Physical performance responses during 72 h of military operational stress

PURPOSE: To characterize the impact of prolonged work, underfeeding, and sleep deprivation (i.e., sustained operations; SUSOPS) on physical and occupational related performance during military operational stress. METHODS: Ten male soldiers were tested on days 1 (D1), 3 (D3), and 4 (D4) of a control and an experimental week that included prolonged physical work (total daily energy expenditure approximately 4,500 kcal x d(-1)), underfeeding (approximately 1,600 kcal x d(-1)), and sleep deprivation (approximately 2 h x d(-1)). Body composition was measured with dual-energy x-ray absorptiometry (DEXA). Ballistic power was assessed by 30 repetitive squat jumps and bench-press throws. Military-relevant occupational performance was evaluated with a 10-min box lift, obstacle course, grenade throw, rifle marksmanship, and a 25-min wall-build task. RESULTS: Fat-free mass (-2.3%) and fat mass (-7.3%) declined (P