Importance:Musculoskeletal injuries (MSKIs) are pervasive problems in novice training environments. Evaluation of modifiable and nonmodifiable risk factors of MSKI risk prior to entry into these environments is largely understudied. Objective:To provide military leaders, civilian and military clinicians, and physical training instructors with an MSKI risk model for identifying low-, moderate-, and high-risk profiles among individuals starting US Army Basic Combat Training (BCT) or a physical training program. Design, Setting, and Participants:In this prospective cohort study, data collection was conducted between August 5, 2017, and April 15, 2023, at 2 US Army BCT sites. The sample consisted of volunteer trainees between the ages of 17 and 41 years. They were followed up from the start of BCT. Data analyses were conducted from April to September 2024. Exposures:Data for the factors potentially associated with MSKI were collected during the first week of BCT and included blood draws, total body dual-energy x-ray absorptiometry, and muscle power test results; surveys of demographics, medical history, physical activity, psychological characteristics, and sleep patterns; and physical fitness results. Main Outcomes and Measures:MSKIs identified using International Statistical Classification of Diseases and Related Health Problems, Tenth Revision (ICD-10) codes. Logistic regression-based models estimating the risk of MSKI were generated using 5-fold internal cross-validation for the total cohort, males, and females. Traffic light model examples of low (green), moderate (amber), and high (red) MSKI risk tiers were produced. Results:In this cohort study of 2988 Army trainees (median [IQR] age, 19.0 [19.0-22.0] years; 1880 males [62.9%]), 729 females (49.0%) and 758 males (51.0%) had an ICD-10 code-identified MSKI, and 1067 (35.7%) had more than 1 ICD-10 code-identified MSKI. Factors associated with increased MSKI risk in the total cohort and female- and male-specific MSKI risk models (with areas under the receiver operator characteristic curve of 0.701, 0.678, and 0.661, respectively) encompassed 7 variable categories: demographics; anthropometrics and body composition; nutritional status; medical and health history; history of sports and past or current physical activity or fitness; psychological factors (ie, pain, grit, and hardiness); and sleep parameters. Conclusions and Relevance:This cohort study presents a tiered approach to identifying persons at increased MSKI risk before the start of a physical training program. Applying a tiered quantification risk metric and incorporating multifactorial interventions from these findings may play a role in reduced MSKI risk.

Background Body composition influences physical fitness (PF) and risk of musculoskeletal injury (MSKI). Assessing the relationship between body fat (BF), PF and MSKI risk in a large diverse military population may provide evidence basis informing health-care policies, practices, and programs for military and civilian populations. Objective Evaluate the validity of expedient methods to estimate BF (e.g., circumference-based equation (CBE) and bioelectrical impedance analysis (BIA)) and investigate relationships between BF and PF with MSKI risk in a large diverse population. Methods Participants were 1904 active-duty Soldiers (643 F) representing Army demographics sex, race/ethnicity (R/E), and age. PF, defined as the most recent Army Combat Fitness Test (ACFT) score and incidence of MSKI, were obtained from Army records. BF was determined by dual-energy x-ray absorptiometry (%BFDXA), bioelectrical impedance analysis (%BFBIA), and CBE using 3-site (Hodgdon, %BFHE) and 1-site (Taylor-McClung, %BFTM) equations. Results were stratified by race and sex, to evaluate differences in accuracy of estimated %BF (weighted root mean squared error from %BFDXA). Associations of BF and PF with MSKI risk were evaluated with logistic regression. Results CBE and BIA underestimated %BF compared to %BFDXA. %BFBIA differed from %BFDXA overall and by sex. %BFTM underestimation was uniform across both sex and R/E compared to %BFDXA. Mean differences from %BFDXA by sex (M;F) were lower when measured by %BFTM (4.38; 4.59) compared to %BFHE (5.88; 4.39). Individuals had a greater likelihood of MSKI if they failed BF standards (odds ratio 1.32). Scoring >= 540 total on ACFT exhibited a 31% (95% CI: 0.52, 0.92) lower MSKI risk during the following 12 months than those with a lower score. Conclusions A single-site BF equation (%BFTM) maintained similar accuracy across the Soldier population by sex, age, and R/E. Implementing a PF score threshold in lieu of passing Army BF standards was associated with lower MSKI risk.

