Log-transformed Root Mean Square Research Articles

Effects of voluntary exercise and electrical muscle stimulation on reaction time in the Go/No-Go task.

Acute exercise improves cognitive performance. However, it remains unclear what triggers cognitive improvement. Electrical muscle stimulation (EMS) facilitates the examination of physiological changes derived from peripheral muscle contraction during exercise. Thus, we compared the effects of EMS and voluntary exercise at low- or moderate-intensity on reaction time (RT) in a cognitive task to understand the contribution of central and peripheral physiological factors to RT improvement. Twenty-four young, healthy male participants performed a Go/No-Go task before and after EMS/exercise. In the EMS condition, EMS was applied to the lower limb muscles. In the low-intensity exercise condition, the participants cycled an ergometer while maintaining their heart rate (HR) at the similar level during EMS. In the moderate-intensity exercise condition, exercise intensity corresponded to ratings of perceived exertion of 13/20. The natural log-transformed root mean square of successive differences between adjacent inter-beat (R-R) intervals (LnRMSSD), which predominantly reflects parasympathetic HR modulation, was calculated before and during EMS/exercise. RT improved following moderate-intensity exercise (p = 0.002, Cohen' d = 0.694), but not following EMS (p = 0.107, Cohen' d = 0.342) and low-intensity exercise (p = 0.076, Cohen' d = 0.380). Repeated measures correlation analysis revealed that RT was correlated with LnRMSSD (Rrm(23) = 0.599, p = 0.002) in the moderate-intensity exercise condition. These findings suggest that the amount of central neural activity and exercise pressor reflex may be crucial for RT improvement. RT improvement following moderate-intensity exercise may, at least partly, be associated with enhanced sympathetic nervous system activity.

Effects of three weeks base training at moderate simulated altitude with or without hypoxic residence on exercise capacity and physiological adaptations in well-trained male runners.

To test the hypothesis that 'live high-base train high-interval train low' (HiHiLo) altitude training, compared to 'live low-train high' (LoHi), yields greater benefits on performance and physiological adaptations. Sixteen young male middle-distance runners (age, 17.0 ± 1.5 y; body mass, 58.8 ± 4.9 kg; body height, 176.3 ± 4.3 cm; training years, 3-5 y; training distance per week, 30-60 km.wk-1) with a peak oxygen uptake averaging ~65 ml.min-1.kg-1 trained in a normobaric hypoxia chamber (simulated altitude of ~2,500 m, monitored by heart rate ~170 bpm; thrice weekly) for 3 weeks. During this period, the HiHiLo group (n = 8) stayed in normobaric hypoxia (at ~2,800 m; 10 h.day-1), while the LoHi group (n = 8) resided near sea level. Before and immediately after the intervention, peak oxygen uptake and exercise-induced arterial hypoxemia responses (incremental cycle test) as well as running performance and time-domain heart rate variability (5-km time trial) were assessed. Hematological variables were monitored at baseline and on days 1, 7, 14 and 21 during the intervention. Peak oxygen uptake and running performance did not differ before and after the intervention in either group (all P > 0.05). Exercise-induced arterial hypoxemia responses, measured both at submaximal (240 W) and maximal loads during the incremental test, and log-transformed root mean square of successive R-R intervals during the 4-min post-run recovery period, did not change (all P > 0.05). Hematocrit, mean reticulocyte absolute count and reticulocyte percentage increased above baseline levels on day 21 of the intervention (all P < 0.001), irrespective of group. Well-trained runners undertaking base training at moderate simulated altitude for 3 weeks, with or without hypoxic residence, showed no performance improvement, also with unchanged time-domain heart rate variability and exercise-induced arterial hypoxemia responses.

Heart rate variability and risk of agitation in Alzheimer's disease: the Atherosclerosis Risk in Communities Study.

