Influence of Body Composition, Load-Velocity Profiles, and Sex-Related Differences on Army Combat Fitness Test Performance.

ABSTRACT: Boffey, D, DiPrima, JA, Kendall, KL, Hill, EC, Stout, JR, and Fukuda, DH. Influence of body composition, load-velocity profiles, and sex-related differences on army combat fitness test performance. J Strength Cond Res 37(12): 2467-2476, 2023-The Army Combat Fitness Test (ACFT) became the U.S. Army's mandatory physical fitness test in April of 2022. The purpose of this study was to determine the relationship between ACFT performance and both body composition and velocity profiles and to determine sex differences for these variables. Data were collected at 2 timepoints 4 months apart, from male (n = 55) and female (n = 17) Army Reserve Officers' Training Corps (ROTC) cadets. Body composition was assessed with a bioelectrical impedance spectroscopy device, and cadets completed a hex bar deadlift load-velocity profile (LVP) and ACFT on separate days. Stepwise multiple regressions were used to explain the amount of variance in ACFT total score and individual event performance. Significance for statistical tests was defined as an alpha level of p ≤ 0.05. Muscle mass and body fat percentage accounted for 49% of shared variance of total ACFT score, and deadlift maximal power and maximal velocity accounted for 67% of shared variance of total ACFT score. The 3 repetition maximum deadlift, standing power throw, hand-release push-up, and sprint-drag-carry events favored cadets with more muscle mass, whereas the leg tuck was influenced by the body fat percentage and the 2-mile run was affected by fat mass. Sex had greater predictive capability for the 2-mile run than body composition. Men outperformed women on all individual events, with the greatest differences on standing power throw and sprint-drag-carry. It is recommended that Army ROTC cadets taking the ACFT maximize lower-body power production and increase muscle mass.

Efficacy of Rest Redistribution During Squats: Considerations for Strength and Sex.

ABSTRACT: Boffey, D, Clark, NW, and Fukuda, DH. Efficacy of rest redistribution during squats: Considerations for strength and sex. J Strength Cond Res 35(3): 586-595, 2021-This study examined the kinematic, perceptual, and heart rate responses to rest redistribution (RR) and traditional sets (TS) during the barbell back squat for men and women possessing a wide range of strength levels. Forty-five resistance-trained subjects (30 men and 15 women) performed 40 repetitions of the barbell squat with 65% 1RM load with TS (4 × 10 repetitions, 3-minute rest) or RR (10 × 4 repetitions, 1-minute rest), in a randomized order on days separated by ≥72 hours. The significance was set at p ≤ 0.05 for all statistical analyses. The mean velocity (MV) maintenance was significantly higher for RR compared with TS (87.70 ± 4.50% vs. 84.07 ± 4.48%, respectively; p < 0.01, d = 0.35). Rating of perceived exertion (active muscles) was significantly lower for RR compared with TS (5.38 ± 1.42 vs. 6.08 ± 1.43, respectively; p = 0.02, d = -0.35). Rating of perceived exertion (overall) was also significantly lower for RR compared with TS (5.60 ± 1.40 vs. 6.48 ± 1.49, respectively; p = 0.02, d = -0.37). The relative strength ratio (relative strength ratio; squat 1RM: body mass) was significantly correlated with the difference in MV maintenance between RR and TS (r = -0.34, p = 0.02). No sex-based differences (p > 0.05) were found for any dependent variables. Rest redistribution produced significantly higher mean HR (143.25 ± 21.11 vs. 135.05 ± 20.74, p < 0.01) and minimum HR (102.77 ± 19.58 vs. 95.97 ± 22.17, p < 0.01). Subjects were better able to maintain velocity with RR compared with TS, while experiencing less perceived effort. Rest redistribution can be recommended for both men and women, but very strong individuals may not improve their velocity maintenance with RR to the same extent as less strong individuals.