Energy deficit often occurs during military training and operations due to prolonged and strenuous physical exertion and limited access to food. During energy deficit, the body predominately relies on fat stores. This results in greater circulating acylcarnitine species as acyl groups are moved into the mitochondria for β-oxidation. Carnitine and acylcarnitine species have not been assessed during prolonged energy deficit and following a recovery period in healthy males undergoing strenuous military training. The objective of this study was to determine longitudinal changes in plasma carnitine and aclycarnitines following a prolonged and severe energy deficit and short-term recovery. This secondary analysis examined plasma carnitine and acylcarnitine concentrations before (PRE) and after (POST) 61-day U.S. Army Ranger training and following 2 weeks of recovery (REC). During training, participants (n = 22; mean ± standard deviation: 23.2 ± 2.8 years; 81.7 ± 9.3 kg; 16.5 ± 6.8% body fat) consumed ∼2200 kcal/day and were in an ∼1000 kcal/day energy deficit. Carnitine and acylcarnitine (C2-C22) concentrations were measured by tandem mass spectrometry. At POST, participants had increased concentrations of total short-chain acylcarnitines and 10 of 58 acylcarnitine species (C2, C5, C8-dicarboxylic acid (DC), C16:1, C16:1-hydroxyl group (OH), C18:1-OH, C18:1-DC, C18:2-OH, C20:2-OH, C22:3; P ≤ 0.05) compared to PRE. These acylcarnitine species returned to PRE concentrations following REC (P > 0.05). Greater bodyweight loss was associated with greater increases in short-chain acylcarnitine (r = -0.68; P = 0.0006), medium-chain acylcarnitine (r = -0.61; P = 0.0035), and long-chain acylcarnitine (ρ = -0.65; P = 0.0013) concentrations. Severe energy deficit incurred during strenuous military training increased 10 acylcarnitine species. However, 2 weeks of recovery was sufficient for acylcarnitine concentrations to return to baseline concentrations.

Looney, DP, Hoogkamer, W, Kram, R, Arellano, CJ, and Spiering, BA. Estimating metabolic energy expenditure during level running in healthy, military-age women and men. J Strength Cond Res 37(12): 2496-2503, 2023-Quantifying the rate of metabolic energy expenditure (.) of varied aerobic exercise modalities is important for optimizing fueling and performance and maintaining safety in military personnel operating in extreme conditions. However, although equations exist for estimating oxygen uptake during running, surprisingly, there are no general equations that estimate.. Our purpose was to generate a general equation for estimating. during level running in healthy, military-age (18-44 years) women and men. We compiled indirect calorimetry data collected during treadmill running from 3 types of sources: original individual subject data (n545), published individual subject data (30 studies; n5 421), and published group mean data (20 studies, n 5 619). Linear and quadratic equations were fit on the aggregated data set using a mixed-effects modeling approach. A chi-squared (x 2) difference test was conducted to determine whether the more complex quadratic equation was justified (p, 0.05). Our primary indicator of model goodness-of-fit was the root-mean-square deviation (RMSD). We also examined whether individual characteristics (age, height, body mass, and maximal oxygen uptake [V.O2max]) could minimize prediction errors. The compiled data set exhibited considerable variability in. (14.54 6 3.52 W center dot kg21), respiratory exchange ratios (0.8960.06), and running speeds (3.5060.86m center dot s21). The quadratic regression equation had reduced residual sum of squares compared with the linear fit (x2, 3,484; p, 0.001), with higher combined accuracy and precision (RMSD, 1.31 vs. 1.33 W center dot kg21). Age (p 5 0.034), height (p 5 0.026), and body mass (p 5 0.019) were associated with the magnitude of under and overestimation, which was not the case for V.O2max (p50.898). The newly derived running energy expenditure estimation (RE3) model accurately predicts level running. at speeds from 1.78 to 5.70 m center dot s21 in healthy, military-age women and men. Users can rely on the following equations for improved predictions of running. as a function of running speed (S, m center dot s21) in either watts (W center dot kg21 5 4.43 + 1.51 center dot S + 0.37 center dot S2) or kilocalories per minute (kcal center dot kg21 center dot min21 5 308.8 + 105.2 center dot S + 25.58 center dot S2).