Agitation in Alzheimer's disease is common and may be related to impaired emotion regulation capacity. Heart rate variability, a proposed index of autonomic and emotion regulation neural network integrity, could be associated with agitation propensity in Alzheimer's disease. We used the Atherosclerosis Risk in Communities Study cohort data, collected over seven visits spanning over two decades, to investigate whether heart rate variability (change) was associated with agitation risk in individuals clinically diagnosed with dementia due to Alzheimer's disease. Agitation (absence/presence) at Visit 5, the primary outcome, was based on the Neuropsychiatric Inventory agitation/aggression subscale, or a composite score comprising the total number of agitation/aggression, irritability, disinhibition and aberrant motor behaviour subscales present. Visit 1-5 heart rate variability measures were the log-transformed root mean square of successive differences in R-R intervals and standard deviation of normal-to-normal R-R intervals obtained from resting, supine, standard 12-lead ECGs. To aid interpretability, heart rate variability data were scaled such that model outputs were expressed for each 0.05 log-unit change in heart rate variability (which approximated to the observed difference in heart rate variability with every 5 years of age). Among 456 participants who had dementia, 120 were clinically classified to have dementia solely attributable to Alzheimer's disease. This group showed a positive relationship between heart rate variability and agitation risk in regression models, which was strongest for measures of (potentially vagally mediated) heart rate variability change over the preceding two decades. Here, a 0.05 log-unit of heart rate variability change was associated with an up to 10-fold increase in the odds of agitation and around a half-unit increase in the composite agitation score. Associations persisted after controlling for participants' cognitive status, heart rate (change), sociodemographic factors, co-morbidities and medications with autonomic effects. Further confirmatory studies, incorporating measures of emotion regulation, are needed to support heart rate variability indices as potential agitation propensity markers in Alzheimer's disease and to explore underlying mechanisms as targets for treatment development.

Isotemporal Associations of Device-Measured Sedentary Time and Physical Activity with Cardiac-Autonomic Regulation in Previously Pregnant Women.

High sedentary time (ST) and low physical activity may increase cardiovascular risk, potentially though cardiac-autonomic dysregulation. This study investigated associations of statistically exchanging device-measured ST and physical activity with measures of cardiac-autonomic regulation in previously pregnant women. This cross-sectional, secondary analysis included 286 women (age = 32.6 ± 5.7years; 68% white) measured 7-15years after delivery. ST and light (LPA), moderate (MPA), vigorous (VPA), and moderate-to-vigorous (MVPA) intensity physical activity were measured by ActiGraph GT3X. ST was further partitioned into long (≥ 30min) and short (< 30min) bouts. MVPA was also partitioned into long (≥ 10min) and short (< 10min) bouts. Cardiac-autonomic regulation was assessed by heart rate variability (HRV) (resting heart rate, natural log transformed standard deviation of normal R-R intervals [lnSDNN], natural log-transformed root mean square of successive differences [lnRMSSD]) from a 5-min seated ECG. Progressive isotemporal substitution models adjusted for confounders. Sensitivity analyses removed women with related underlying medical conditions and who did not meet respiration rate criteria. Initial analyses found no significant associations with HRV when exchanging 30min of ST and physical activity (p > 0.05). Yet, replacing long- and short-bout ST with 30min of long-bout MVPA yielded significantly higher (healthier) lnRMSSD (B = 0.063 ± 0.030 and B = 0.056 ± 0.027, respectively; both p < 0.05). Sensitivity analyses strengthened these associations and yielded further associations of higher lnSDNN and lnRMSSD when replacing 30min of short-bout MVPA with equivalent amounts of long-bout MVPA (B = 0.074 ± 0.037 and B = 0.091 ± 0.046, respectively). Replacing ST with long-bout MVPA is a potential strategy to improve cardiac-autonomic function in previously pregnant women.

Effects of active and cold-water immersion recovery strategies on perceived well-being and physical readiness: a crossover study conducted after small-sided soccer games

