title: Physical performance responses during 72 h of military operational stress.
abstract: 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.
authors.affiliation: Military Performance Division, U.S. Army Research Institute of Environmental Medicine, Natick, MA 01760, USA. bradley.nindl@na.amedd.army.mil
authors.forename: Bradley C
authors.initials: BC
authors.lastname: Nindl
authors.forename: Cara D
authors.initials: CD
authors.lastname: Leone
authors.forename: William J
authors.initials: WJ
authors.lastname: Tharion
authors.forename: Richard F
authors.initials: RF
authors.lastname: Johnson
authors.forename: John W
authors.initials: JW
authors.lastname: Castellani
authors.forename: John F
authors.initials: JF
authors.lastname: Patton
authors.forename: Scott J
authors.initials: SJ
authors.lastname: Montain
mesh_terms: 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