Sex-Specific Lean Mass Changes during Marine Corps Officer Candidates School and Associations with Physical Health, Performance, and Military Readiness.

Abstract

Individuals participating in military training are subject to physical training that can affect body mass and composition in a manner that may be dependent on sex and relate to physical health and performance. This investigation compared changes in body composition between sexes during Marine Corps Officer Candidates School, and explored potential associations with physical health, performance, and military readiness outcomes. At the onset of training, 55 officer candidates ( n = 27 female) completed body composition analyses and 28 ( n = 11 female) completed posttesting. Two-way mixed measures analyses of variance compared changes over time between sexes, and Pearson or Spearman correlations examined associations among changes in body composition and performance outcomes. After training, lean mass ( P = 0.002, 7%) increased in female but not male candidates. Body fat percentage ( P = 0.013) decreased to a greater extent in female ( P < 0.001, -33%) than in male ( P < 0.001, -26%) candidates. Reductions in body mass and fat mass were similar between sexes. Change in body mass was negatively associated with change in physical fitness test score ( P = 0.038, r = -0.401), such that greater reductions in body mass would be associated with greater improvements in test score. Positive associations between change in body mass, body mass index, and lean mass ( P ≤ 0.040, r ≥ 0.414) with change in countermovement jump absolute force were observed. Increased lean mass was associated with reduced C-reactive protein concentration ( P = 0.004, ρ = -0.675). Reductions in fat mass and body mass as well as sex-specific changes in lean mass were demonstrated. Lean mass may also be beneficial for maintaining physical performance and health during military training.