PurposeThe study investigated the effect of active recovery (AR) and cold-water immersion (CWI) recovery strategies on the speed of recovery after small-sided games (SSGs) in soccer players.MethodsA crossover design was employed to divide 24 male soccer players from a first division Iranian National League (age: 22.3 ± 2.6 years) into 4 experimental conditions: active-active, active-CWI, CWI-active, and CWI-CWI. Heart rate (HR) variations (standard deviation of normal R-R intervals [SDNN], log-transformed root mean square of successive R-R intervals [lnRMSSD]) and self-reported indices (Hooper questionnaire and rate of perceived exertion [RPE]) were measured. Twenty-four hours after SSGs, the players performed one of the recovery strategies. Forty-eight hours after the session, they completed a 20-m sprint test; changes were compared with baseline.ResultsA significant difference in SDNN HR variations between AR and CWI recovery strategies (&lt;i&gt;F&lt;/i&gt; = 4.86, &lt;i&gt;p&lt;/i&gt; = 0.03, ƞ&lt;sup&gt;2&lt;/sup&gt; = 0.31) was noted. Regarding within-experimental condition changes (&lt;i&gt;F&lt;/i&gt; = 60.82, &lt;i&gt;p&lt;/i&gt; = 0.001, ƞ&lt;sup&gt;2&lt;/sup&gt; = 0.85), significant differences were detected when comparing data recorded before SSGs and immediately after SSGs (&lt;i&gt;p&lt;/i&gt; = 0.001), as well as for data recorded before SSGs and immediately after recovery (&lt;i&gt;p&lt;/i&gt; = 0.001). There was also a significant difference in lnRMSSD HR variations when AR and CWI were compared (&lt;i&gt;F&lt;/i&gt; = 2.41, &lt;i&gt;p&lt;/i&gt; = 0.033, ƞ&lt;sup&gt;2&lt;/sup&gt; = 0.29). Within-experimental condition changes (&lt;i&gt;F&lt;/i&gt; = 127.9, &lt;i&gt;p&lt;/i&gt; = 0.001, ƞ&lt;sup&gt;2&lt;/sup&gt; = 0.74) indicated significant differences between data recorded before SSGs and immediately after SSGs (&lt;i&gt;p&lt;/i&gt; = 0.001), as well as between data recorded before SSGs and immediately after recovery (&lt;i&gt;p&lt;/i&gt; = 0.001). No significant difference was found between the SDNN index of HR variability for different recoveries (&lt;i&gt;p&lt;/i&gt; = 0.055, ƞ&lt;sup&gt;2&lt;/sup&gt; = 0.07). Moreover, no significant differences were noted between recovery strategies in terms of Hooper index (&lt;i&gt;p&lt;/i&gt; = 0.832, ƞ&lt;sup&gt;2&lt;/sup&gt; = 0.11), RPE (&lt;i&gt;p&lt;/i&gt; = 0.41, ƞ&lt;sup&gt;2&lt;/sup&gt; = 0.06), or 20-m sprint test (&lt;i&gt;p&lt;/i&gt; = 0.78, ƞ&lt;sup&gt;2&lt;/sup&gt; = 0.02).ConclusionsCWI showed a greater effect than AR in restoring the impaired vagal-related HR variability indices observed immediately after SSGs. However, no advantage was observed between the recovery strategies.

Effects of COVID-19 Lockdown and a Subsequent Retraining Period on Elite Athletes' Workload, Performance, and Autonomic Responses: A Case Series.

To describe the effects of COVID-19 lockdown and a subsequent retraining on the training workloads, autonomic responses, and performance of a group of elite athletes. The training workloads and heart rate variability (assessed through the log-transformed root mean square of successive R-R intervals) of 7 elite badminton players were registered daily during 4weeks of normal training (baseline), 7 to 10weeks of lockdown, and 6 to 8weeks of retraining. Physical performance was assessed at baseline and after each phase by means of a countermovement jump and the estimated squat 1-repetition maximum. A reduction in training workloads was observed in all participants during the lockdown (-63.7%), which was accompanied by a reduced heart rate variability in all but one participant (-2.0%). A significant reduction was also observed for countermovement jump (-6.5%) and 1-repetition maximum performance (-11.5%), which decreased in all but one participant after the lockdown. However, after the retraining phase, all measures returned to similar values to those found at baseline. At the individual level, there were divergent responses, as exemplified by one athlete who attenuated the reduction in training workloads and increased her performance during the lockdown and another one who markedly reduced his workload and performance, and got injured during the retraining phase. Although there seems to be a large interindividual variability, COVID-19 lockdown is likely to impose negative consequences on elite athletes, but these detrimental effects might be avoided by attenuating reductions in training workloads and seem to be overall recovered after 6 to 8weeks of retraining.

Sex-Specific Autonomic Responses to Acute Resistance Exercise.

