Body composition estimates using a 2D image analysis system across different environmental conditions: An agreement study.

PURPOSE: This study examined the agreement between %Fat measurements using a smartphone-based application (IMAGE) across different environmental conditions. METHODS: A single reference image was obtained using an 8 MP smartphone camera under Ambient Light in front of a white background. Additional photos were obtained using a 0.7 MP, 5 MP, and 12 MP smartphone cameras; low-, moderate-, and bright-lighting conditions; and various color backgrounds including black, green, orange, and gray. RESULTS: %Fat measured using the 0.7 MP camera (27.8 ± 6.2 %Fat) was higher than the reference (26.8 ± 6.1 %Fat) (p < 0.001). The black (32.0 ± 12.0 %Fat), green (27.5 ± 6.3 %Fat), and gray (27.8 ± 6.3 %Fat) backgrounds yielded higher %Fat than the white (p = 0.03, 0.01, and 0.001). All camera, lighting, and background conditions were strongly correlated with the reference (all intraclass correlation coefficient [ICC] >0.98, all standard error of the estimate [SEE] <1.5 %Fat, all p < 0.001), except the black background which yielded poorer agreement with the white background (ICC = 0.69, SEE = 4.5%, p < 0.001). CONCLUSION: %Fat from IMAGE were strongly correlated across various environmental conditions.

Deuterium oxide validation of bioimpedance total body water estimates in Hispanic adults.

Background: To date, body composition assessments in Hispanics, computed via bioimpedance devices, have primarily focused on body fat percent, fat mass, and fat-free mass instead of total body water (TBW). Additionally, virtually no information is available on which type of bioimpedance device is preferred for TBW assessments in Hispanic populations. Purpose: The purpose of this study was to validate two bioimpedance devices for the estimate of TBW in Hispanics adults when using a criterion deuterium oxide (D2O) technique. Methods: One-hundred thirty individuals (males: n = 70; females: n = 60) of Hispanic descent had TBW estimated via D2O, single-frequency bioimpedance analysis ([SF-BIA] Quantum V, RJL Systems) and bioimpedance spectroscopy ([BIS] SFB7 Impedimed). Results: The mean values for SF-BIA were significantly lower than D2O when evaluating the entire sample (37.4 L and 38.2 L, respectively; p < 0.05). In contrast, TBW values were not statistically significant when comparing D2O against BIS (38.4 L, p > 0.05). Bland-Altman analysis indicated no proportional bias when evaluating the entire sample for SF-BIA or BIS. The standard error of estimate and total error values were ≤ 2.3 L and Lin's concordance correlation coefficient were ≥ 0.96 for all comparisons. Conclusion: The SF-BIA and BIS devices evaluated in the current study hold promise for accurate estimation of TBW in Hispanic adults. While both methods demonstrated relatively low errors relative to the D2O criterion, BIS exhibited a more consistent performance, particularly at the group level. These findings provide essential information for researchers and clinical nutrition practitioners assessing TBW in Hispanic adults.

Disparities in physical activity between sexual minority and heterosexual women: A systematic review and meta-analysis.

Research examining potential differences in physical activity (PA) between sexual minority women (SMW) and heterosexual women have yielded inconsistent results. OBJECTIVE: Therefore, the purpose of this systematic review and meta-analysis is to examine potential differences in PA between SMW and heterosexual women and to identify potential moderators that may partially explain observed differences in PA. METHODS: All studies were peer reviewed, published in English, and included a continuous measure of PA for SMW and heterosexual women. A standardized mean difference effect size (ES) was used to compare groups, with random effects models used to estimate a mean ES and 95% CI using a 3-level meta-analysis model to adjust for the correlation between effects nested within studies. RESULTS: The cumulative results of 24 effects gathered from 7 studies indicated there was no difference in PA between SMW (n = 1619) and heterosexual women (n = 103,295) (ES = -0.038, 95%CI -0.179 to 0.102, p = 0.576). Despite no mean differences, moderate-high heterogeneity was observed, indicating that the results were not consistent across effects (I2 = 64.8%, Q23 = 36.7, p = 0.035). The difference in PA was associated with age (ß = -0.018, 95%CI -0.034 to -0.003, p = 0.022) and BMI (ß = -0.145, 95%CI -0.228 to -0.061, p = 0.002), with a quadratic relationship observed for both variables. CONCLUSIONS: Although the results of the current analysis did not indicate significant differences in PA behaviors between SMW and heterosexual women, age and BMI modify the association and are curvilinear in nature; such that smaller differences in PA were observed between SMW and heterosexual women when samples were middle-aged and overweight.