Effects of High-Dose, Short-Duration ß-Alanine Supplementation on Cognitive Function, Mood, and Circulating Brain-Derived Neurotropic Factor (BDNF) in Recreationally-Active Males Before Simulated Military Operational Stress.

Introduction: ß-alanine (BA) supplementation may improve cognition and mitigate symptoms of anxiety and depression associated with aging, neurological disorders, and physical exertion, which has been attributed to increases in brain carnosine and/or brain-derived neurotropic factor (BDNF). BA also provides beneficial effects on cognition, mood, and physical performance during military operations; however, whether BA can attenuate mood disruptions and cognitive dysfunction associated with the anticipatory stress prior to simulated military operations is unknown.Purpose: The present study examined the effects of 14 days of BA (12 g·day-1) supplementation on cognitive function, mood, and circulating BDNF concentrations in recreationally-active, healthy males with limited inflammation and oxidative stress prior to a 24h simulated military operation.Methods: Participants were randomized into BA (n = 10) or placebo (n = 9; PL) for 14 days. Cognitive function, mood, and circulating BDNF were assessed before (PRE) and after (POST) supplementation. Cognition was assessed via multiple object tracking (Neurotracker™), visuomotor reaction time (Dynavision™), mathematical processing (Serial Subtraction Test), and neuropsychological assessments (ANAM™). Mood was assessed using the Profile of Mood States (POMS) questionnaire. After POST testing, subjects underwent a 24h simulated military operation.Results: No change in measures of cognitive function or BDNF concentrations were observed (p > 0.05). However, BA experienced significant reductions (p = 0.046) in subjective feelings of depression, while PL experienced significant reductions (p = 0.021) in feelings of vigor from PRE to POST.Conclusions: High-dose, short-duration BA supplementation does not appear to affect cognitive function or circulating BDNF, but may mitigate the onset of negative mood states in healthy, recreationally-active males prior to a simulated military operation.

Effect of ß-Alanine Supplementation on Monocyte Recruitment and Cognition During a 24-Hour Simulated Military Operation.

Wells, AJ, Varanoske, AN, Coker, NA, Kozlowski, GJ, Frosti, CL, Boffey, D, Harat, I, Jahani, S, Gepner, Y, and Hoffman, JR. Effect of ß-alanine supplementation on monocyte recruitment and cognition during a 24-hour simulated military operation. J Strength Cond Res 34(11): 3042-3054, 2020-Sustained military operations (SUSOPs) result in psychological stress and cognitive dysfunction, which may be related to the recruitment of classical monocytes into the brain. This study examined the effect of beta-alanine (BA) on cognition and monocyte recruitment during a simulated 24-hour SUSOP. Nineteen healthy men ingested 12-g/d BA or placebo for 14 days before an SUSOP. Monocyte chemoattractant protein-1 (MCP-1), C-C chemokine receptor-2 (CCR2), and macrophage-1-antigen (CD11b) expression were assessed through multiplex assay and flow cytometry. Psychological stress and cognition were assessed through Automated Neuropsychological Assessment Metrics (ANAM). A composite measure of cognition (COGcomp) was generated from throughput scores extracted from 7 ANAM cognitive tests. Assessments occurred at baseline (0H), 12 hours (12H), 18 hours (18H), and 24 hours (24H). Significance was accepted at p ≤ 0.05. No significant effect of BA was noted for any variable (p's > 0.05). The frequency and severity of symptoms of psychological stress increased significantly at 18 and 24H compared with 0 and 12H (p's < 0.05). COGcomp decreased significantly at 18 and 24H compared with 0 and 12H (p's ≤ 0.001). MCP-1 peaked at 18H was significantly lower at 24H compared with 18H but remained elevated at 24H compared with 0H (p's < 0.001). CCR2 expression was significantly lower at 12 (p = 0.031), 18, and 24H (p's < 0.001). CD11b expression was significantly higher at 12H (p = 0.039) and 24H (p's = 0.003). MCP-1 was negatively associated with COGcomp (ß = -0.395, p = 0.002, r2 = 0.174). Neither CCR2 or CD11b was related to COGcomp (p's > 0.05). Cognitive dysfunction during SUSOPs is related to serum concentrations of MCP-1 but is not influenced by BA supplementation.