Background and Objectives: Acute resistance exercise (RE) reduces vagal modulation and increases sympathovagal balance, which increases the risk for arrythmias. Few studies have examined sex differences in autonomic modulation after acute RE. The purpose of this investigation was to examine sex-specific responses to acute RE on autonomic modulation. Materials and Methods: Twenty-one resistance-trained individuals (men n = 11, women n = 10) between the ages of 19 and 25 y were analyzed for autonomic modulation in response to acute RE and a control (CON). Measures of autonomic modulation were collected at rest, 15 (R15), and 30 (R30) min following both conditions. Heart rate (HR), log transformed root mean square of successive differences (lnRMSSD), total power (lnTP), low-frequency power (lnLF), high-frequency power (lnHF), sample entropy (SampEn), and Lempel-Ziv entropy (LZEn) were measured at all time points. A three-way repeated analysis of variance (ANOVA) was used to analyze sex (men, women) across condition (RE, CON) and time (Rest, R15, R30). Results: The results are similar for all heart rate variability (HRV) variables at rest for both conditions (RE, CON). SampEn was significantly higher in men compared to women at rest for both conditions (p = 0.03), with no differences in LZEn (p > 0.05). There were no significant (p > 0.05) three-way interactions on any variables. Condition by time interactions demonstrated that both sexes increase in HR (p = 0.0001) and lnLF/HF ratio (p = 0.001), but decreases in lnRMSSD (p = 0.0001), lnTP (p < 0.0001), lnLF (p < 0.0001), lnHF (p = 0.0001), and LZEn (p = 0.009) at R15 and R30 compared to rest following acute RE and were different from CON. Condition by time interaction (p = 0.017) demonstrated that SampEn was attenuated at R15 compared to rest, and the CON, but not R30 following acute RE. Conclusion: Although SampEn is more complex at rest in men compared to women, autonomic modulation responses between sexes following acute RE appear to be similar.

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.

Caffeine In Conjunction With Resistance Exercise On Vagal Modulation In Resistance-trained Women

PURPOSE: To examine the effects of caffeine alone, or in conjunction, with acute resistance exercise, in resistance-trained women on performance and measures of vagal modulation. METHODS: Eleven resistance-trained women (Age Mean±SD: 24±4yrs) consumed either a placebo (PL) or caffeine (4mg/kg) 72 hours apart, in a double-blind, crossover fashion. Forty-five minutes following supplementation, participants performed two sets of 10 repetitions at 75% 1-repetition maximum (1RM), and one set with repetitions to failure at 70% 1RM on the squat and bench press. Log transformed root mean square of successive differences (lnRMSSD), and high frequency power (lnHF), as well as sample entropy (SampEn), and Lempel-Ziv entropy (LZEn) were assessed at rest (Rest1), 45 minutes post-consumption (Rest2), immediately post-exercise (Post1), and 10 minutes post-exercise (Post2). Two-way ANOVAs were used to analyze the effects of condition (PL, caffeine), across time (Rest1, Rest2, Rec1, Rec2). RESULTS: The repetitions on the fatiguing set were similar between conditions for the squat (p=1.0), and the bench press (p=0.7). There were no significant condition by time effects for vagal tone. There was a significant main effect of time (p=0.0001) for lnRMSSD (Rest1: 4.52±0.73ms; Rest2: 4.48±0.64ms; Rec1: 2.72±0.66ms; Rec2: 2.28±0.55ms) such that it significantly decreased during Rec1 and Rec2 compared to Rest1 and Rest2. There was a significant main effect of time (p=0.0001) for lnHF (Rest1: 8.12±1.23ms2; Rest2: 8.00±1.09ms2; Rec1: 4.79±2.50ms2; Rec2: 4.02±1.02 ms2) with it decreasing at Rec1, and Rec2, compared to Rest1 and Rest2. There was a significant main effect of time (p=0.0001) for SampEn (Rest: Rest1: 1.43±.19; Rest2: 1.40±0.19; Rec1: 1.09±0.32; Rec2: 1.09±0.31) such that SampEn was significantly decreased compared to Rest at Rest2, Rec1 and Rec2. Additionally, there was a significant main effect of time (p=0.004) for LZEn (Rest1: 0.73±.09; Rest2: 0.77±0.06; Rec1: 0.66±0.13; Rec2: 0.54±0.16) with Rec2 being significantly attenuated compared to Rest2. CONCLUSIONS: These data demonstrate that 4mg/kg of caffeine consumption does not have an ergogenic effect. In addition, when performed in conjunction with resistance exercise, it does not further decrease measures of vagal modulation in resistance-trained women.