BACKGROUND: Approximately 16% of the US Army population is women, of which ≥85% fall within childbearing years. Army policy allows women 12 months of recovery from childbirth before return to duty at full compacity. Full return to duty requires women to meet Army body composition (body fat, BF) and physical fitness (PF) standards. Understanding how birth method and time since delivery affect compliance with BF and PF standards may aid female Soldiers in successful return to duty. PURPOSE: Investigate the effects of birth method and time since delivery on compliance with BF and PF standards in Army women. METHODS: Participants were active-duty female Soldiers (644 total, 367 non-pregnant, NP; 277 post-partum, PP). BF was quantified using dual energy x-ray absorptiometry with acceptable BF by Army standards stratified by age in accordance with Army Regulation 600-9. PP medical care (delivery method) and PF scores (Army Combat Fitness Test, most recent total score within 6 months of BF assessment) were attained from a data repository. A Wald chi square was used to assess differences between groups; significance considered at p ≤ 0.05. RESULTS: Of PP population, 190 delivered vaginally (PP-V) and 67 by cesarean (PP-C) (mean difference in time 1.6 yr; p < 0.01). Time since delivery was ≤12 months for 75 PP (53 PP-V, 22 PP-C) and was >12 months for 202 PP (137 PP-V, 45 PP-C). Overall, NP passed BF at a greater rate than PP (70% vs 55%, respectively; P ≤ 0.001); however, the between-group difference in the pass rate for PF was not different (P = 0.051). PP with >12 months since delivery were more likely to pass BF than ≤12 months (57% vs 49%, P ≤ 0.001) with no difference in passing PF (P = 0.364). PP-V had a higher pass rate for BF (P = 0.037) and no difference in passing PT (P = 0.067) compared to PP-C. CONCLUSION: Regardless of birth method, PP women are more likely to meet BF standards if they have 12 months or greater to recover, whereas less recovery time appears needed to meet PT standards. Cesarean delivery may hinder meeting BF standards following birth, but further research is needed to confirm this observation.

Introduction/background As a proxy for adiposity, body mass index (BMI) provides a practical public health metric to counter obesity-related disease trends. On an individual basis, BMI cannot distinguish fat and lean components of body composition. Further, the relationship between BMI and body composition may be altered in response to physical training. We investigated this dynamic relationship by examining the effect of US Army basic combat training (BCT) on the association between BMI and per cent body fat (%BF). Methods BMI and %BF were measured at the beginning (week 1) and end (week 9) of BCT in female (n=504) and male (n=965) trainees. Height and weight were obtained for BMI, and body composition was obtained by dual X-ray absorptiometry. Sensitivity and specificity of BMI-based classification were determined at two BMI thresholds (25 kg/m(2) and 27.5 kg/m(2)). Results A progressive age-related increase in fat-free mass index (FFMI) was observed, with an inflection point at age 21 years. In soldiers aged 21+, BMI of 25.0 kg/m(2) predicted 33% and 29% BF in women and 23% and 20% BF in men and BMI of 27.5 kg/m(2) predicted 35% and 31% BF in women and 26% and 22% BF in men, at the start and end of BCT, respectively. Sensitivity and specificity of BMI-based classification of %BF were poor. Soldiers below BMI of 20 kg/m(2) had normal instead of markedly reduced %BF, reflecting especially low FFMI. Conclusions BCT alters the BMI-%BF relationship, with lower %BF at a given BMI by the end of BCT compared with the beginning, highlighting the unreliability of BMI to try to estimate body composition. The specific BMI threshold of 25.0 kg/m(2), defined as 'overweight', is an out-of-date metric for health and performance outcomes. To the extent that %BF reflects physical readiness, these data provide evidence of a fit and capable military force at BMI greater than 25.0 kg/m(2).