Dynamic post-activation potentiation protocol improves rowing performance in experienced female rowers.

Post-activation potentiation likely acutely improves power-based performance; however, few studies have demonstrated improved endurance performance. Forty collegiate female rowers performed isometric potentiating (ISO), dynamic potentiating (DYN) and control (CON) warm-up protocols on a rowing ergometer, followed by a three-minute all-out test to evaluate their total distance, peak power, mean power, critical power, anaerobic working capacity (W') and stroke rate. Fifteen-second splits were also analysed. ISO consisted of 5 × 5-second static muscle actions with the ergometer handle rendered immovable with a nylon strap, while DYN consisted of 2 × 10-second all-out rowing bouts, separated by a 2-minute rest interval. The participants were divided into high and low experience groups by median experience level (3.75 years) for statistical analysis. Significant differences (DYN > CON; p < 0.05) were found for distance (+5.6 m), mean power (+5.9 W) and W' (+1561.6 J) for more experienced rowers (n = 19) and no differences for less experienced rowers (n = 18). Mean power in DYN was significantly greater than CON and ISO in the 15-30, 30-45, 45-60 and 60-75 second intervals independent of experience level. These results suggest that DYN may benefit experienced female rowers and that these strategies might benefit a greater power output over shorter distances regardless of experience.

Effects of Load on Peak Power Output Fatigue During the Bench Throw.

Boffey, D, Sokmen, B, Sollanek, K, Boda, W, and Winter, S. Effects of load on peak power output fatigue during the bench throw. J Strength Cond Res 33(2): 355-359, 2019-The ability to create power is an important variable for athletic success. No study to date has compared peak power output (PPO) fatigue across multiple sets and with different loads with the bench throw. This study aimed to begin the process of establishing empirical upper-body power training guidelines for moderately strong athletes by determining how load (30, 45, and 60% 1 repetition maximum [1RM]) affects PPO (Watts) dropoff during 3 sets of 10 repetitions of the bench throw. Ten resistance-trained male volunteers ([mean ± SD]: age 20.58 ± 1.36 years, height 176.05 ± 9.09 cm, body mass 78.65 ± 9.93 kg, bench press 1RM 99.79 ± 18.52 kg) performed 3 sets of 10 repetitions of the bench throw with one of the 3 loads during 3 weekly sessions. A Humac 360 device collected concentric phase PPO data during each repetition. The data were analyzed using one-way (treatment) and 2-way (treatment × time) repeated-measures analysis of variance. A significant decrease in PPO was observed during repetitions 5-7 at 30%, 3-4 at 45%, and 2-3 at 60% 1RM. Based on the results of this study, coaches who want to maximize power should potentially keep sets of upper-body plyometrics within these repetition ranges. The authors recommend that moderately strong athletes perform the bench throw on a Smith machine at 45% or 60% 1RM to produce high PPO over multiple sets.

The Physiology and Biomechanics of Load Carriage Performance.