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 (LnRMSSDmean) and coefficient of variation (LnRMSSDcv) of LnRMSSD were used to compare the different time segments of HRV analysis. The result of LnRMSSDmean showed nearly perfect reliability and relatively small bias in all comparisons. In contrast, LnRMSSDcv 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 LnRMSSDmean and short-term record of LnRMSSDcv of at least 2 min during the training camps are recommended in U-20 national futsal players.

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

Nakamura, FY, Antunes, P, Nunes, C, Costa, JA, Esco, MR, and Travassos, B. Heart rate variability changes from traditional vs. ultra-short-term recordings in relation to preseason training load and performance in futsal players. J Strength Cond Res 34(10): 2974-2981, 2020-The aims of this study were to analyze heart rate variability (HRV) changes in futsal players during preseason training using both "criterion" (10-minute) and ultra-shortened (2-minute) measures, and to determine whether they were related to changes in the Yo-Yo Intermittent Recovery Test, level 1 (Yo-Yo IR1) performance and accumulated training load (TL). Eleven male competitive futsal players (age = 25.19 ± 4.70 years; body mass = 73.15 ± 11.70 kg; and height = 176.90 ± 5.01 cm) volunteered for the study. Data collection took place during the first to the fourth weeks of preseason training. Training load was monitored with session ratings of perceived exertion. The total distance (TD) covered during the Yo-Yo IR1 was recorded during week 1 and week 4. Heart rate variability was measured through the log-transformed root mean square of successive normal-to-normal interval differences using the ultra-short analysis, with its weekly mean (lnRMSSDM) and coefficient of variation (lnRMSSDCV) recorded, and by means of the criterion method (weeks 1 and 4). lnRMSSDM was likely higher at week 4 compared with week 1 using both criterion and ultra-short recordings. Moderate-to-large correlations were found between changes in the lnRMSSDM and lnRMSSDCV values and changes in TL and TD (r values ranged from -0.48 to 0.65). Changes in ultra-short HRV measures (i.e., increase in lnRMSSDM and decrease in lnRMSSDCV) during futsal preseason were associated with increased performance. The players who accumulated higher perceived TLs displayed smaller improvements in the Yo-Yo IR1 performance and HRV.

Autonomic response to a short and long bout of high-intensity functional training

ABSTRACTThe evaluation of Autonomic Nervous System (ANS) recovery following exercise provides insight into the transient stress placed on the cardiovascular system. High-Intensity Functional Training (HIFT) is a form of intense exercise that is prescribed in various modalities and durations; however, little is known about the influence of HIFT duration on ANS recovery. Ten apparently healthy males (28.1 ± 5.4 yrs) performed two HIFT sessions (<5-minute and 15-minute) in a crossover fashion. ANS activity was measured using plasma Epinephrine (E) and Norepineprine (NE); Heart Rate Variability markers of the log transformed Root Mean Square of Successive Differences (lnRMSSD) and High-Frequency power (lnHF). No trial dependent differences were observed in lnRMSSD (p = 0.822), lnHF (p = 0.886), E (p = 0.078), or NE (p = 0.194). A significant main time effect was observed in both trials with a depression in lnRMSSD and lnHF following the trials (p < 0.05) and recovering by 2-hours post (p = 0.141, p > 0.999) respectively. A trial dependent increase in E and NE occurred immediately post (p < 0.05) and recovered by 1-hour post (p > 0.999, p > 0.999) respectively. The HIFT bouts examined within this study demonstrated similar transient strain of the ANS.

Cycling before and after Exhaustion Differently Affects Cardiac Autonomic Control during Heart Rate Matched Exercise.