Evaluation of Skinfold Techniques in People with Down Syndrome: Development of a New Equation.

The primary aim of this study was to evaluate the accuracy of skinfold thickness (SFT) measurements for the estimation of %Fat when compared to dual energy X-ray absorptiometry (DXA) in individuals with Down syndrome (DS). The secondary aim was to develop a new SFT-based body fat equation (SFTNICKERSON). SFT-based %Fat was estimated using a body fat equation from González-Agüero (SFTG-A) and body density conversion formulas from Siri (SFTSIRI) and Brozek (SFTBROZEK). Criterion %Fat was measured via DXA. SFTG-A, SFTSIRI, and SFTBROZEK were significantly lower than DXA (mean differences ranged from -7.59 to -13.51%; all p < 0.001). The SEE values ranged from 3.47% (SFTBROZEK) to 8.60% (SFTG-A). The 95% limits of agreement were greater than ±10% for all comparisons. Mid-axilla and suprailium were significant predictors of %Fat (both p < 0.05). %Fat SFTNICKERSON = 10.323 + (0.661 × mid-axilla) + (0.712 × suprailium). Age and all other skinfold sites were not statically significant in the regression model (all p > 0.05). Current findings indicate that SFTG-A, SFTSIRI, and SFTBROZEK erroneously place an individual with excessive adiposity in a normal healthy range. Accordingly, the current study developed a new equation (SFTNICKERSON) that can easily be administered in people with DS in a quick and efficient time frame. However, further research is warranted in this area.

Agreement between ultrasound protocols for the estimation of body fat percentage: Comparison to a four-compartment model.

The purpose of this study was to examine the agreement between body fat percentage (%Fat) estimates derived from a standardized ultrasound protocol (%FatIASMS ), a commonly used skinfold (SKF)-site-based ultrasound protocol (%FatJP ), and a criterion four-compartment (4C) model (%Fat4C ). For the ultrasound protocols, all measurement sites were marked, measured and analyzed by the same evaluator. Subcutaneous adipose tissue (SAT) thickness was measured manually at the region where the muscle fascia was parallel to the skin and the average value per measurement site was used to calculate body density and subsequently %Fat. A repeated-measures analysis of variance with a priori planned contrasts was used to compare %Fat values between the 4C criterion and both ultrasound methods. Small nonsignificant mean differences were observed between %FatIASMS (18.82 ± 14.21%Fat, effect size [ES] = 0.25, p = 0.178), %FatJP (18.23 ± 13.32%Fat, ES = 0.32, p = 0.050) and the %Fat4C criterion (21.70 ± 7.57%Fat); however, %FatIASMS did not yield a smaller mean difference than the %FatJP (p = 0.287). Additionally, %FatIASMS (r = 0.90, p < 0.001, standard error of the estimate [SEE] = 3.29%) and %FatJP (r = 0.88, p < 0.001, SEE = 3.60%) were strongly correlated with the 4C criterion, however, %FatIASMS did not yield better agreement than %FatJP (p = 0.257). Despite slightly underestimating %Fat, both ultrasound techniques demonstrated Good-Very Good agreement with the 4C criterion, with comparable mean differences, correlations, and SEE. The International Association of Sciences in Medicine and Sports (IASMS) standardized protocol using manual calculations of SAT was comparable to the SKF-site-based ultrasound protocol when compared to the 4C criterion. These results indicate that the IASMS (with manually measured SAT) and SKF-site-based ultrasound protocols may be of practical use to clinicians.

