Physiological consequences of U.S. Army Ranger training.

PURPOSE: 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. CONCLUSION: 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.

Novel nutritional immune formula maintains host defense mechanisms.

Military combat and training stress induce immune changes that increase the risk of infection and ultimately influence soldiers' performance and readiness. Strenuous military training/assessment provides a uniform stress and the opportunity to evaluate nutritional strategies to minimize stress-induced immune changes that predispose soldiers to infection. Immunological changes and effects of a novel nutritional immune formula (NNIF) were examined prospectively in a double-blind, controlled study of 200 soldiers attending Special Forces Assessment and Selection School. Immune function was measured by skin delayed-type hypersensitivity, lymphocyte phenotyping, mitogenic proliferative responses, and granulocyte function. Approximately 50% of soldiers completed the study (control, n = 57; NNIF, n = 50). Several stress-induced lymphocyte changes were observed (decreased mitogen-induced proliferation, T and total lymphocytes, and interferon-gamma-producing lymphocytes and increased percentage of neutrophils). NNIF modified several changes, including delayed-type hypersensitivity responses (NNIF, 78%; control, 59%; p < 0.05), increased proportions of helper T cells, activation of B cells, enhanced neutrophil phagocytosis, and attenuation of declines in certain functional subpopulations (i.e., cytotoxic/ suppressor lymphocytes). Soldiers who consumed NNIF experienced less stress-induced immune impairment, thereby lowering the risk of infection.