During cycling before (PRE) and after exhaustion (POST) different modes of autonomic cardiac control might occur due to different interoceptive input and altered influences from higher brain centers. We hypothesized that heart rate variability (HRV) is significantly affected by an interaction of the experimental period (PRE vs. POST) and exercise intensity (HIGH vs. LOW; HIGH = HR > HR at the lactate threshold (HRLT), LOW = HR ≤ HRLT) despite identical average HR.Methods: Fifty healthy volunteers completed an incremental cycling test until exhaustion. Workload started with 30 W at a constant pedaling rate (60 revolutions · min−1) and was gradually increased by 30 W · 5 min−1. Five adjacent 60 s inter-beat (R-R) interval segments from the immediate recovery period (POST 1–5 at 30 W and 60 rpm) were each matched with their HR-corresponding 60 s-segments during the cycle test (PRE 1–5). An analysis of covariance was carried out with one repeated-measures factor (PRE vs. POST exhaustion), one between-subject factor (HIGH vs. LOW intensity) and respiration rate as covariate to test for significant effects (p < 0.050) on the natural log-transformed root mean square of successive differences between adjacent R-R intervals (lnRMSSD60s).Results: LnRMSSD60s was significantly affected by the interaction of experimental period × intensity [F(1, 242) = 30.233, p < 0.001, ηp2 = 0.111]. LnRMSSD60s was higher during PRE compared to POST at LOW intensity (1.6 ± 0.6 vs. 1.4 ± 0.6 ms; p < 0.001). In contrast, at HIGH intensity lnRMSSD60s was lower during PRE compared to POST (1.0 ± 0.4 vs. 1.2 ± 0.4 ms; p < 0.001).Conclusion: Identical net HR during cycling can result from distinct autonomic modulation patterns. Results suggest a pronounced sympathetic-parasympathetic coactivation immediately after the cessation of peak workload compared to HR-matched cycling before exhaustion at HIGH intensity. On the opposite, at LOW intensity cycling, a stronger coactivational cardiac autonomic modulation pattern occurs during PRE-exhaustion if compared to POST-exhaustion cycling. The different autonomic modes during these phases might be the result of different afferent and/or central inputs to the cardiovascular control centers in the brainstem.

Heart rate variability and psychometric responses to overload and tapering in collegiate sprint-swimmers.

The purpose of this study was to evaluate cardiac-parasympathetic and psychometric responses to competition preparation in collegiate sprint-swimmers. Additionally, we aimed to determine the relationship between average vagal activity and its daily fluctuation during each training phase. Observational. Ten Division-1 collegiate sprint-swimmers performed heart rate variability recordings (i.e., log transformed root mean square of successive RR intervals, lnRMSSD) and completed a brief wellness questionnaire with a smartphone application daily after waking. Mean values for psychometrics and lnRMSSD (lnRMSSDmean) as well as the coefficient of variation (lnRMSSDcv) were calculated from 1 week of baseline (BL) followed by 2 weeks of overload (OL) and 2 weeks of tapering (TP) leading up to a championship competition. Competition preparation resulted in improved race times (p<0.01). Moderate decreases in lnRMSSDmean, and Large to Very Large increases in lnRMSSDcv, perceived fatigue and soreness were observed during the OL and returned to BL levels or peaked during TP (p<0.05). Inverse correlations between lnRMSSDmean and lnRMSSDcv were Very Large at BL and OL (p<0.05) but only Moderate at TP (p>0.05). OL training is associated with a reduction and greater daily fluctuation in vagal activity compared with BL, concurrent with decrements in perceived fatigue and muscle soreness. These effects are reversed during TP where these values returned to baseline or peaked leading into successful competition. The strong inverse relationship between average vagal activity and its daily fluctuation weakened during TP.

Agreement Between A Smartphone Pulse Sensor And Electrocardiography For Determining Hrv In Three Different Positions

