and absence of menses with training load in female collegiate rowers. Methods: Thirty-six (20 [1] y, 25.6 [3.4] kg·m−2) National Collegiate Athletic Association Division I female rowers were monitored for 18 consecutive weeks across a full season. Seated, ultrashortened RMSSD measurements were obtained by the rowers on at least 3 mornings per week using a smartphone photoplethysmography device. Following the RMSSD measurement, athletes indicated the presence or absence of menstruation within the application. Individual meters rowed that week and sessions rate of perceived exertion were obtained to quantify training load. Results: Longitudinal mixed-effects modeling demonstrated a significant effect of menses and time, while also considering RMSSD, such that those who were on their period had a significantly greater RMSSDCV than those who were not (11.2% vs 7.5%, respectively; P <.001). These changes were independent of meters rowed, sessions rate of perceived exertion, body mass index, birth-control use, and years of rowing experience, which were all nonsignificant predictors of RMSSDCgV (P >.05). Conclusion: The presence of menses appears to significantly impact RMSSDCV when also considering RMSSD, which may allow coaches to consider individualized training plans accordingly. [ABSTRACT FROM AUTHOR]

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. [ABSTRACT FROM AUTHOR]

Background Hearing loss is highly prevalent in older ages and has several health consequences. Some cardiovascular risk factors are associated with worse hearing at older ages. Still, the role of midlife leisure-time physical activity (PA) as a risk factor for hearing loss is yet to be investigated. Methods Among 3 198 participants of the Atherosclerosis Risk in Communities study, we investigated the associations of midlife and change from mid- to late-life PA (assessed via modified Baecke questionnaire) with hearing loss (audiometric battery [worse-ear pure-tone average, and speech-in-noise test]) at older ages. We used regression analyses, adjusted for demographics, medical conditions, and noise exposure, to estimate differences in hearing between those who met and did not meet PA recommendations at midlife and at late life. Results A total of 1 386 (43.3%) participants met PA recommendations at midlife. These participants, compared to those who did not meet recommendations, had lower (better) pure-tone average by 1.51 (0.46, 2.55) decibels, identified 0.37 (0.01, 0.74) more words (better score) in the speech-in-noise test, and had a lower relative risk of having hearing loss at older ages (eg, relative risk ratio for severe hearing loss vs normal hearing = 0.70 [0.52, 0.95]). Similarly, those who persistently met PA recommendations from mid- to late life had, compared with those who did not, a better hearing at older ages. Conclusions Meeting PA public health recommendations in midlife and mid- to late life was associated with better hearing at older ages and reduced risk of hearing loss. Promoting adequate levels of PA may be an essential component of hearing care. [ABSTRACT FROM AUTHOR]

Most blood flow restriction (BFR) devices use a set pressure to occlude flow, and the effects of these devices on post-exercise recovery in the distal musculature have not been thoroughly explored. This study evaluates the effect of BFR on fatigue during resistance exercise in the musculature distal to the occlusion site. Twenty participants (age: 23 ± 4 years) completed two exercise sessions with or without BFR in a crossover-design. The participants performed 3 sets of 15 repetitions of maximum ankle plantarflexion (PF) and dorsiflexion (DF) on an isokinetic dynamometer. Eighty percent limb occlusion pressure (LOP) was applied to the thigh during BFR. Isokinetic dynamometer metrics were evaluated during the exercise. Gastrocnemius cross sectional area (CSA) was measured preexercise and post-exercise. A toe-tap test, average step length test, and counter-movement jump test were employed to evaluate fatigue and recovery from pre-exercise to post-exercise. Repeated measures ANOVA was used to determine significant differences. BFR caused a significant reduction in peak torque (P = 0.009), average force (P<0.001), total work for PF (P<0.001), and elevated RPE (P<0.001) during the exercise compared to the control. A significantly lower (P<0.001) number of toe taps were performed after the BFR (28.9 ± 1.7) condition when compared to the control (42.7 ± 1.3). CSA was increased pre-exercise vs. post-exercise for BFR only and was significantly elevated compared to the control (P = 0.009). BFR appears to induce fatigue, likely through accumulation of metabolic stress as evidenced by the enhanced muscular swelling and rapid recovery rate post-exercise. [ABSTRACT FROM AUTHOR]

Flatt, AA, Hornikel, B, Nakamura, FY, and Esco, MR. Effect of competitive status and experience on heart rate variability profiles in collegiate sprint-swimmers. J Strength Cond Res 36(10): 2898–2904, 2022—Interindividual differences in training history may be a determinant of heart rate variability (HRV) profiles in collegiate sprint-swimmers and may account for differences observed between elite and subelite athletes. We therefore compared HRV profiles among national-level and conference-level sprint-swimmers while accounting for individual swim-training history. Twenty-eight short-distance swimmers (18 men and 10 women) recorded postwaking HRV throughout a 4-week standardized training period. The 4-week mean (M) and coefficient of variation (CV, a marker of daily fluctuation) were calculated for resting heart rate (RHR) and the natural logarithm of the root mean square of successive differences (LnRMSSD). Swimmers were categorized as national-level (n = 12) or conference-level (n = 16) competitors. Years of competitive experience was documented for each individual to index training history. p < 0.05 was considered statistically significant. No sex-related differences were observed for any variables (p > 0.05). LnRMSSDM (effect size [ES] = 0.95), LnRMSSDCV (ES = −1.18), RHRCV (ES = −1.05), and competitive experience (ES = 1.23) differed between status groups (p < 0.05). Accounting for multicollinearity between competitive experience and LnRMSSD variables (p < 0.05), competitive experience remained associated with LnRMSSDM (r = 0.44, p = 0.02). With competitive experience included as a covariate, differences in LnRMSSDM between status groups disappeared (p > 0.05, ES = 0.31). National-level swimmers exhibit higher and more stable LnRMSSD than that of their conference-level teammates throughout standardized training. Differences in trend characteristics were attributed to training age. This information may assist practitioners with interpreting interindividual differences in HRV profiles throughout training periods among a mixed roster of athletes. [ABSTRACT FROM AUTHOR]

The purpose of this study was to investigate lower limb blood flow responses under varying blood flow restriction (BFR) pressures based on individualized limb occlusion pressures (LOP) using a commonly used occlusion device. Twenty-nine participants (65.5% female, 23.8 ± 4.7 years) volunteered for this study. An 11.5cm tourniquet was placed around participants' right proximal thigh, followed by an automated LOP measurement (207.1 ± 29.4mmHg). Doppler ultrasound was used to assess posterior tibial artery blood flow at rest, followed by 10% increments of LOP (10-90% LOP) in a randomized order. All data were collected during a single 90-minute laboratory visit. Friedman's and one-way repeated-measures ANOVAs were used to examine potential differences in vessel diameter, volumetric blood flow (VolFlow), and reduction in VolFlow relative to rest (%Rel) between relative pressures. No differences in vessel diameter were observed between rest and all relative pressures (all p < .05). Significant reductions from rest in VolFlow and %Rel were first observed at 50% LOP and 40% LOP, respectively. VolFlow at 80% LOP, a commonly used occlusion pressure in the legs, was not significantly different from 60% ( p = .88), 70% ( p = .20), or 90% ( p = 1.00) LOP. Findings indicate a minimal threshold pressure of 50%LOP may be required to elicit a significant decrease in arterial blood flow at rest when utilizing the 11.5cm Delfi PTSII tourniquet system.