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Physical performance responses during 72 h of military operational stress
Bradley C Nindl1, Cara D Leone, William J Tharion
1Military Performance Division, U.S. Army Research Institute of Environmental Medicine, Natick, MA 01760, USA. bradley.nindl@na.amedd.army.mil
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 = 0.05) during SUSOPS. Squat-jump mean power (-9%) and total work (-15%) declined (P = 0.05) during SUSOPS. Bench-press power output, grenade throw, and marksmanship for pop-up targets were not affected. Obstacle course and box-lift performances were lower (P = 0.05) on D3 but showed some recovery on D4. Wall building was approximately 25% lower (P = 0.05) during SUSOPS.
Conclusion:
Decrements in performance during SUSOPS are primarily restricted to tasks that recruit muscles that are over-utilized without adequate recovery. General military skill tasks and occupational physical performance tasks are fairly well maintained.
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