PURPOSE: To determine the agreement between a smartphone pulse sensor (PS) and electrocardiography (ECG) for determining ultra-short-term heart rate variability (HRV) in three different positions. METHODS: Thirty college-aged men (n = 15) and women (n = 15) volunteered to participate in this study. Sixty second heart rate measures were simultaneously taken with the PS and ECG in supine, seated and standing positions. The log transformed root mean square of successive R-R interval differences (lnRMSSD) was calculated from the PS and ECG. RESULTS: The lnRMSSD values were 81.5 ± 11.7 via PS and 81.6 ± 11.3 via ECG (p = 0.63, Cohen’s d = 0.01) in the supine position, 76.5 ± 8.2 via PS and 77.5 ± 8.2 via ECG (p = 0.007, Cohen’s d = 0.11) in the seated position, and 66.5 ± 9.2 via PS and 67.8 ± 9.1 via ECG (p < 0.001, Cohen’s d = 0.15) in the standing positions. The PS values showed a near perfect correlation to the ECG in all three positions (r values ranged from 0.98 to 0.99). In addition, the limits of agreement (CE ± 1.98 SD) were -0.13 ± 2.83 for the supine values, -0.94± 3.47 for the seated values, and -1.37 ± 3.56 for the standing values. CONCLUSIONS: The results of the study suggest good agreement between the PS and ECG for measuring lnRMSSD in supine, seated, and standing positions. Though significant differences were noted between the two methods in the seated and standing positions, the effect sizes were trivial (i.e., Cohen’s < 0.20). In addition, PS provided tight limits of agreement to the criterion method in all three positions. Therefore, the PS method appears to provide a suitable alternative to ECG for measuring ultra-short-term lnRMSSD.

Initial Weekly HRV Response is Related to the Prospective Change in VO2max in Female Soccer Players.

The aim of this study was to determine whether the early response in weekly measures of HRV, when derived from a smartphone application, were related to the eventual change in VO2max following an off-season training program in female soccer athletes. 9 female collegiate soccer players participated in an 11-week off-season conditioning program. In the week immediately before and after the training program, each participant performed a test on a treadmill to determine maximal oxygen consumption (VO2max). Daily measures of the log-transformed root mean square of successive R-R intervals (lnRMSSD) were performed by the participants throughout week 1 and week 3 of the conditioning program. The mean and coefficient of variation (CV) lnRMSSD values of week 1 showed small (r=- 0.13, p=0.74) and moderate (r=0.57, p=0.11), respectively, non-significant correlations to the change in VO2max at the end of the conditioning program (∆VO2max). Significant and near-perfect correlation was found between the change in the weekly mean lnRMSSD values from weeks 1 and 3 (∆lnRMSSDM) and ∆VO2max (r=0.90, p=0.002). The current results have identified that the initial change in weekly mean lnRMSSD from weeks 1 to 3 of a conditioning protocol was strongly associated with the eventual adaptation of VO2max.

Interpreting daily heart rate variability changes in collegiate female soccer players.

Heart rate variability (HRV) is an objective physiological marker that may be useful for monitoring training status in athletes. However, research aiming to interpret daily HRV changes in female athletes is limited. The objectives of this study were: 1) to assess daily HRV (i.e., log-transformed root mean square of successive R-R interval differences, lnRMSSD) trends both as a team and intra-individually in response to varying training load (TL); and 2) to determine relationships between lnRMSSD fluctuation (coefficient of variation, lnRMSSDcv) and psychometric and fitness parameters in collegiate female soccer players (N.=10). Ultra-short, Smartphone-derived lnRMSSD and psychometrics were evaluated daily throughout 2 consecutive weeks of high and low TL. After the training period, fitness parameters were assessed. When compared to baseline, reductions in lnRMSSD ranged from unclear to very likely moderate during the high TL week (effect size ±90% confidence limits [ES±90% CL] =-0.21±0.74 to -0.64±0.78, respectively) while lnRMSSD reductions were unclear during the low TL week (ES±90% CL=-0.03±0.73 to -0.35±0.75, respectively). A large difference in TL between weeks was observed (ES±90% CL=1.37±0.80). Higher lnRMSSDcv was associated with greater perceived fatigue and lower fitness (r [upper and lower 90% CL]=-0.55 [-0.84, -0.003] large, -0.65 [-0.89, -0.15] large). Athletes with lower fitness or higher perceived fatigue demonstrated greater reductions in lnRMSSD throughout training. This information can be useful when interpreting individual lnRMSSD responses throughout training for managing player fatigue.

Evaluating Individual Training Adaptation With Smartphone-Derived Heart Rate Variability in a Collegiate Female Soccer Team.

