Physical performance responses during 72 h of military operational stress.
OBJECTIVE
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.


CONCLUSIONS
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.
Nindl
Bradley C
BC
Military Performance Division, U.S. Army Research Institute of Environmental Medicine, Natick, MA 01760, USA. bradley.nindl@na.amedd.army.mil
Leone
Cara D
CD
Tharion
William J
WJ
Johnson
Richard F
RF
Castellani
John W
JW
Patton
John F
JF
Montain
Scott J
SJ
D000222:Adaptation, Physiological; D000328:Adult; D000704:Analysis of Variance; D001823:Body Composition; D001835:Body Weight; D006801:Humans; D008297:Male; D008889:Military Personnel; D009790:Occupations; D010807:Physical Endurance / Q000502:physiology*; D005082:Physical Exertion; D011336:Probability; D012016:Reference Values; D018570:Risk Assessment; D012494:Sampling Studies; D013312:Stress, Physiological / Q000503:physiopathology*; D013647:Task Performance and Analysis