title: Physiological consequences of U.S. Army Ranger training.
abstract: OBJECTIVE
  Soldiers are expected to maintain a high degree of physical readiness as operational demands can severely degrade performance capabilities. This study examined the physiological consequences of U.S. Army Ranger training on strength, power, body composition, and somatotrophic hormones.
  
  
  METHODS
  In an intensive 8-wk military training course that included an average daily energy deficit of 1000 kcal.d, lower-body power output, maximal lifting strength, body composition, and serum concentrations of several somatotrophic hormones were measured in 50 male soldiers (24.6 +/- 4.4 y; 176.1 +/- 7.8 cm; 78.4 +/- 8.7 kg; 14.7 +/- 4.2% body fat) before and after the course.
  
  
  RESULTS
  Vertical jump height (-16%), explosive power output (-21%), maximal lifting strength. (-20%), body mass (-13%), fat-free mass (-6%), and fat mass (-50%) declined (P < 0.05) after the training course. Circulating total testosterone and insulin-like growth factor-I (IGF-I) experienced significant (P < 0.05) declines, and cortisol was significantly increased. Lower-body power output, but not maximal lifting strength, correlated with changes in fat-free mass. IGF-I and cortisol, but not total testosterone, were correlated with losses of tissue mass.
  
  
  CONCLUSIONS
  Lower-body power output, estimated from vertical jump height and body mass, is a sensitive and field expedient measure that can be used to assess the influence of caloric deficit on physical performance after 8 wk of U.S. Army Ranger training. With severe weight loss (>or=13% of body mass), IGF-I and cortisol correlate more closely with soft-tissue tissue adaptations than does testosterone.
authors.affiliation: Military Performance, 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: Brian R
authors.initials: BR
authors.lastname: Barnes
authors.forename: Joseph A
authors.initials: JA
authors.lastname: Alemany
authors.forename: Peter N
authors.initials: PN
authors.lastname: Frykman
authors.forename: Ronald L
authors.initials: RL
authors.lastname: Shippee
authors.forename: Karl E
authors.initials: KE
authors.lastname: Friedl
mesh_terms: D000328:Adult; D005080:Exercise Test; D013006:Growth Hormone / Q000032:analysis / Q000378:metabolism; D006801:Humans; D008297:Male; D008889:Military Personnel; D010809:Physical Fitness / Q000502:physiology*; D013647:Task Performance and Analysis; D014481:United States; D015431:Weight Loss
chemical_list: D013006:Growth Hormone