Acute Blood Flow Responses to Varying Blood Flow Restriction Pressures in the Lower Limb.

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.

Repeated cold-water immersion improves autonomic cardiac modulation following five sessions of high-intensity interval exercise.

PURPOSE: The study aimed to investigate the effect of repeated cold-water immersion (CWI) after high-intensity interval exercise sessions on cardiac-autonomic modulation, neuromuscular performance, muscle damage markers, and session internal load. METHODS: Twenty-one participants underwent five sessions of high-intensity interval exercise (6-7 bouts of 2 min; pause of 2 min) over a two-week period. Participants were allocated randomly into either a group that underwent CWI (11-min; 11 °C) or a group that performed passive recovery after each exercise session. Before the exercise sessions were performed, countermovement jump (CMJ) and heart rate variability were recorded (i.e., rMSSD, low and high frequency power and its ratio, SD1 and SD2). Exercise heart rate was calculated by recording the area under the curve (AUC) response. Internal session load was evaluated 30 min after each session. Blood concentrations of creatine kinase and lactate dehydrogenase were analyzed before the first visit and 24 h after the last sessions. RESULTS: The CWI group presented higher rMSSD than the control group at each time point (group-effect P = 0.037). The SD1 was higher in CWI group when compared to the control group following the last exercise session (interaction P = 0.038). SD2 was higher in CWI group compared to the control group at each time point (group-effect P = 0.030). Both groups presented equal CMJ performance (P > 0.05), internal load (group-effect P = 0.702; interaction P = 0.062), heart rate AUC (group-effect P = 0.169; interaction P = 0.663), and creatine kinase and lactate dehydrogenase blood concentrations (P > 0.05). CONCLUSION: Repeated post-exercise CWI improves cardiac-autonomic modulation. However, no differences in neuromuscular performance, muscle damage markers, or session internal load were demonstrated between the groups.

Acute Responses to High-Intensity Back Squats with Bilateral Blood Flow Restriction.

This study examined the acute effects of high-intensity resistance exercise with blood flow restriction (BFR) on performance and fatigue, metabolic stress, and markers of inflammation (interleukin-6 (IL-6)), muscle damage (myoglobin), angiogenesis (vascular endothelial growth factor (VEGF)). Thirteen resistance-trained participants (four female, 24.8 ± 4.7 years) performed four sets of barbell back-squats (75% 1RM) to failure under two conditions: blood flow restriction (BFR, bilateral 80% occlusion pressure) and control (CTRL). Completed repetitions and pre-post-exercise changes in maximal voluntary isometric contractions, countermovement jump, barbell mean propulsive velocity, and surface electromyography were recorded. Pre-post blood lactate (BLa) and venous blood samples for analysis of IL-6, myoglobin, and VEGF were collected. Ratings of perceived exertion (RPE) and pain were recorded for each set. Fewer repetitions were performed during BFR (25.5 ± 9.6 reps) compared to CTRL (43.4 ± 14.2 reps, p < 0.001), with greater repetitions performed during sets 1, 2, and 4 (p < 0.05) in CTRL. Although RPE between conditions was similar across all sets (p > 0.05), pain was greater in BFR across all sets (p < 0.05). Post-exercise fatigue was comparable between conditions. BLa was significantly greater in CTRL compared to BFR at two minutes (p = 0.001) but not four minutes post-exercise (p = 0.063). IL-6 was significantly elevated following BFR (p = 0.011). Comparable increases in myoglobin (p > 0.05) and no changes in VEGF were observed (p > 0.05). BFR increases the rate of muscular fatigue during high-intensity resistance exercise and acutely enhances IL-6 response, with significantly less total work performed, but increases pain perception, limiting implementation.

