Validity of Using the Load-Velocity Relationship to Estimate 1 Repetition Maximum in the Back Squat Exercise: A Systematic Review and Meta-Analysis.

ABSTRACT: LeMense, AT, Malone, GT, Kinderman, MA, Fedewa, MV, and Winchester, LJ. Validity of using the load-velocity relationship to estimate 1 repetition maximum in the back squat exercise: a systematic review and meta-analysis. J Strength Cond Res 38(3): 612-619, 2024-The one repetition maximum (1RM) test is commonly used to assess muscular strength. However, 1RM testing can be time consuming, physically taxing, and may be difficult to perform in athletics team settings with practice and competition schedules. Alternatively, 1RM can be estimated from bar or movement velocity at submaximal loads using the minimum velocity threshold (MVT) method based on the load-velocity relationship. Despite its potential utility, this method's validity has yielded inconsistent results. The purpose of this systematic review and meta-analysis was to assess the validity of estimated 1RM from bar velocity in the back squat exercise. A systematic search of 3 electronic databases was conducted using combinations of the following keywords: "velocity-based training," "load-velocity profiling," "mean velocity," "mean propulsive velocity," "peak velocity," "maximal strength," "1RM," "estimation," "prediction," "back squat," and "regression." The search identified 372 unique articles, with 4 studies included in the final analysis. Significance was defined as a p level less than 0.05. A total of 27 effects from 71 subjects between the ages of 17-25 years were analyzed; 85.2% of effects were obtained from male subjects. Measured 1RMs ranged from 86.5 to 153.1 kg, whereas estimated 1RMs ranged from 88.6 to 171.6 kg. Using a 3-level random effects model, 1RM back squat was overestimated when derived from bar velocity using the MVT method (effect sizes [ES] = 0.5304, 95% CI: 0.1878-0.8730, p = 0.0038). The MVT method is not a viable option for estimating 1RM in the free weight back squat. Strength and conditioning professionals should exercise caution when estimating 1RM from the load-velocity relationship.

Lower limb blood flow occlusion increases systemic pressor response without increasing brachial arterial blood flow redistribution in women.

This study was conducted to investigate the systemic hemodynamic and vascular changes in women during and after two commonly used clinical blood flow restriction (BFR) pressures at rest. There are minimal data regarding the independent effects of BFR on hemodynamic and systemic vascular changes due to pressor response, particularly among women. Therefore, this study investigated BFR-induced alterations in pressor response and systemic flow redistribution at rest during two commonly used pressures (50% and 80% limb occlusion pressure [LOP]). Fifteen women (22.1 ± 4.2 years) completed two randomised sessions involving 8-min of bilateral, lower limb restriction at 50% or 80% LOP followed by 8-min of recovery post-deflation. Changes in vascular (arterial diameter [DIA], time-averaged mean velocity [TAMV], volume flow [VF], and area) and hemodynamic (heart rate [HR] and blood pressure) measures over time (pre-, during, post-occlusion) and by session (50% vs. 80% LOP) were tested using repeated measures analysis of variance. Repeated measures correlations (rrm) quantified common intraindividual associations between BFR-induced hemodynamic and vascular responses. HR increased from baseline during 50% LOP and remained elevated during recovery (p < 0.05). HR increased from baseline during 80% LOP, while tibial VF and TAMV decreased (p < 0.03 for all). HR and TAMV values returned to baseline during recovery, while brachial artery VF decreased (p < 0.05). Changes in HR, brachial VF, and brachial TAMV were similar between 50% and 80% LOP (rrm = 0.32-0.70, p < 0.05 for all). At 80% LOP, changes in HR were positively correlated with brachial VF (rrm = 0.38) and TAMV (rrm = 0.43) and negatively correlated with tibial VF (rrm = -0.36) and TAMV (rrm = -0.30) (p < 0.05 for all). Results suggest that BFR at 80% LOP elicits an acute systemic pressor reflex without concomitant increases in brachial arterial flow, while 50% LOP elicits a subdued response.