ABSTRACT Basic combat training (BCT) is a physically rigorous period at the beginning of a soldier's career that induces bone formation in the tibia. Race and sex are determinants of bone properties in young adults but their influences on changes in bone microarchitecture during BCT are unknown. The purpose of this work was to determine the influence of sex and race on changes in bone microarchitecture during BCT. Bone microarchitecture was assessed at the distal tibia via high‐resolution peripheral quantitative computed tomography at the beginning and end of 8 weeks of BCT in a multiracial cohort of trainees (552 female, 1053 male; mean ± standard deviation [SD] age = 20.7 ± 3.7 years) of which 25.4% self‐identified as black, 19.5% as race other than black or white (other races combined), and 55.1% as white. We used linear regression models to determine whether changes in bone microarchitecture due to BCT differed by race or sex, after adjusting for age, height, weight, physical activity, and tobacco use. We found that trabecular bone density (Tb.BMD), thickness (Tb.Th), and volume (Tb.BV/TV), as well as cortical BMD (Ct.BMD) and thickness (Ct.Th) increased following BCT in both sexes and across racial groups (+0.32% to +1.87%, all p < 0.01). Compared to males, females had greater increases in Tb.BMD (+1.87% versus +1.40%; p = 0.01) and Tb.Th (+0.87% versus +0.58%; p = 0.02), but smaller increases in Ct.BMD (+0.35% versus +0.61%; p < 0.01). Compared to black trainees, white trainees had greater increases in Tb.Th (+0.82% versus +0.61%; p = 0.03). Other races combined and white trainees had greater increases in Ct.BMD than black trainees (+0.56% and + 0.55% versus +0.32%; both p ≤ 0.01). Changes in distal tibial microarchitecture, consistent with adaptive bone formation, occur in trainees of all races and sexes, with modest differences by sex and race. Published 2023. This article is a U.S. Government work and is in the public domain in the USA. JBMR Plus published by Wiley Periodicals LLC on behalf of American Society for Bone and Mineral Research.

BACKGROUND: Musculoskeletal injuries (MSKI) are the leading cause of medical encounters, disability and manpower losses in the US Army. Higher body fat (BF) is associated with an increased risk for future MSKI. Additionally, a history of MSKI has been linked to increases in BF and higher injury risk. The Army maintains standard BF allowances stratified by age and sex in accordance with Army Regulation 600-9. Currently, there is discussion as to whether Army BF standards require update. Understanding the relationship between these BF standards and MSKI will aid in evaluating these standards. PURPOSE: Investigate the relationship between MSKI and Army BF standards in a representative Army sample. METHODS: Participants were active-duty Soldiers (2690 total, 1801 men, 889 women). BF was quantified using whole body dual energy x-ray absorptiometry and stratified into passing or failing Army BF standards. Diagnoses of duty limiting MSKI in the year before and after BF assessment were attained from the Soldier Performance, Health, and Readiness database. Logistic regression models were used to estimate odds ratios and corresponding 95% confidence intervals (CI) for the relationship between MSKI and BF standards. Future MSKI risk models were adjusted for prior MSKI, age and sex. RESULTS: Approximately 30% of the study population had a MSKI medical profile in the 12 months prior to BF assessment. Soldiers reported a mean loss in duty time of 37 ± 60 days (range 5-1083 days) from MSKI. At the time of BF measurement, mean time since MSKI was 107 ± 117 days. Soldiers that had a prior MSKI were 1.86 (95% CI: 1.52, 2.29) times more likely to go on to fail BF standards (p ≤ 0.001). After BF assessment, 28% of the study population went on to have a new MSKI. Compared to Soldiers who passed BF standards, those who failed had 1.23 times the odds (95% CI: 1.01, 1.51) of developing a new MSKI (p = 0.04) following the assessment with a mean time to injury of 240 ± 123 days. CONCLUSION: Soldiers diagnosed with an MSKI were more likely to fail BF requirements for up to 12 months. Failing BF standards was related to an increased risk of developing an MSKI independent of prior injury history. Disclaimer: The views expressed in this abstract are those of the authors and do not reflect the official policy of the Department of Army, Department of Defense, or the U.S. Government.