Dual energy X-ray absorptiometry produces larger measurement error in non-Hispanic Caucasians than Hispanics.

BACKGROUND: Dual energy X-ray absorptiometry (DXA) is often used as a criterion measure in body composition research and in clinical settings for the estimate of body fat percent (%Fat). The accuracy of DXA for predicting %Fat has primarily been conducted in non-Hispanic populations. AIM: The purpose of this study was to determine the agreement of DXA-derived %Fat in Hispanic and non-Hispanic Caucasian adults. METHODS: The sample consisted of Hispanic males (n = 96) and females (n = 102) and non-Hispanic Caucasian males (n = 145) and females (n = 161). The %Fat of a whole-body DXA scan was compared against a criterion 4-compartment (4C) model via constant error (CE = DXA - 4C model) and 95% limits of agreement. Also, a 2 × 2 factorial ANOVA, using CE as a dependent variable, was conducted to examine the main and interaction effects of sex and ethnicity. RESULTS: When compared to the 4C model, DXA overestimated %Fat by 4.0% in Hispanics and 5.5% in non-Hispanic Caucasians (all p < 0.05). The 95% limits of agreement ranged from ±5.5% to ±5.9% for all group comparisons. The 2 × 2 factorial ANOVA indicated the CE was greater in non-Hispanic Caucasians than Hispanics (CE difference = 1.5%; p < 0.05). CONCLUSION: Our findings revealed that DXA significantly overestimates %Fat in both populations (Hispanics and non-Hispanic Caucasians), when compared to a 4C model, regardless of sex (male or female). However, the error is more profound in non-Hispanic Caucasian adults. It is worth nothing that DXA may be useful for tracking changes in body composition that occur throughout a lifestyle intervention. Nonetheless, practitioners should be aware that the estimate of %Fat from DXA may be larger than the actual values obtained from a 4C model.

Hemodynamic Responses to Resistance Exercise with Blood Flow Restriction Using a Practical Method Versus a Traditional Cuff-Inflation System.

The aim of this study was to examine the potential differences in acute hemodynamic responses and muscular performance outcomes following resistance exercise between traditional blood flow restriction (TRABFR) and a novel band tissue flossing method (BTFBFR). METHODS: Fifteen healthy young adults (23.27 ± 2.69 years) visited the lab for three sessions (≥72 h apart). Each session's exercise consisted of three sets of 20 maximum-effort seated leg extensions and flexions with one of three conditions: control (CON), TRABFR (50% limb occlusion pressure (LOP)), or BTFBFR. During TRABFR and BTFBFR sessions, occlusion was applied immediately prior to exercise and removed immediately after. Heart rate was collected prior to exercise, after onset of occlusion, immediately after exercise, and one-minute after removal of occlusion. Ultrasonography was performed prior to, and at least 30 s after, occlusion. RESULTS: BTFBFR caused greater reductions in arterial distance (14.28%, p = 0.010) and arterial area (28.43%, p = 0.020) than TRABFR. BTFBFR was able to significantly reduce arterial flow below pre-occlusion values, while TRABFR did not. Both conditions caused significant elevations in heart rate following occlusion (TRABFR: +4.67 bpm, p = 0.046 and BTFBFR: +6.07 bpm, p = 0.034), immediately post-exercise (TRABFR: +56.93 bpm, p < 0.001 and BTFBFR: +52.79 bpm, p < 0.001) and one-minute post-exercise (TRABFR: +15.71, p = 0.003 and BTFBFR: +14.57, p < 0.001). Only BTFBFR caused significant reductions in performance as measured by average power per repetition. CONCLUSIONS: BTFBFR causes a more exaggerated decrease in arterial blood flow as well as muscular power when compared to traditional TRABFR at 50% of LOP.

