Physiological and metabolic responses to winter warfare training in special operations soldiers

Abstract

U.S. Army Special Forces (SF) personnel undergo intensive training for unconventional warfare, which includes winter warfare training (WWT). WWT is a rigorous multi-day training exercise including mountaineering, skiing, and tactical movements in a multi-stressor environment that simultaneously exposes operators to cold and varying altitudes. This study objectively quantified the physiological and metabolic responses of WWT. Twelve experienced SF soldiers (age: 33±1 yr; mass: 85.5±1.9 kg; body fat: 16.2±1%; VO2max: 45.3±1.6 mL/kg/min) completed study measures at baseline, and pre- post-WWT lasting 5 and 7 days. Salivary testosterone, cortisol, dehydroepiandrosterone (DHEA), and alpha-amylase were assessed via immunoassay. The Short Recovery and Stress Scale was administered to evaluate perceived recovery and stress. Urine specific gravity was assessed to monitor hydration status. Accelerometry and heart rate monitoring estimated daily physical activity intensity, workload (mileage from step count), and total daily energy expenditure throughout WWT. Daily workload was approximately 12 miles per day and soldiers expended 5,265-7,094 kcal/day or 85 kcal/kg/day and slept 5.4-10.0 hours per night. Overall, salivary testosterone and DHEA progressively declined throughout the study, while cortisol and alpha-amylase increased. Post-WWT urine specific gravity was elevated (dehydrated) compared to pre-WWT. Self-reported recovery decreased from pre-WWT to post-WWT but overall was quite high; inversely, perceived stress increased but overall was quite low throughout evolutions. Findings suggest WWT elicits high metabolic demand and physiological strain yet perception of stress is low, and subjective recovery is high in experienced SF soldiers.