Abstract Spiering, BA, Clark, BC, Schoenfeld, BJ, Foulis, SA, and Pasiakos, SM. Maximizing strength: the stimuli and mediators of strength gains and their application to training and rehabilitation. J Strength Cond Res 37(4): 919–929, 2023—Traditional heavy resistance exercise (RE) training increases maximal strength, a valuable adaptation in many situations. That stated, some populations seek new opportunities for pushing the upper limits of strength gains (e.g., athletes and military personnel). Alternatively, other populations strive to increase or maintain strength but cannot perform heavy RE (e.g., during at-home exercise, during deployment, or after injury or illness). Therefore, the purpose of this narrative review is to (a) identify the known stimuli that trigger gains in strength; (b) identify the known factors that mediate the long-term effectiveness of these stimuli; (c) discuss (and in some cases, speculate on) potential opportunities for maximizing strength gains beyond current limits; and (d) discuss practical applications for increasing or maintaining strength when traditional heavy RE cannot be performed. First, by conceptually deconstructing traditional heavy RE, we identify that strength gains are stimulated through a sequence of events, namely: giving maximal mental effort, leading to maximal neural activation of muscle to produce forceful contractions, involving lifting and lowering movements, training through a full range of motion, and (potentially) inducing muscular metabolic stress. Second, we identify factors that mediate the long-term effectiveness of these RE stimuli, namely: optimizing the dose of RE within a session, beginning each set of RE in a minimally fatigued state, optimizing recovery between training sessions, and (potentially) periodizing the training stimulus over time. Equipped with these insights, we identify potential opportunities for further maximizing strength gains. Finally, we identify opportunities for increasing or maintaining strength when traditional heavy RE cannot be performed.

BACKGROUND: The U.S. Army uses a circumference-based equation (CBE) to estimate body fat (%BF) of Soldiers. Since adoption, the Army population has changed, and a re-evaluation of body composition testing is warranted. Modern technology offers increased precision, however the accuracy of newer methods has not been evaluated. PURPOSE: Characterize the accuracy of CBE and bioelectrical impedance (BIA) to estimate %BF compared to dual energy x-ray absorptiometry (DXA), in a diverse Army population. METHODS: Data was collected from 1707 Soldiers (536 females, 1171 males) stratified by age, sex, race/ethnicity. Demographics were: Asian/Pacific Islander (7%), Black (22%), Hispanic (18%), Native American/Alaskan Native (2%), and White (40%); age was categorized as: 17-20, 21-27, 28-39 and ≥ 40. %BF was assessed using BIA, CBE, and DXA. CBE measurements were taken at the neck and abdomen for males, and neck, waist and hips for females, using the Hodgdon equation to calculate %BF, as per the Army Body Composition Program. %BF estimates for BIA and CBE were compared to DXA and reported as mean ± SE, adjusted for age and sex. Analysis by two-way ANOVA was used to determine differences between all groups. Significance is reported as p < 0.01. RESULTS: For BIA and CBE, %BF accuracy improved across age groups compared to DXA (p ≤ 0.05). Compared to DXA, CBE and BIA underestimated %BF in females (1.57 ± 0.16% and 2.99 ± 0.12%, respectively) and males (4.83 ± 0.11% and 3.60 ± 0.08%, respectively). CBE accuracy did not differ by race compared to DXA. BIA showed differences in %BF estimation between all RE groups except Native American compared to DXA. For females, Black and Hispanic differed from White in %BF by BIA compared to DXA. For males, Asian, Black and Hispanic differed from White, and Black differed from Hispanic in %BF by BIA compared to DXA. CONCLUSION: The CBE method of estimating %BF is accurate within 5% BF, and BIA 4% BF compared to DXA in this diverse population. Modern technology offers advances in accuracy, however drawbacks such as cost, time, and training, must be considered. CBE remains an accurate and efficient method of measuring %BF. Disclaimer: The views expressed in this abstract are those of the authors and do not reflect the official policy of the Department of Army, Department of Defense, or the U.S. Government.