Effect of Competitive Status and Experience on Heart Rate Variability Profiles in Collegiate Sprint-Swimmers.

ABSTRACT: 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.

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 Validity of Perceived Recovery Status as a Marker of Daily Recovery Following a High-Volume Back-Squat Protocol.

Although a variety of tools to monitor recovery have been developed, many are impractical for daily use due to cost, time, and challenges with interpretation. The Perceived Recovery Status (PRS) scale was recently developed as an expeditious, noninvasive tool to assess recovery status. While PRS has been strongly associated with repeated sprinting performance, a paucity of research exists relating PRS and performance recovery following resistance exercise. PURPOSE: The purpose of this study was to evaluate the sensitivity of PRS as a subjective marker of recovery up to 72 hours after a high-volume back-squat protocol. METHODS: Eleven resistance-trained men reported to the laboratory on 5 separate occasions (1 familiarization session and 4 testing sessions). The first testing session was considered the baseline session and consisted of a nonfatiguing performance assessment (ie, countermovement jumps and back squats) and a fatiguing back-squat protocol of 8 sets of 10 at 70% 1-repetition maximum separated by 2 minutes of recovery. Participants returned 24, 48, and 72 hours following baseline to provide a PRS rating and complete the performance assessment. RESULTS: Repeated-measures correlations revealed strong associations between PRS countermovement jump (r = .84) and mean bar velocity (r = .80) (both P < .001). CONCLUSIONS: The current findings suggest that PRS can be used as a method to effectively assess daily recovery following a fatiguing bout of resistance exercise. Practitioners are cautioned that the relationship between PRS and performance recovery is individualized, and equivalent PRS scores between individuals are not indicative of similar recovery.

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

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

Validity of a 3-compartment body composition model using body volume derived from a novel 2-dimensional image analysis program.

BACKGROUND/OBJECTIVES: The purpose of this study was: (1) to compare body volume (BV) estimated from a 2-dimensional (2D) image analysis program (BVIMAGE), and a dual-energy x-ray absorptiometry (DXA) equation (BVDXA-Smith-Ryan) to an underwater weighing (UWW) criterion (BVUWW); (2) to compare relative adiposity (%Fat) derived from a 3-compartment (3C) model using BVIMAGE (%Fat3C-IMAGE), and a 4-compartment (4C) model using BVDXA-Smith-Ryan (%Fat4C-DXA-Smith-Ryan) to a 4C criterion model using BVUWW (%Fat4C-UWW). SUBJECT/METHODS: Forty-eight participants were included (60% male, 22.9 ± 5.0 years, 24.2 ± 2.6 kg/m2). BVIMAGE was derived using a single digital image of each participant taken from the rear/posterior view. DXA-derived BV was calculated according to Smith-Ryan et al. Bioimpedance spectroscopy and DXA were used to measure total body water and bone mineral content, respectively, in the 3C and 4C models. A standardized mean effect size (ES) assessed the magnitude of differences between models with values of 0.2, 0.5, and 0.8 for small, moderate, and large differences, respectively. Data are presented as mean ± standard deviation. RESULTS: Near-perfect correlation (r = 0.998, p < 0.001) and no mean differences (p = 0.267) were observed between BVIMAGE (69.6 ± 11.5 L) and BVUWW (69.5 ± 11.4 L). No mean differences were observed between %Fat4C-DXA-Smith-Ryan and the %Fat4C-UWW criterion (p = 0.988). Small mean differences were observed between %Fat3C-IMAGE and %Fat4C-UWW (ES = 0.2, p < 0.001). %Fat3C-IMAGE exhibited smaller SEE and TE, and tighter limits of agreement than %Fat4C-DXA-Smith-Ryan. CONCLUSIONS: The 2D image analysis program provided an accurate and non-invasive estimate of BV, and subsequently %Fat within a 3C model in generally healthy, young adults.

Vagally Derived Heart Rate Variability and Training Perturbations With Menses in Female Collegiate Rowers.