Monitoring individual responses throughout training may provide insight to coaches regarding how athletes are coping to the current program. It is unclear if the evolution of heart rate variability (HRV) throughout training in team-sport athletes can be useful in providing early indications of individual adaptation. This study evaluated relationships between changes in resting cardiac autonomic markers derived from a novel smartphone device within the first 3 weeks of a 5-week conditioning program and the eventual change in intermittent running performance at week 5 among 12 collegiate female soccer players. Change variables from weeks 1 to 3 of the weekly mean and weekly coefficient of variation for resting heart rate ([INCREMENT]RHRmean and [INCREMENT]RHRcv, respectively) and log-transformed root mean square of successive R-R intervals multiplied by 20 ([INCREMENT]Ln rMSSDmean and [INCREMENT]Ln rMSSDcv, respectively) were compared with changes in Yo-Yo Intermittent Recovery Test Level 1 performance ([INCREMENT]Yo-Yo). A very large and significant correlation was found between [INCREMENT]Yo-Yo and [INCREMENT]Ln rMSSDcv (r = -0.74; p = <0.01) and a large nonsignificant correlation was found with [INCREMENT]Ln rMSSDmean (r = 0.50; p = 0.096). This study suggests that a decrease in Ln rMSSDcv within the first 3 weeks of training is a favorable response, indicative of positive adaptation. Collecting daily HRV data with a smartphone application using ultrashort HRV measures seems useful for athlete monitoring.

Smartphone-Derived Heart-Rate Variability and Training Load in a Women's Soccer Team.

This study evaluated the 7-d mean and coefficient of variation (CV) of supine and standing ultrashort log-transformed root mean square of successive R-R intervals multiplied by 20 (lnRMSSDx20) obtained with a smartphone application (app) in response to varying weekly training load (TL). In addition, the authors aimed to determine if these values could be accurately assessed in as few as 5 or 3 d/wk. Nine women from a college soccer team performed daily heart-rate-variability measures with an app in supine and standing positions over 3 wk of moderate, high, and low TL. The mean and CV over 7, 5, and 3 d were compared within and between weeks. The 5- and 3-d measures within each week provided very good to nearly perfect intraclass correlations (ICCs .74-.99) with typical errors ranging from 0.64 to 5.65 when compared with the 7-d criteria. The 7, 5, and 3-d supine CV and the 7-day standing CV were moderately lower during the low-load than the high-load week (P .003-.045, effect sizes 0.86-0.92), with no significant changes occurring in the other measures. This study supports the use of the mean and CV of lnRMSSD measured across at least 5 d for reflecting weekly values. The supine lnRMSSDx20 CV as measured across 7, 5, and 3 d was the most sensitive marker to the changes in TL in the 3-wk period.

Validation of semi-analytical inversion models for inherent optical properties from ocean color in coastal Yellow Sea and East China Sea

The performances of three semi-analytical retrieval models for water inherent optical properties were validated in the coastal Yellow Sea and East China Sea, including the Quasi-Analytical Algorithm (QAA), the Garver-Siegel-Maritorena model (GSM) and the Over Constrained Linear Matrix (LM). The model-retrieved parameters, namely absorption coefficients of phytoplankton (a ph), colored dissolved and detrital particulate matter (a dg), total absorption coefficients (a t), and backscattering coefficient of particles (b bp), were compared. The bio-optical datasets collected from a Yellow Sea and East China Sea cruise in April and September 2003 were used in the study. The QAA model performed the best in retrieval for all the coefficients, showing log-transformed root mean square errors of 0.306 for a ph, 0.268 for a dg, 0.144 for a t, and 0.273 for b bp at 443 nm. The LM model showed a slightly larger deviation than the QAA model with a similar error trend for absorption coefficients, but it returned the largest uncertainties for b bp, with log-transformed root mean square error up to 0.646. The GSM model, however, yielded the largest and fluctuating errors along with wavelength for absorption coefficient retrievals. Substituting the fitting parameters from measured data for the empirical spectral parameters, all three models returned better results. These improvements demonstrated that semi-analytical algorithms designed for ocean water need regional modifications before applying to coastal areas. The QAA algorithm may be the most suitable model for retrieval for the Yellow Sea and East China Sea, and future model refinements should concentrate on regional modeling of inherent optical properties.