Characterization of Sleep and Body Composition Changes During Ranger Training

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Abstract
Fifteen U.S. Army soldiers were outfitted with wrist-worn, solid-state activity monitors and had body weight and physical measurements taken while undergoing a 58-day, four-phase ranger training course. Records from the activity monitors indicated that the average daily sleep obtained by the soldiers was 3.2 hr. Average daily sleep by training phase was: Fort Benning - 3.5 hr, mountain-3.9 hr, swamp-2.6 hr, and desert-3.0 hr. Average weight at the first weigh-in was 178.2 lb with a bodyfat composition of 14.7%. At the final weigh-in, average weight was 169.7 lb; bodyfat, however, was essentially the same at 14.3%. This suggests that the weight loss may be due to a reduction in lean body mass, indicative of the stresses placed on the soldiers during training. The implications of these findings are discussed.