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.

Agreement Between A 2-Dimensional Digital Image-Based 3-Compartment Body Composition Model and Dual Energy X-Ray Absorptiometry for The Estimation of Relative Adiposity.

The purpose of this study was to compare relative adiposity (%Fat) derived from a 2-dimensional image-based 3-component (3C) model (%Fat3C-IMAGE) and dual-energy X-ray absorptiometry (DXA) (%FatDXA) against a 5-component (5C) laboratory criterion (%Fat5C). 57 participants were included (63.2% male, 84.2% White/Caucasian, 22.5±4.7 yrs., 23.9±2.8 kg/m2). For each participant, body mass and standing height were measured to the nearest 0.1 kg and 0.1 cm, respectively. A digital image of each participant was taken using a 9.7 inch, 16g iPad Air 2 and analyzed using a commercially available application (version 1.1.2, made Health and Fitness, USA) for the estimation of body volume (BV) and inclusion in %Fat3C-IMAGE . %Fat3C-IMAGE and %Fat5C included measures of total body water derived from bioimpedance spectroscopy. The criterion %Fat5C included BV estimates derived from underwater weighing and bone mineral content measures via DXA. %FatDXA estimates were calculated from a whole-body DXA scan. A standardized mean effect size (ES) assessed the magnitude of differences between models with values of 0.2, 0.5, and 0.8 for small, moderate, and large differences, respectively. Data are presented as mean ± standard deviation. A strong correlation (r = 0.94, p <.001) and small mean difference (ES = 0.24, p <.001) was observed between %Fat3C-IMAGE (19.20±5.80) and %Fat5C (17.69±6.20) whereas a strong correlation (r = 0.87, p <.001) and moderate-large mean difference (ES = 0.70, p <.001) was observed between %FatDXA (22.01±6.81) and %Fat5C. Furthermore, %Fat3C-IMAGE (SEE = 2.20 %Fat, TE= 2.6) exhibited smaller SEE and TE than %FatDXA (SEE = 3.14 %Fat, TE = 5.5). The 3C image-based model performed slightly better in our sample of young adults than the DXA 3C model. Thus, the 2D image analysis program provides an accurate and non-invasive estimate of %Fat within a 3C model in young adults. Compared to DXA, the 3C image-based model allows for a more cost-effective and portable method of body composition assessment, potentially increasing accessibility to multi-component methods.

Comparison of Heart Rate Variability Responses to Varying Resistance Exercise Volume-Loads.

Purpose: The aim of this study was to compare the effects of low ([LV]; 4 total sets), moderate ([MV]; 8 total sets), and high set volumes ([HV]; 12 total sets) in acute full-body resistance exercise sessions on post-exercise parasympathetic reactivation measured using RMSSD. Methods: Ten resistance-trained participants (25.8 ± 6.8 yr., 173.4 ± 10.6 cm, 75.4 ± 9.9 kg) performed three resistance exercise sessions. During each session, heart rate variability (HRV) was measured pre- and for 30 min post-exercise, divided into 5-min segments stabilization, Post5-10, Post10-15, Post15-20, Post20-25, and Post25-30. Repeated-measures ANOVA was used to assess differences within and between pre-post exercise natural logarithm RMSSD (LnRMSSD) values. To assess the initial change in LnRMSSD, the delta percent change (ΔLnRMSSD) from pre-exercise to Post5-10 (ΔLnRMSSDpre-post) was calculated for each session. The ΔLnRMSSD was also calculated between Post5-10 and Post25-30 (ΔLnRMSSDpost5-30) to assess recovery. Results: Significant differences were observed between sessions and when comparing pre-exercise values to all post-exercise times across sessions (p ≤ .05). The LV session resulted in significantly higher mean LnRMSSD value (3.62) post-exercise compared to both the MV (3.11, effect size [ES] =  3.77) and HV (3.02, ES =  3.92) sessions while the MV and HV sessions produced similar responses. Across sessions no return to baseline occurred and when comparing sessions, no significant differences were found in ΔLnRMSSDpre-post or ΔLnRMSSDpost5-30. Conclusion: Acute bouts of full-body resistance exercise can cause similar reductions in LnRMSSD from pre-exercise levels and can delay parasympathetic reactivation back to baseline values during the same 30-min recovery period despite differences in set volume.

