BACKGROUND: Military operations occurring in austere environments result in declines of androgen status and physical performance, which has been associated with the severity of negative energy balance. However, whether negative consequences of military operations differ between environmental conditions has not been well described.
PURPOSE: To characterize energy expenditure, body composition, and androgen status during Marine mountain warfare summer and winter training.
METHODS: Sixty seven healthy US Marines taking part in summer (18 ± 3ºC, n = 46) or winter (2 ± 4ºC, n = 21) training at Marine Corps Mountain Warfare Training Center participated in this longitudinal observation study. Doubly labeled-water was used to determine energy expenditure throughout summer and winter training. Body composition (InBody 770) and blood draws were performed before and after 15 days of mountain warfare training. Data presented as mean ± SD.
RESULTS: Energy expenditure was 3782 ± 688 kcal/d during summer and 4596 ± 688 kcal/d during winter Marine mountain warfare training. Summer training resulted in a decline (P < 0.01) in body mass (-2.7 ± 1.5 kg), fat mass (-1.1 ± 1.0 kg), lean mass (-1.6 ± 1.3 kg), total body water (-1.2 ± 1.0 kg), and dry lean mass (-0.5 ± 0.4 kg). Winter training resulted in a decline (P < 0.01) in body mass (-2.2 ± 1.1 kg), lean mass (-1.7 ± 1.1 kg), total body water (-1.3 ± 0.8 kg), and dry lean mass (-0.4 ± 0.3 kg). There was no difference in fat mass (-0.5 ± 1.2 kg) following winter training. Following summer training a decline (P < 0.01) in IGF-1 (-28 ± 27 ng/mL), but not testosterone (36 ± 124 ng/dL) was observed, while in both IGF-1 (-51 ± 38 ng/mL) and testosterone (-111 ± 135 ng/dL) declined (P < 0.01) following winter training.
CONCLUSION: Findings from this investigation indicate that both summer and winter mountain warfare training result in declines in body mass and dry lean mass, while only winter training results in a decline in both circulating IGF-1 and testosterone.
This material is based on the work supported by DHP JPC-5/MOMRP; authors’ views not official U.S. Army or DoD policy.