Fight load index and body composition are most associated with combat fitness in female Marines

Influence of the Type of Physical Training on the Physical Fitness of Army Cadets

INTRODUCTION

Military Physical Training programs represent a constant challenge for the Armed Forces to improve body composition indices and physical fitness levels. This study aimed to verify the influence of the type of training on the physical fitness and body composition of army cadets, using 2 strategies: a sports program (Athletes group) and conventional physical training (Traditional group).

MATERIALS AND METHODS

This study involved new entrant male cadets who were selected for the Athletes group (n = 243, 19.08 ± 1.23 years) or the Traditional group (n = 356, 18.89 ± 0.97 years), with assessments occurring before and after the period of training (31.4 ± 3.9 weeks). Dual-energy X-ray absorptiometry was used to measure the bone mineral content (BMC), fat mass (FM), percentage of fat mass (%FM), and lean soft tissue (LST). The physical tests evaluated the 3,000 m run (RUN), 50 m swim (SWIM), pull-ups (PULL) on the horizontal bar, push-ups (PUSH) on the ground, and abdominal flexion (SITUP).

RESULTS

Time × group interaction effects were observed for BMC (P < .001), LST (P < .023), RUN (P < .001), PULL (P = .006), PUSH (P < .001), SITUP (P = .007), and SWIM (P < .001). A significant effect of time was noted for all variables analyzed in both groups, except %FM. The Athletes group achieved better results in body composition and in PULL, PUSH, RUN, and SWIM at baseline and after the training period. The Traditional group demonstrated higher relative changes (%) after the training period in the LST (P = .001), PULL (P < .001), PUSH (P < .001), SITUP (P < .004), and SWIM (P < .001) compared to the Athletes group.

CONCLUSION

Both physical training programs improved body composition and physical performance.

Unsupervised Machine Learning in Countermovement Jump and Isometric Mid-Thigh Pull Performance Produces Distinct Combat and Physical Fitness Clusters in Male and Female U.S. Marine Corps Recruits

INTRODUCTION

Several challenges face the U.S. Marine Corps (USMC) and other services in their efforts to design recruit training to augment warfighter mobility and resilience in both male and female recruits as part of an integrated model. Strength and power underpin many of the physical competencies required to meet the occupational demands one might face in military. As the military considers adopting force plate technology to assess indices of strength and power, an opportunity presents itself for the use of machine learning on large datasets to deduce the relevance of variables related to performance and injury risk. The primary aim of this study was to determine whether cluster analysis on baseline strength and power data derived from countermovement jump (CMJ) and isometric mid-thigh pull (IMTP) adequately partitions men and women entering recruit training into distinct performance clusters. The secondary aim of this study is then to assess the between-cluster frequencies of musculoskeletal injury (MSKI).

MATERIALS AND METHODS

Five hundred and sixty-five males (n = 386) and females (n = 179) at the Marine Corps Recruit Depots located at Parris Island and San Diego were enrolled in the study. Recruits performed CMJ and IMTP tests at the onset of training. Injury data were collected via medical chart review. Combat fitness test (CFT) and physical fitness test (PFT) results were provided to the study team by the USMC. A k-means cluster analysis was performed on CMJ relative peak power, IMTP relative peak force, and dynamic strength index. Independent sample t-tests and Cohen's d effect sizes assessed between-cluster differences in CFT and PFT performance. Differences in cumulative incidence of lower extremity %MSKIs were analyzed using Fisher's exact test. Relative risk and 95% confidence intervals (CIs) were also calculated.

