Heat strain in protective clothing following hot-wet or hot-dry heat acclimation.

The purpose of the present study was to compare the heat strain while wearing nuclear, biological, and chemical (NBC) protective clothing following a hot-wet (HW) or hot-dry (HD) heat acclimation protocol. Twenty-two males were assigned to groups HW (n = 7), HD (n = 8), or control (C, n = 7). Subjects were evaluated during continuous treadmill walking while wearing lightweight combat clothing and during intermittent exercise while wearing the NBC protective clothing. While wearing Combat clothing, greater decreases in rectal temperature (Tre), mean skin temperature (Tsk), and heart rate were observed for both acclimation groups. For the NBC clothing trials, lower Tre, Tsk, and heart rates were observed only for group HW. The time required for Tre to increase 1.0 degrees C and 1.5 degrees C was significantly delayed for groups HW and HD. Sweat evaporation increased for HW, whereas no change was found for HD. The most significant changes in Tre, Tsk, and heart rate while wearing the NBC protective clothing occur following heat acclimation that involves wearing the clothing during exercise.