In 1981, the US military adopted body fat standards to promote physical readiness and prevent obesity. Separate circumference-based equations were developed for women and men. Both predictive equations were known to underestimate %BF. However, it was not known how well these abdominal circumference-based methods tracked changes in %BF. This study examined the validity of the circumference-based %BF equations for assessing changes in %BF in young adult recruits during Army Basic Combat Training (BCT). Dual-energy X-ray absorptiometry (DXA) and circumference-based measures of %BF were obtained in women (n = 481) and men (n = 926) at the start (pre-BCT) and end (post-BCT) of 8 weeks of BCT. Repeated-measure ANOVAs were used to assess differences between DXA and circumference pre-BCT and for the change during BCT. Pre-BCT, circumferences underestimated %BF relative to DXA, with mean errors of −6.0% ± 4.4% for women and −6.0% ± 3.5% for men (both p < 0.01), and no difference between sexes was observed (p = 0.77). DXA detected a −4.0% ± 2.4% and −3.3% ± 2.8% change in %BF for women and men in response to BCT, respectively (both p < 0.01), whereas circumference estimates of %BF indicated a 0.0% ± 3.3% (p = 0.86) change in women and a −2.2% ± 3.3% (p < 0.01) change in men (sex difference by technique p < 0.01). In conclusion, circumference-based measures underestimated %BF at the start of BCT in both sexes as compared to DXA. Circumference measures underestimated changes in %BF during BCT in men and did not detect changes in women. These findings suggest that circumference-based %BF metrics may not be an appropriate tool to track changes in body composition during short duration training.

Athletes can face scenarios in which they are confined to bed rest (e.g., due to injury or illness). Existing research in otherwise healthy individuals indicates that those entering bed rest with the greatest physical performance level might experience the greatest performance decrements, which indirectly suggests that athletes might be more susceptible to the detrimental consequences of bed rest than general populations. Therefore, a comprehensive understanding of the effects of bed rest might help guide the medical care of athletes during and following bed rest. This systematic and narrative review aimed to (1) establish the evidence for the effects of bed rest on physical performance in athletes; (2) discuss potential countermeasures to offset these negative consequences; and (3) identify the time-course of recovery following bed rest to guide return-to-sport rehabilitation. This review was performed using the Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA) guidelines. Four databases were searched (SPORTDiscus, Web of Science, Scopus, and MEDLINE/PubMed) in October of 2022, and studies were included if they were peer-reviewed investigations, written in English, and investigated the effects of horizontal bed rest on changes in physical capacities and qualities in athletes (defined as Tier 3–5 participants). The reporting quality of the research was assessed using a modified version of the Downs Black checklist. Furthermore, findings from studies that involved participants in Tiers 1–2 were presented and synthesized using a narrative approach. Our systematic review of the literature using a rigorous criterion of ‘athletes’ revealed zero scientific publications. Nevertheless, as a by-product of our search, seven studies were identified that involved apparently healthy individuals who performed specific exercise training prior to bed rest. Based on the limited evidence from studies involving non-athletes who were otherwise healthy prior to bed rest, we generally conclude that (1) bed rest rapidly (within 3 days) decreases upright endurance exercise performance, likely due to a rapid loss in plasma volume; whereas strength is reduced within 5 days, likely due to neural factors as well as muscle atrophy; (2) fluid/salt supplementation may be an effective countermeasure to protect against decrements in endurance performance during bed rest; while a broader array of potentially effective countermeasures exists, the efficacy of these countermeasures for previously exercise-trained individuals requires further study; and (3) athletes likely require at least 2–4 weeks of progressive rehabilitation following bed rest of ≤ 28 days, although the timeline of recovery might need to be extended depending on the underlying reason for bed rest (e.g., injury or illness). Despite these general conclusions from studies involving non-athletes, our primary conclusion is that substantial effort and research is still required to quantify the effects of bed rest on physical performance, identify effective countermeasures, and provide return-to-sport timelines in bona fide athletes. Registration ID: osf.io/d3aew; Date: October 24, 2022.

