Impact of United States marine corps recruit training on the stress response and menstrual function in female marine recruits

This study investigated the physiological stress response and menstrual cycle (MC) function in Marine recruits during United States Marine Corps Recruit Training at the Marine Corps Recruit Depot in San Diego, CA. Female recruits (n = 120) completed pre- and post-RT MC surveys. Saliva samples were collected at 6 timepoints (pre-RT, weeks 1, 4, 7, 10, post-RT) and analyzed for stress biomarkers. Urine samples were collected pre-RT, 5 days per week during RT, and post-RT to assess sex hormone metabolites. Linear mixed-effects models assessed time effects (p < 0.05). Pre-RT sAA levels were higher than weeks 4 (p < 0.001), 7 (p < 0.001), and 10 (p = 0.003). Week 1 sAA levels were greater than week 7 (p = 0.049) and post-RT sAA levels were greater than week 4 (p = 0.011), 7 (p < 0.001), and 10 (p = 0.046). Cortisol at weeks 1 (p = 0.004) and 4 (p < 0.001) was greater than week 10. Before RT, 85% reported regular MCs; during RT, 53% reported irregularity. Urine measures indicated 92% experienced MC disruption, 87.5% within the first cycle. Recruits experienced heightened stress early in RT but adapted as training progressed. Most recruits exhibited MC irregularities, with disruption occurring in the first cycle, indicating heightened hypothalamic-pituitary-ovarian axis sensitivity to military training stress.