RESULTS

The overall effects of cluster designation on CMJ and IMTP outcomes ranged from moderate (relative peak power: d = -0.68, 95% CI, -0.85 to -0.51) to large (relative peak force: d = -1.69, 95% CI, -1.88 to -1.49; dynamic strength index: d = 1.20, 95% CI, 1.02-1.38), indicating acceptable k-means cluster partitioning. Independent sample t-tests revealed that both men and women in cluster 2 (C2) significantly outperformed those in cluster 1 (C1) in all events of the CFT and PFT (P < .05). The overall and within-gender effect of cluster designation on both CFT and PFT performance ranged from small (d > 0.2) to moderate (d > 0.5). Men in C2, the high-performing cluster, demonstrated a significantly lower incidence of ankle MSKI (P = .04, RR = 0.2, 95% CI, 0.1-1.0). No other between-cluster differences in MSKI were statistically significant.

CONCLUSIONS

Our results indicate that strength and power metrics derived from force plate tests effectively partition USMC male and female recruits into distinct performance clusters with relevance to tactical and physical fitness using k-means clustering. These data support the potential for expanded use of force plates in assessing readiness in a cohort of men and women entering USMC recruit training. The ability to pre-emptively identify high and low performers in the CFT and PFT can aid in leadership developing frameworks for tailoring training to enhance combat and physical fitness with benchmark values of strength and power.

Anthropomorphic and Physical Fitness Characteristics of United States Air Force Basic Military Training: Special Warfare Versus Nonspecial Warfare Recruits, Fiscal Year 2019-2023

INTRODUCTION

Each year, thousands of individuals enlist in the Department of the Air Force (DAF), with some seeking to become DAF Special Warfare (SW) candidates. This study aimed to compare the anthropomorphic and physical fitness characteristics between these groups during fiscal years (FYs) 2019-2023.

METHODS

 The sample includes male candidates below the age of 30 who attended the DAF basic military training (BMT) from FY2019 to 2023 (N = 119,415). Initial physical fitness testing was conducted during week 1 of BMT. Physical fitness results, height, weight, and body mass index (BMI) were compared between the two cohorts. A two-way analysis of variance was performed to analyze the effects of group (SW and non-SW) and FY on mean anthropomorphic and physical fitness test variables. Dependent variables were evaluated for homogeneity of variance using Levene's test and for normality using the Shapiro-Wilk test. The Tukey-Kramer test was employed for post hoc analyses with a threshold for statistical significance of α < 0.05.

RESULTS

 The cohort of SW recruits displayed superior physical fitness results across all FYs (p < 0.001) with the exception of FY2021. They were significantly taller and heavier, and had a higher BMI when compared to non-SW DAF BMT recruits (p < 0.001). Mean values for maximum push-ups and sit-ups for SW recruits were significantly lower in FY2021 (p < 0.001) and not significantly different from non-SW recruits. Additionally, run times for both SW- and non-SW-bound recruits during FY2022 and FY2023 were significantly slower than previous years.

CONCLUSIONS

 These findings can be used to establish a baseline for anthropometric and physical fitness profiles of incoming SW and non-SW DAF BMT recruits that may inform clinicians, human performance professionals, and military training leaders with information necessary to guide future research and physical fitness policy.

Musculoskeletal Injuries, Exercise Behaviors, and Reproductive Health Are Related to Physical Fitness of Female First-Responders and Health Care Providers

Introduction

Musculoskeletal injuries (MSKi) are the most common injury type experienced by first-responders and health care providers (HCPs), making them a significant threat to physical and mental well-being. Female reproductive health and injury history has been related to physical fitness in female members of the Canadian Armed Forces. This relationship has not been explored in Canadian protective services personnel (first-responders) or HCPs.

Methods

Fifty-seven females employed as firefighters, paramedics, law enforcements, or HCPs completed a physical fitness protocol to assess the following: (1) muscular power (standing long jump and medicine ball throw), (2) muscular strength (4 repetition maximum (4RM) back squats and bench press), (3) muscular endurance (Biering-Sorenson test, single-leg wall sit, and push-ups), (4) flexibility (sit-and-reach), and (5) aerobic capacity (graded treadmill VO2max test). Spearman rho correlation analyses were applied to descriptive analysis, independent-samples t-test, one-way ANCOVA (adjusted by age), and chi-square test. Spearman rho correlation analyses were used to compare physical fitness results for female reproductive health history (e.g., parity status), previous MSKi, and physical activity behaviors (e.g., sports participation). A p value of <0.05 is considered significant.