Introduction: The weight that soldiers are required to carry in training and in combat has continually increased over the years. Changes in load carried or pace of activity will alter the physiological and biomechanical stress associated with the activity. Whether it is part of the soldier's training or an actual operation, managing the proper load and speed to minimize fatigue can be integral to the soldier's success. Without a proper understanding of the multitude of factors that may affect load carriage performance, mission success may be jeopardized. The purpose of this review is to summarize and clarify the findings of load carriage research and to propose a new method for analyzing the intensity of load carriage tasks, the Load-Speed Index. Materials and Methods: We reviewed studies that examined military load carriage at walking speeds and included articles that featured non-military participants as deemed necessary. Results: Major factors that can affect load carriage performance, such as speed of movement, load carried, load placement, body armor, and environmental extremes all influence the soldier's energy expenditure. A critical aspect of load carriage performance is determining the appropriate combination of speed and load that will maximize efficiency of the activity. At the higher end of walking speeds, the walk-to-run transition represents a potential problem of efficiency, as it may vary on an individual or population basis. Conclusions: This review provides a comprehensive overview of these factors and suggests a new Load-Speed Index, which can be utilized to define thresholds for load and speed combinations and contribute to the understanding of the physiological and biomechanical demands of load carriage marches. The literature recommends that load and speed should be managed in order to maintain an exercise intensity ~45% VO2 max to delay time to fatigue during prolonged marches, and the Load-Speed Index corroborated this finding, identifying 47% VO2 max as a threshold above which intensity increases at a greater rate with increases in load and speed. The Load-Speed Index requires validation as a predictive tool. There are no definitive findings as to how load affects the speed at which the walk-to-run transition occurs, as no investigations have specifically examined this interaction. Additional research is clearly needed by examining a wide range of loads that will facilitate a clearer understanding of speed and load combinations that optimize marching pace and reduce energy expenditure.

Benefits of ß-hydroxy-ß-methylbutyrate supplementation in trained and untrained individuals.

ß-Hydroxy-ß-Methylbutyrate (HMB) is a metabolite of the branched-chain amino acid leucine and its ketoacid α-ketoisocaproate. HMB has been widely used as an ergogenic supplement to increase muscle strength, muscle hypertrophy and enhance recovery. The physiological mechanisms that underlie these benefits are related to HMB's ability to stimulate muscle protein synthesis and minimize muscle breakdown. Although evidence supporting the benefits of HMB supplementation is not conclusive, many of these studies have suffered from methodological flaws including different formulations, supplement duration and population studied. HMB in its free acid formulation is suggestive of having a greater potential for efficacy in both trained and untrained populations than its calcium-salt form. However, the evidence regarding HMB's role in limiting muscle degradation and increasing muscle protein synthesis has created an exciting interest in examining its efficacy among untrained individuals. Recent investigations examining intense training have demonstrated efficacy in maintaining muscle mass and attenuating the inflammatory response.

Effects of ß-alanine supplementation on physical performance, cognition, endocrine function, and inflammation during a 24 h simulated military operation.

Sustained military operations (SUSOPs) are associated with performance decrements and cognitive dysfunction. ß-Alanine (BA) supplementation may have a role in increasing soldier resiliency by enhancing muscle-buffering capacity and reducing oxidative stress. The purpose of this study was to examine the effects of BA on physical performance, cognition, endocrine function, and inflammation during a 24 h simulated SUSOP. Nineteen males were randomized into one of two groups: BA (n = 10) or placebo (n = 9; PLA) (12 g/day) for 14 days preceding the 24 h SUSOP. Assessments were performed at 0 h (0H), 12 h (12H), and 24 h (24H) during the SUSOP. No changes in visual tracking ability, jump power, or upper-body muscular endurance were observed between groups or time points (P's > 0.05). Increases in subjective feelings of soreness and fatigue were noted at 12H compared to 0H (P < 0.05) in PLA, but not in BA. Visual reaction time for PLA was slower at 24H compared to 0H (P = 0.035), and PLA made more errors on reaction time testing at 12H compared to BA (P = 0.048), but motor reaction time was faster (P = 0.016) for PLA. Simulated litter carry and 1 km run completion times increased at 24H compared to 0H in both groups (P < 0.05), however, PLA had a longer 1 km time compared to BA at 24H (P = 0.050). Increases in inflammatory and endocrine markers were observed over the SUSOP, with no differences between groups. BA supplementation appears to maintain some aspects of cognition and physical performance during a 24 h SUSOP, with no effects on endocrine function or inflammation.