INTRODUCTION The U.S. Army Occupational Physical Assessment Test (OPAT) is a pre-enlistment physical employment screening assessment developed to place recruits and soldiers into Military Occupational Specialties (MOSs) based on their physical capabilities in order to optimize performance and limit injury. The OPAT consists of the seated power throw (SPT), strength deadlift (SDL), standing long jump, and interval aerobic run. During the scientific validation of the OPAT, two variants of the SPT and two variants of the SDL were used. Although the OPAT was validated using both variants for each test, U.S. Army scientists and policymakers have received queries regarding how these variants compare to each other. Therefore, the purpose of this study was to compare different variants of the SPT and SDL. MATERIALS AND METHODS Thirty-two participants (14 male and 18 female) between the ages of 18 and 42 years visited the laboratory on one occasion and performed two variants of the SPT (seated on the ground [the current OPAT standard] versus seated in a chair with a 35 cm seat height) and two variants of the SDL (using a hex-bar [the current OPAT standard] versus using paired dumbbells). Testing order for the different variants was randomized. The protocol was approved by the U.S. Army Medical Research and Development Command Institutional Review Board. RESULTS Performing the SPT from a chair significantly (P < .05) increased performance when compared to performing the SPT from the ground (5.4 ± 1.3 m versus 5.0 ± 1.4 m, respectively). Values for the two SPT variants were correlated (tau = 0.90). Performing the SDL using the hex-bar significantly increased the maximal weight lifted when compared to performing the SDL using paired dumbbells (86.9 ± 18.4 kg versus 83.1 ± 18.0 kg, respectively). Values for the two SDL variants were correlated (tau = 0.83). CONCLUSIONS Performing different variants of the SPT and SDL influenced the resulting score. Although these findings do not alter the administration or scoring of the OPAT, they do provide a valuable reference in the event of future inquiries regarding the development of the OPAT.

BACKGROUND AND AIM: Aerobic performance had been shown to decline during military deployment. Low levels of cardiorespiratory and muscular endurance may increase injury risk. We evaluated whether deployment-related declines in cardiorespiratory and muscular endurance increased injury risk. METHODS: The study population was all U.S. Army Soldiers (N= 6,080) who had completed the Army Physical Fitness Test (APFT) 90 days before and after deployment from 2016-2019. We defined injury as receiving an injury-related lost or limited-duty profile within 1-year post-deployment. We used mixed models to evaluate change in 2 mile-run time, 2-minute repetition maximum for pushups and sit-ups and overall APFT score. We used logistic regression models to evaluate relationships between changes in all scores on injury risk. We adjusted the models for pre-deployment event performance, prior injury, change in BMI, deployment duration, age and sex. RESULTS: 2-mile run time increased on average 16.6 seconds (95% CI: 12.6, 19.8) and overall APFT score declined 2.15 points (95% CI: -3.35, -0.94) after deployment. Pushups and sit-ups scores did not change after deployment. For every one minute increase in post-deployment run time, one point decrease in overall APFT score and one pushup decrease, the odds of receiving an injury-related profile increased by 6% (95% CI: 1.01, 1.11), 0.3% (95% CI: 0.995, 0.999) and 0.8% (95% CI: 0.986, 0.998), respectively. CONCLUSIONS We demonstrated that deployment-related declines in APFT-derived measures of physical fitness increased injury risk within 1-year post-deployment. Our findings suggest that maintaining pre-deployment cardiorespiratory and muscular endurance may be an effective strategy to attenuate injuries and lost duty time post-deployment. KEYWORDS: deployment, physical fitness, injuries Disclaimer: The opinions and assertions contained herein are the private views of the authors and are not to be construed as official or as reflecting the views of the U.S. Army or of the U.S. Department of Defense.