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.

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.

Cardiovascular Responses During Light-intensity Aerobic Exercise with Varying Levels of Limb Occlusion Pressures.

The study aimed to assess cardiovascular responses to low-intensity aerobic exercise with varying levels of limb occlusion pressures (LOP) in a healthy population of men and women 30 to 60 years. The study was a single-session repeated measures design. Thirty individuals completed the study. All subjects participated in a single bout of low-intensity cycling (30-39% HRR) with bilateral lower extremity (LE) BFR for four 5-minute stages [0% (No BFR), 40%, 60%, and 80% LOP] with a 2-minute active rest between stages (BFR pressure released). The subjects' systolic blood pressure (SBP), diastolic blood pressure (DBP), mean arterial pressure (MAP), heart rate (HR), oxygen saturation (SpO2), and ratings of perceived exertion (RPE) were measured at rest, peak, immediately post, post-15 minutes, and post-30 minutes. Peak SBP (no BFR 160.7 ±19.1 mmHg; 40% LOP 173.6 ± 18.7 mmHg; 60 % LOP; 182.5 ± 21.1 mmHg; 80% LOP 193.5± 23.3 mmHg ; p<0.001; ηP2=.747), DBP (no BFR 74.9 ± 8.5 mmHg; 40% LOP (83.0 ± 9.0 mmHg;60 % LOP 90.4 ± 8.7 mmHg; 80% LOP 97.7 ± 9.5 mmHg ;p<0.001; ηP2=.924), MAP (no BFR 103.5 ± 10.1 mmHg; 40% LOP 113.2 ± 10.5 mmHg; 60% LOP 121.1 ± 11.7 mmHg; 80% LOP 129.7 ± 12.9 mmHg; p<0.001; ηP2=.960), and RPE (No BFR 10.0 ± 2.0; 40 % LOP 11.5 ± 2.3; 60% LOP 13.2 ± 2.6; 80% LOP 14.5 ± 3.; p<0.001; ηP2=.826) were significantly higher with each progressing stage. The results indicate that low-intensity cycling with bilateral LE BFR for each LOP stage resulted in elevated SBP, DBP, MAP, and RPE despite maintaining a fixed HR.

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.

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.

Ease of restroom access influences fluid consumption habits and health in classroom teachers.

Objectives. There are rising concerns about the health of classroom teachers in the USA, including stress, hypertension and frequent urinary tract infections. Teacher working conditions are likely a contributor to their health concerns. Many teachers report that they cannot easily take a restroom break at work, and therefore they consume minimal water or other fluids. This study investigated the relationship between restroom access and fluid consumption and the prevalence of renal and cardiovascular health complications in classroom teachers. Methods. The responses of 844 teachers (92% women, 8% men; 65.1% between age 26 and 45 years) to an online survey about restroom accessibility, fluid consumption and health were analyzed using descriptive statistics, χ2 analyses and logistic regression. Results. Fifty-nine percent of teachers could not easily take a restroom break, and 54.7% consumed fewer than 2 cups of water per workday. Furthermore, 44.8% reported being pre-hypertensive and 4.9% reported being hypertensive. Teachers with insufficient restroom access were significantly more likely to report frequent urinary tract infections. Conclusions. This study demonstrates a relationship between restroom access, fluid consumption and renal/cardiovascular health in classroom teachers. Future research should directly investigate how teacher work environment impacts renal and cardiovascular health.

African American Females Are Less Metabolically Flexible Compared with Caucasian American Females following a Single High-Fat Meal: A Pilot Study.

