Anthropometrics and Body Composition Predict Physical Performance and Selection to Attend Special Forces Training in United States Army Soldiers

Abstract

Introduction Anthropometrics and body composition characteristics differentiate many types of athletes and are related to performance on fitness tests and tasks in military personnel. Soldiers competing to enter elite units must demonstrate physical fitness and operational competence across multiple events. Therefore, this study determined whether anthropometrics and body composition predicted physical performance and selection for special forces training among soldiers attending the rigorous Special Forces Assessment and Selection (SFAS) course. Materials and Methods Soldiers attending the SFAS course between May 2015 and March 2017 were enrolled in a longitudinal, observational study. Anthropometrics (height, body mass, and body mass index [BMI]; n = 795) and body composition measured by dual-energy X-ray absorptiometry (percentage body fat, fat mass, lean mass, bone mineral content [BMC], and bone mineral density [BMD]; n = 117) were assessed before the course start. Associations with physical performance were determined with correlation coefficients. Associations with selection were determined with analyses of variance and t-tests; effect sizes were calculated as Cohen’s d. The U.S. Army Research Institute of Environmental Medicine Institutional Review Board (IRB) initially approved this study, and the U.S. Army Medical Research and Development Command IRB approved the continuing review. Results Lower percentage body fat and fat mass predicted better performance on all assessments: Army Physical Fitness Test (APFT), pull-ups, SFAS run, loaded road march, obstacle course, and land navigation (P ≤ .05). Higher lean mass predicted better performance on the loaded road march (P ≤ .05). Lower body mass and BMI predicted better performance on APFT, pull-ups, run, and obstacle course; higher body mass and BMI predicted better performance on the loaded road march (P ≤ .05). Shorter stature predicted better performance on push-ups (APFT) and pull-ups; taller stature predicted better performance on SFAS run and loaded road march (P ≤ .05). On average, the selected soldiers were taller (179.0 ± 6.6 vs. 176.7 ± 6.7 cm), had higher body mass (85.8 ± 8.8 vs. 82.1 ± 9.6 kg), BMI (26.8 ± 2.2 vs. 26.3 ± 2.6 kg/m2), lean mass (67.2 ± 7.3 vs. 61.9 ± 7.6 kg), BMC (3.47 ± 0.40 vs. 3.29 ± 0.56 kg), and BMD (1.34 ± 0.10 vs. 1.28 ± 0.10 g/cm2), and lower percentage body fat (17.3 ± 3.4 vs. 20.1 ± 4.5%) and fat mass (14.2 ± 3.7 vs. 15.8 ± 4.4 kg) (P ≤ .05). Effect sizes were largest for lean mass (Cohen’s d = 0.71) and percentage body fat (d = 0.70), followed by BMD (d = 0.60), body mass (d = 0.40), fat mass (d = 0.39), BMC (d = 0.37), height (d = 0.35), and BMI (d = 0.21). Body mass adjustment attenuated associations between height and selection. Conclusions Anthropometrics and body composition are predictors of physical performance and SFAS success. Since these measures are modifiable (excluding height), they may be the focus of intervention studies aiming to improve performance in arduous military training courses, sports that require competition in multiple events, and occupations that have varied physical demands, such as firefighting, law enforcement, and construction.

Body Composition, Eicosapentaenoic Acid, and Vitamin D are Associated with Army Combat Fitness Test Performance

“…Although our hypothesis was related to LBM, we found that lower %BF was strongly correlated with higher scores on all ACFT events, except the PLK. Our findings are consistent with military studies that report lower %BF is associated with better 2MR [ 7 , 8 ] and push-up scores [ 8 ]. Despite the Army’s shift to the ACFT that is more focused on strength, power, speed, and agility; our investigation indicates that %BF has proven to be an important contributor to success on events that assess these physical domains, and therefore, performance of combat-relevant tasks.…”

“…While LBM was correlated with HRPU scores, controlling for %BF attenuated the association between LBM and HRPU performance. Similarly, Farina et al [ 8 ] found that lower %BF predicted better performance on the push-up event, whereas LBM did not.…”

“…It is widely established that specific body composition characteristics are related to performance on various fitness and combat tasks in military personnel [ 6 ]. For example, previous research has identified lower body fat percentage (%BF) as a key physical trait associated with improved performance on the APFT [ 7 , 8 ] and other military relevant tasks [ 8 ], whereas lean body mass (LBM) is not associated with overall APFT performance. This concept is reflected within the Army body composition standards which are largely focused on %BF.…”

Perfil de Composición Corporal en Militares Élite Chilenos

“…Una reciente revisión de la literatura (Farina et al, 2021) reveló que la composición corporal es un predictor del rendimiento físico que puede ser modificado, de esta manera; y es así que una buena composición corporal permite una mejor preparación para las exigencias de los cursos militares que requieren de altas demandas físicas. Al comparar la talla de soldados de distintos ejércitos se aprecia que los soldados serbios (180,2 cm), finlandeses (180,0 cm) y montenegrinos (181,7 cm) serían los más altos, mientras que los canadienses (178,0 cm), los belgas (177,5 cm), los estadounidenses (176,0 cm) y los turcos (173,0 cm) son los más bajos (Spalevic et al, 2021).…”

Initial military training modulates serum fatty acid and amino acid metabolites

“…The observed changes indicate that the current US Army IMT environment promotes anabolism and supports positive adaptations to physical training in new military recruits independent of dietary intake. These findings are important due to the association between body composition and physical performance (Farina et al, 2021) as well as injury risk (Anderson et al, 2015; Jones et al, 2017) in various military populations.…”