ABSTRACT Introduction This study characterized a sample of the first women to complete elite United States (US) military training. Methods Twelve female graduates of the US Army Ranger Course and one of the first Marine Corps Infantry Officers Course graduates participated in 3 d of laboratory testing including serum endocrine profiles, aerobic capacity, standing broad jump, common soldiering tasks, Army Combat Fitness Test, and body composition (dual-energy x-ray absorptiometry, three-dimensional body surface scans, and anthropometry). Results The women were 6 months to 4 yr postcourse graduation, 30 ± 6 yr (mean ± SD); height, 1.67 ± 0.07 m; body mass, 69.4 ± 8.2 kg; body mass index, 25.0 ± 2.3 kg·m−2. Dual-energy x-ray absorptiometry relative fat was 20.0% ± 2.0%; fat-free mass, 53.0 ± 5.9 kg; fat-free mass index, 20.0 ± 1.7 kg·m−2; bone mineral content, 2.75 ± 0.28 kg; bone mineral density, 1.24 ± 0.07 g·cm−2; aerobic capacity, 48.2 ± 4.8 mL·kg−1·min−1; total Army Combat Fitness Test score 505 ± 27; standing broad jump 2.0 ± 0.2 m; 123 kg casualty drag 0.70 ± 0.20 m·s−1, and 4 mile 47 kg ruck march 64 ± 6 min. All women were within normal healthy female range for circulating androgens. Physique from three-dimensional scan demonstrated greater circumferences at eight of the 11 sites compared with the standard military female. Conclusions These pioneering women possessed high strength and aerobic capacity, low %BF; high fat-free mass, fat-free mass index, and bone mass and density; and they were not virilized based on endocrine measures as compared with other reference groups. This group is larger in body size and leaner than the average Army woman. These elite physical performers seem most comparable to female competitive strength athletes.

Upon completion, participants will be able to describe the eating habits of Female Elite Warfighters.

Abstract Maintaining physical performance: the minimal dose of exercise needed to preserve endurance and strength over time, Spiering, BA, Mujika, I, Sharp, MA, and Foulis, SA. J Strength Cond Res 35(5): 1449–1458, 2021—Nearly every physically active person encounters periods in which the time available for exercise is limited (e.g., personal, family, or business conflicts). During such periods, the goal of physical training may be to simply maintain (rather than improve) physical performance. Similarly, certain special populations may desire to maintain performance for prolonged periods, namely athletes (during the competitive season and off-season) and military personnel (during deployment). The primary purpose of this brief, narrative review is to identify the minimal dose of exercise (i.e., frequency, volume, and intensity) needed to maintain physical performance over time. In general populations, endurance performance can be maintained for up to 15 weeks when training frequency is reduced to as little as 2 sessions per week or when exercise volume is reduced by 33–66% (as low as 13–26 minutes per session), as long as exercise intensity (exercising heart rate) is maintained. Strength and muscle size (at least in younger populations) can be maintained for up to 32 weeks with as little as 1 session of strength training per week and 1 set per exercise, as long as exercise intensity (relative load) is maintained; whereas, in older populations, maintaining muscle size may require up to 2 sessions per week and 2–3 sets per exercise, while maintaining exercise intensity. Insufficient data exists to make specific recommendations for athletes or military personnel. Our primary conclusion is that exercise intensity seems to be the key variable for maintaining physical performance over time, despite relatively large reductions in exercise frequency and volume.