The relationship between metabolic flexibility (MF) and components of metabolic disease has not been well-studied among African American (AA) females and may play a role in the higher incidence of chronic disease among them compared with Caucasian American (CA) females. This pilot study aimed to compare the metabolic response of AA and CA females after a high-fat meal. Eleven AA (25.6 (5.6) y, 27.2 (6.0) kg/m2, 27.5 (9.7) % body fat) and twelve CA (26.5 (1.5) y, 25.7 (5.3) kg/m2, 25.0 (7.4) % body fat) women free of cardiovascular and metabolic disease and underwent a high-fat meal challenge (55.9% fat). Lipid oxidation, insulin, glucose, and interleukin (IL)-8 were measured fasted, 2 and 4 h postprandial. AA females had a significantly lower increase in lipid oxidation from baseline to 2 h postprandial (p = 0.022), and trended lower at 4 h postprandial (p = 0.081) compared with CA females, indicating worse MF. No group differences in insulin, glucose or HOMA-IR were detected. IL-8 was significantly higher in AA females compared with CA females at 2 and 4 h postprandial (p = 0.016 and p = 0.015, respectively). These findings provide evidence of metabolic and inflammatory disparities among AA females compared with CA females that could serve as a predictor of chronic disease in individuals with a disproportionately higher risk of development.

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.

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.

Effects of Varying Load Intensity on Skeletal Muscle Damage Between Two Isovolumic Resistance Exercise Bouts.

There are limited data comparing the efficacy of resistance loads within the hypertrophy range for promoting muscular growth, particularly when similar training volumes are utilized. The purpose of this study was to determine if two similar volume-loads, utilizing different intensities, would produce dissimilar muscular damage and inflammation. Eleven resistance-trained, college-aged males participated in this study. After testing 1RM barbell squats, participants completed two similar volume-load barbell squat sessions at two different resistance loads (67% and 85% of 1RM) on two separate visits. Venous blood samples were collected at baseline and one hour after completion of each exercise session. Plasma was isolated and analyzed for myoglobin and C-reactive protein (CRP) expression via ELISA. Plasma myoglobin expression was significantly elevated above baseline (BASE) values only after the 85% of 1RM (HHL) session (p =0.031), though the 67% (LHL) trial (p = 0.054; η2 = 0.647) was approaching significance (BASE: 1.42±.12 ng/mL; LHL: 4.65±1.13 ng/mL; HHL: 5.00±1.01 ng/mL). No changes in plasma CRP were observed. Despite attempts to equate volumes between resistances, mean total volume-load was significantly higher during the 67% of 1RM trial than during the 85% trial. Resistance loads at 85% of 1RM inflict significantly increased muscle damage over baseline values, even when significantly less total volume was lifted during the 85% trial. Individuals looking to maximize strength and hypertrophy during general training or during rehabilitation may benefit from these findings when determining the appropriate training load.

Comparing Physical Fitness in Career vs. Volunteer Firefighters.

ABSTRACT: Morris, CE, Arnett, SW, and Winchester, LJ. Comparing physical fitness in career vs. volunteer firefighters. J Strength Cond Res 36(5): 1304-1309, 2022-The purpose of this study was to assess the potential similarities and differences in health and physical fitness profiles between career firefighters (CFF) and volunteer firefighters (VFF). The research protocol consisted of a health and physical fitness assessment, testing the 5 components of health-related fitness using previously published and accepted protocols. The subject population consisted of a total of 138 firefighters, including 119 CFF and 19 VFF. Statistical significance was defined as a p level less than 0.05. An independent t test showed evidence of CFF having a significantly higher value/score for the following variables: height (p = 0.034), V̇o2max (p = 0.006), push-ups completed (p = 0.024), and plank time (p < 0.001). Volunteer firefighters had a significantly higher value for the following variables: fat mass (p = 0.002), body fat percentage (p < 0.001), and absolute grip strength (p = 0.029). There were no significant differences between groups for the following variables: age (p = 0.299), body mass (p = 0.166), fat-free mass (p = 0.281), body mass index (p = 0.057), flexibility (p = 0.106), or relative grip strength (p = 0.887). With regard to physical fitness testing, the VFF had a significantly worse fitness profile across a number of variables than the CFF. Practical applications: Despite the financial and commitment status of volunteer firefighting departments, their members perform an equally dangerous and important job as do firefighters of professional/career firefighting departments, and more attention should be directed toward developing the fitness and performance of these firefighters.