Generalized Equations for Predicting Percent Body Fat from Anthropometric Measures Using a Criterion Five-Compartment Model.

INTRODUCTION: Anthropometric-based equations are used to estimate percent body fat (%BF) when laboratory methods are impractical or not available. However, because these equations are often derived from two-compartment models, they are prone to error because of the assumptions regarding fat-free mass composition. The purpose of this study was to develop a new anthropometric-based equation for the prediction of %BF, using a five-compartment (5C) model as the criterion measure. METHODS: A sample of healthy adults (52.2% female; age, 18 to 69 yr; body mass index, 15.7 to 49.5 kg·m-2) completed hydrostatic weighing, dual-energy x-ray absorptiometry, and bioimpedance spectroscopy measurements for calculation of 5C %BF (%BF5C), as well as skinfolds and circumferences. %BF5C was regressed on anthropometric measures using hierarchical variable selection in a random sample of subjects (n = 279). The resulting equation was cross-validated in the remaining participants (n = 78). New model performance was also compared with several common anthropometric-based equations. RESULTS: The new equation [%BFNew = 6.083 + (0.143 × SSnew) - (12.058 × sex) - (0.150 × age) - (0.233 × body mass index) + (0.256 × waist) + (0.162 × sex × age)] explained a significant proportion of variance in %BF5C (R2 = 0.775, SEE = 4.0%). Predictors included sum of skinfolds (SSnew, midaxillary, triceps, and thigh) and waist circumference. The new equation cross-validated well against %BF5C when compared with other existing equations, producing a large intraclass correlation coefficient (0.90), small mean bias and limits of agreement (0.4% ± 8.6%), and small measures of error (SEE = 2.5%). CONCLUSIONS: %BFNew improved on previous anthropometric-based equations, providing better overall agreement and less error in %BF estimation. The equation described in this study may provide an accurate estimate of %BF5C in healthy adults when measurement is not practical.

Prediction of underwater residual lung volume in healthy men and women.

Regression equations are commonly used to predict residual lung volume (RV) during underwater weighing when measurement is not practical. However, the equations currently available were derived from on-land measures of RV and may account for changes in lung capacity during submersion, thus leading to inaccuracies in assessment of percent body fat (%BF). The purpose of this study was to (1) develop a new equation (RVNEW ) for the prediction of underwater RV, (2) cross-validate RVNEW and compare it to existing RV equations, and (3) compare the effects of RVNEW and existing equations on underwater %BF. One-hundred seventy-five healthy adults were recruited to complete simultaneous hydrostatic weighing and RV measurements. The sample was randomly divided into development (n = 131) and cross-validation (n = 44) cohorts. Regression analysis in the development cohort resulted in the following equation: underwater RV = -3·419 + 0·026 × height (cm) + 0·019 × age (y) (p < 0·001; R2  = 0·53; SEE = 0·26). In the cross-validation cohort, Bland-Altman analysis revealed that the new equation provided the best overall agreement with underwater RV (bias ± 1·96 SD, 0·07 ± 0·5 L), while existing equations produced significantly different values from measured RV and wider limits of agreement. When used to calculate %BF, the new RV equation produced the strongest agreement with underwater %BF (-0·5% ± 3·8%), although all equations produced strong correlations (all r > 0·95) and limits of agreement ≤4·7%. The results of this study suggest that RVNEW may be more appropriate for RV estimation during hydrostatic weighing than existing equations. However, its applicability to populations outside the current study needs to be examined.