Results

History of childbirth, body composition, and exercise behaviors were related to physical fitness (i.e., standing long jump, Biering-Sorenson test, bench press, and back squat) in law enforcement, firefighting, paramedicine, and health care personnel.

Conclusions

Physical training programs aimed at supporting parous first-responders or HCPs should emphasize lower body power, lower body strength, and upper body strength.

Body composition as a marker of performance and health in military personnel

Introduction

Body composition standards are set to ensure operational readiness in active-duty military personnel. To meet body composition standards, some individuals, however, may engage in unhealthy weight control behaviors (i.e., weight cycling and disordered eating). The objectives of this review are to: (1) evaluate the evidence regarding body composition and the associations to physical and military specific performance; (2) discuss body composition and potential health consequences; and (3) examine the evidence of weight cycling and disordered eating behaviors in military personnel for weight control.

Methods

A systematic search to identify peer-reviewed research articles was conducted in PubMed on 2/20/2023 using Medical Subject Headings (MeSH) including but not limited to "Military Personnel", "Tactical Athlete", "Weight Loss", "Body Composition", and "Weight Cycling".

Results

A total of 225 research articles were identified. The list was narrowed down to articles from the last 20 years (2003-2023) in military personnel. Only studies in which percent body fat was directly measured were included resulting in 17 research articles for this review.

Discussion

Evidence-based research is limited on the relationship between body composition and operational readiness. Weight cycling and disordered eating behaviors also has been reported for weight control, yet additional research is needed. Specifically, future research should focus on female service members, racial and ethnic differences, age, and postpartum status and include other service branches (i.e., Air Force and Navy). A comprehensive survey on weight cycling, disordered eating, and weight management would be valuable to determine the prevalence and extent of this issue. This information along with performance data would guide policy makers on the relevance and appropriateness of existing body composition standards.

Decreased Percent Body Fat but Not Body Mass is Associated with Better Performance on Combat Fitness Test in Male and Female Marines

ABSTRACT

Pletcher, ER, Lovalekar, M, Coleman, LC, Beals, K, Nindl, BC, and Allison, KF. Decreased percent body fat but not body mass is associated with better performance on the Marine Corps Combat Fitness Test. J Strength Cond Res 37(4): 887-893, 2023-The military uses a variety of physical fitness tests to assess physical readiness. The Marine Corps designed the Combat Fitness Test (CFT) to emphasize functional fitness related to operational demands. The purpose of this study was to investigate the association between body mass (BM), fat free mass (FFM), and percent body fat (BF%) measured via air displacement plethysmography with CFT performance in male and female marines. Two-hundred 10 male (22.4 ± 2.6 years) and 84 female (22.6 ± 2.8 years) marines were grouped into quintiles according to BM (in kilograms), FFM (in kilograms), and BF%. Kruskal-Wallis test or 1-way analysis of variance were used to determine if significant differences in CFT total and component scores existed between the groups of subjects classified into quintiles of BM, FFM, and BF%. No significant differences in CFT scores were observed between BM quintile in either men or women. No significant differences in CFT scores were observed between FFM quintiles in men. Total CFT score ( p = 0.002), movement to contact (MTC; p = 0.014), maneuver under fire (MANUF; p = 0.008), and ammunition lift (AL; p = 0.014) were all significantly different among FFM quintiles in women. Total CFT score ( p = 0.007), MTC ( p = 0.001), and MANUF ( p = 0.022) were significantly different among BF% quintiles in men. Total CFT score ( p = 0.008), MTC ( p = 0.033), and AL ( p = 0.016) were significantly different among BF% quintiles in women. Male and female marines in the quintile with lowest BF% had better CFT scores than those in higher quintiles. Targeted physical training and nutrition considerations to optimize BF% may help improve military task performance.