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.

High-fat meal increases peripheral blood mononuclear cell pro-inflammatory cytokine expression in African-American women.

African-American (AA) women have elevated predominance of inflammatory diseases concurrent with local inflammation resulting in compromised metabolic function. The purpose of the study was 2-fold: 1) to examine the gene and protein expression of pro- and anti-inflammatory cytokine secretion by peripheral blood mononuclear cells (PBMC) obtained from AA and Caucasian-American (CA) women in response to an acute high-fat meal; and 2) to explore the influence of race (AA vs. CA) on PBMC reactivity. Ten AA and 11 CA women consumed a high-fat meal with baseline and 4 h postprandial venous blood draws. PBMCs were incubated for 3 h then messenger RNA expression and supernatant protein concentration was used to examine inflammatory profiles. All women had a postprandial increase in interleukin (IL)-8 gene expression, IL-8 protein concentration, and tumor necrosis factor alpha (TNF-α) protein concentration (P < 0.05). AA women had a postprandial increase in IL-6, IL-8, and TNF-α protein concentration (P < 0.05). AA women had higher postprandial IL-1ß protein concentration and IL-8 gene expression compared with CA women (P < 0.05). Our data uncovers the specific impact of race and time on pro-inflammatory PBMC (IL-1ß, IL-6, IL-8, and TNF-α) expression profiles in response to an acute high-fat meal challenge. Novelty: African Americans have higher predominance of inflammatory disease. We explored the potential race impact on peripheral blood mononuclear cell reactivity in response to a meal. A pro-inflammatory response to an acute high-fat meal with race impact was observed possibly contributing to health disparities impacting African-American women.

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

The aim was to examine the validity of heart rate variability (HRV) measurements from photoplethysmography (PPG) via a smartphone application pre- and post-resistance exercise (RE) and to examine the intraday and interday reliability of the smartphone PPG method. Thirty-one adults underwent two simultaneous ultrashort-term electrocardiograph (ECG) and PPG measurements followed by 1-repetition maximum testing for back squats, bench presses, and bent-over rows. The participants then performed RE, where simultaneous ultrashort-term ECG and PPG measurements were taken: two pre- and one post-exercise. The natural logarithm of the root mean square of successive normal-to-normal (R-R) differences (LnRMSSD) values were compared with paired-sample t-tests, Pearson product correlations, Cohen's d effect sizes (ESs), and Bland-Altman analysis. Intra-class correlations (ICC) were determined between PPG LnRMSSDs. Significant, small-moderate differences were found for all measurements between ECG and PPG: BasePre1 (ES = 0.42), BasePre2 (0.30), REPre1 (0.26), REPre2 (0.36), and REPost (1.14). The correlations ranged from moderate to very large: BasePre1 (r = 0.59), BasePre2 (r = 0.63), REPre1 (r = 0.63), REPre2 (r = 0.76), and REPost (r = 0.41)-all p < 0.05. The agreement for all the measurements was "moderate" (0.10-0.16). The PPG LnRMSSD exhibited "nearly-perfect" intraday reliability (ICC = 0.91) and "very large" interday reliability (0.88). The smartphone PPG was comparable to the ECG for measuring HRV at rest, but with larger error after resistance exercise.

Blood Flow Restriction at High Resistance Loads Increases the Rate of Muscular Fatigue, but Does Not Increase Plasma Markers of Myotrauma or Inflammation.

Winchester, LJ, Morris, CE, Badinger, J, Wiczynski, TL, and VanWye, WR. Blood flow restriction at high resistance loads increases the rate of muscular fatigue, but does not increase plasma markers of myotrauma or inflammation. J Strength Cond Res 34(9): 2419-2426, 2020-High-load resistance training and blood flow restriction (BFR) training at low loads both promote protein synthesis and growth through different cell signaling mechanisms. Therefore, co-activation of these pathways could result in a synergistic effect for additional growth enhancement. The purpose of this study was to evaluate how BFR effects performance and physiological responses after an acute bout of high-load barbell squat training. Twelve resistance-trained, college-aged men and women performed 5 sets of barbell squats at 75% of 1 repetition maximum until failure under traditional (TRAD; control) or intermittent BFR conditions. Perceived limb pain and number of repetitions performed were recorded after each set. Blood samples were collected at baseline and 1-hour postexercise after each trial for analysis of myoglobin and interleukin-6 (IL-6). An alpha level of p < 0.05 was used to determine significance. Blood flow restriction trial performance significantly declined at set 3 and was lower than performance during control, whereas control performance did not decrease until set 5. Perceived limb pain was statistically increased with BFR use for the whole trial and was significantly higher with BFR during set 3 than observed during TRAD. Plasma myoglobin and IL-6 were significantly increased after both trials when compared with baseline, but were not significantly different between trials. Intermittent BFR use during high-load barbell squats increases the rate of muscular fatigue and perceived limb pain, but does not increase muscular damage or inflammatory response. Data obtained from this study can be used by fitness professionals as a means of potentially enhancing the rate of muscular hypertrophy.

Changes in Heart Rate Variability and Fatigue Measures Following Moderate Load Resistance Exercise.

The purpose of this study was to determine the relationship between changes in heart rate variability (HRV), neuromuscular performance, and fatigue biomarkers in response to a resistance exercise bout. The root mean square of successive RR interval differences (RMSSD), neuromuscular performance - isometric handgrip (IHG), countermovement jump (CMJ), mean propulsive velocity (MPV) - metabolic stress (lactate [Lac]) and inflammation (interleukin-6 [IL-6]) were measured in 30 subjects who performed 6×10 back squat (BS), 3×10 bench press (BP), and 3×10 bent-over rows (BR) at 70% of 1-repetition maximum (1RM). The RMSSD, neuromuscular performance, and biomarkers were measured 10 min pre-exercise and 30 min post-exercise (Post30); HRV and Lac were also measured immediately post-exercise (Post0). Pre- versus post-exercise differences were evaluated using paired-samples t-tests. Pearson's correlations were used to determine the association between changes. With the exception of IL-6 (P=0.296) and MPVBP (P=0.678), LnRMSSD, neuromuscular performance, and metabolic stress were different post- compared to pre-exercise. We observed moderate associations between ΔLnRMSSD Post0 and ΔLac Post0 (r = -0.44) and ΔLac Post30 (r = -0.55), respectively. Practitioners should use multiple training load indicators to gain an accurate depiction of recovery.

Effect of a simulated tactical occupation task on physiological strain index, stress and inflammation.

Background. This study aimed to evaluate the physiological strain index (PSI) along with specific immune system markers in response to a simulated firefighting occupation workload. Methods. Ten healthy male adults completed a 6-min simulated fire stair climb (SFSC) at 60 steps/min. The protocol consisted of four conditions, some including wearing a 34.04-kg vest to simulate personal protective equipment (PPE) and/or inclusion of a color-word interference test (CWIT) as a distracting mechanism. The PSI was evaluated by continuously monitoring the heart rate and core temperature. Salivary cortisol (CORT) was measured at baseline, mid SFSC and post SFSC. C-reactive protein (CRP) was evaluated at baseline and 1 h post SFSC. Results. Repeated-measures analysis of variance showed a significantly different PSI across conditions (p = 0.001). A significantly elevated PSI was exhibited during all 6 min of SFSC for both PPE and PPE + CWIT conditions. Neither CORT (p = 0.116) nor CRP (p = 0.700) was significantly different across conditions or from baseline. Conclusion. These findings suggest that firefighters are potentially at a substantial degree of physiological stress from exercise and the weight of gear alone. Further work should be conducted to further evaluate the usefulness of the PSI as a means to monitor firefighters during fire suppression.