Military Body Composition Standards and Physical Performance: Historical Perspectives and Future Directions

ABSTRACT

Harty, PS, Friedl, KE, Nindl, BC, Harry, JR, Vellers, HL, and Tinsley, GM. Military body composition standards and physical performance: historical perspectives and future directions. J Strength Cond Res 36(12): 3551-3561, 2022-US military physique and body composition standards have been formally used for more than 100 years. These metrics promote appropriate physical fitness, trim appearance, and long-term health habits in soldiers, although many specific aspects of these standards have evolved as evidence-based changes have emerged. Body composition variables have been shown to be related to many physical performance outcomes including aerobic capacity, muscular endurance, strength and power production, and specialized occupational tasks involving heavy lifting and load carriage. Although all these attributes are relevant, individuals seeking to improve military performance should consider emphasizing strength, hypertrophy, and power production as primary training goals, as these traits appear vital to success in the new Army Combat Fitness Test introduced in 2020. This fundamental change in physical training may require an adjustment in body composition standards and methods of measurement as physique changes in modern male and female soldiers. Current research in the field of digital anthropometry (i.e., 3-D body scanning) has the potential to dramatically improve performance prediction algorithms and potentially could be used to inform training interventions. Similarly, height-adjusted body composition metrics such as fat-free mass index might serve to identify normal weight personnel with inadequate muscle mass, allowing for effective targeted nutritional and training interventions. This review provides an overview of the origin and evolution of current US military body composition standards in relation to military physical readiness, summarizes current evidence relating body composition parameters to aspects of physical performance, and discusses issues relevant to the emerging modern male and female warrior.

Anthropometrics and body composition predict performance during a simulated direct-fire engagement

This study determined anthropometric and body composition predictors of performance during a simulated direct-fire engagement. Healthy subjects (N = 33, age = 25.7 ± 7.0 yr) underwent anthropometric and body composition assessments before completing a simulated direct-fire engagement - consisting of marksmanship with cognitive workload assessment and a fire-and-move drill (16 × 6-m sprints) while wearing combat load. Susceptibility to enemy fire was modelled on sprint duration. Partial correlations and multiple linear regressions established the relationships between predictors and performance outcomes, controlling for age and sex. Significance was p ≤ 0.05. Higher percent body fat, fat mass, fight load index predicted greater susceptibility to enemy fire (r = 0.40 to 0.42) and lower cognitive performance (r= -0.45 to -0.49). Higher BMI also predicted lower cognitive performance (r= -0.49). Shorter stature/hand length predicted higher marksmanship accuracy (r= -0.40), while higher fat-free mass/fat-free mass index predicted slower reaction times (r = 0.36-0.41). These data suggest anthropometric and body composition measures modulate combat effectiveness and reinforce body composition standards in military organisations. Practitioner summary: This study identified field-expedient anthropometric and body composition predictors of a simulated direct-fire engagement that evaluated survivability (i.e. susceptibility to enemy fire) and lethality (i.e. marksmanship, cognitive performance) outcomes. Our findings suggest that anthropometric and body composition measures may play a role in soldier survivability and lethality during simulated direct-fire engagements.

Lower-body muscular power and exercise tolerance predict susceptibility to enemy fire during a tactical combat movement simulation

This study examined if field-expedient physical fitness/performance assessments predicted performance during a simulated direct-fire engagement. Healthy subjects (n = 33, age = 25.7 ± 7.0 years) completed upper- and lower-body strength and power assessments and a 3-min all-out running test to determine critical velocity. Subjects completed a simulated direct-fire engagement that consisted of marksmanship with cognitive workload assessment and a fire-and-move drill (16 × 6-m sprints) while wearing a combat load. Susceptibility to enemy fire was modelled on average sprint duration during the fire-and-move drill. Stepwise linear regression identified predictors for the performance during the simulated direct-fire engagement. Critical velocity (β = -0.30, p < 0.01) and standing broad jump (β = -0.67, p < 0.001) predicted susceptibility to enemy fire (R² = 0.74, p < 0.001). All predictors demonstrated poor relationships with marksmanship accuracy and cognitive performance. These data demonstrate the importance of exercise tolerance and lower-body power during simulated direct-fire engagements and provide potential targets for interventions to monitor and enhance performance and support soldier survivability. Practitioner Summary: This study identified field-expedient physical fitness/performance predictors of a simulated direct-fire engagement which evaluated susceptibility to enemy fire, marksmanship, and cognitive performance. Our findings suggest that high-intensity exercise tolerance and lower-body power are key determinants of performance that predicted susceptibility to enemy fire.

Unsupervised Clustering Techniques Identify Movement Strategies in the Countermovement Jump Associated With Musculoskeletal Injury Risk During US Marine Corps Officer Candidates School

Musculoskeletal injuries (MSKI) are a significant burden on the military healthcare system. Movement strategies, genetics, and fitness level have been identified as potential contributors to MSKI risk. Screening measures associated with MSKI risk are emerging, including novel technologies, such as markerless motion capture (mMoCap) and force plates (FP) and allow for field expedient measures in dynamic military settings. The aim of the current study was to evaluate movement strategies (i.e., describe variables) of the countermovement jump (CMJ) in Marine officer candidates (MOCs) via mMoCap and FP technology by clustering variables to create distinct movement strategies associated with MSKI sustained during Officer Candidates School (OCS). 728 MOCs were tested and 668 MOCs (Male MOCs = 547, Female MOCs = 121) were used for analysis. MOCs performed 3 maximal CMJs in a mMoCap space with FP embedded into the system. De-identified MSKI data was acquired from internal OCS reports for those who presented to the OCS Physical Therapy department for MSKI treatment during the 10 weeks of OCS training. Three distinct clusters were formed with variables relating to CMJ kinetics and kinematics from the mMoCap and FPs. Proportions of MOCs with a lower extremity and torso MSKI across clusters were significantly different (p < 0.001), with the high-risk cluster having the highest proportions (30.5%), followed by moderate-risk cluster (22.5%) and low-risk cluster (13.8%). Kinetics, including braking rate of force development (BRFD), braking net impulse and propulsive net impulse, were higher in low-risk cluster compared to the high-risk cluster (p < 0.001). Lesser degrees of flexion and shorter CMJ phase durations (braking phase and propulsive phase) were observed in low-risk cluster compared to both moderate-risk and high-risk clusters. Male MOCs were distributed equally across clusters while female MOCs were primarily distributed in the high-risk cluster. Movement strategies (i.e., clusters), as quantified by mMoCap and FPs, were successfully described with MOCs MSKI risk proportions between clusters. These results provide actionable thresholds of key performance indicators for practitioners to use for screening measures in classifying greater MSKI risk. These tools may add value in creating modifiable strength and conditioning training programs before or during military training.

Body mass index and aerobic capacity: The key variables for good performance in soldiers

Body composition, leg power and aerobic capacity have been shown to be related to performance, although their combined influence in a training task under load carriage in soldiers is still unknown. In this study, the influence of aerobic capacity, body composition and leg strength on performance during an obstacle test with and without combat equipment carriage was analysed. Forty males belonging to the Spanish Army participated in this study. The time needed to complete an obstacle course with and without load, aerobic capacity (20-m shuttle run test), leg power (squat jumps) and body composition variables (body mass index [BMI], fat mass and lean mass) were tested to determine the best predictors of performance. The results indicated that the best predictors of obstacle course performance with and without load carriage are VO_2max and BMI. The jump height was not a significant factor in the model. In conclusion, BMI and VO_2max are predictors of the obstacle test time with and without load carriage, so it is recommended that both variables are included as criteria for enrolment in the military army to guarantee army members exhibit the highest obstacle course performance possible. HighlightThe VO_2max and BMI are the best predictors of an obstacle course performance with/without load carriage.The jump height was not a significant performance factor.The VO_2max and BMI are recommended as enrolment criteria for military army.