Upper body sweat mapping provides evidence of relative sweat redistribution towards the periphery following hot-dry heat acclimation

Abstract

Purpose : Produce a detailed upper-body sweat map and evaluate changes in gross and regional sweating rates (RSR) and distribution following heat acclimation (HA). Methods : Six males (25 ± 4 yrs) completed six consecutive HA days (45°C, 20% rh) requiring 90 minutes intermittent exercise to maintain a 1.4°C rectal temperature (Tre) rise. Pre- and post-HA upper-body RSR were measured at 55% (Intensity-1; I1) and 75% VO2 max (Intensity-2; I2) using a modified absorbent technique. Results : From day one to six of HA, work rate increased (n.s.), heart rate, Tre, and skin temperature were similar, and gross sweat loss (GSL) increased (P < 0.001). During pre and post-HA experiments, relative workloads were similar (Pre-I1 54 ± 3, Post-I1 57 ± 5%VO2max; Pre-I2 73 ± 4, Post-I2 76 ± 7%VO2max). Post-HA GSL was significantly higher (Pre 449 ± 90 g.m−2 h−1, Post 546 g.m−2 h−1; P < 0.01). Highest RSR were observed on the central back both pre and post-HA at I1 (pre 854 ± 269 post 1178 ± 402g.m−2 h−1) and I2 (pre 1221 ± 351 post 1772 ± 396 g.m−2 h−1). Absolute RSR increased significantly in 12 (I1) to 14 (I2) of the 17 regions. Ratio data indicated significant post-HA relative RSR redistribution, with decreased relative contributions to whole-body sweating on the back, chest staying the same and arms increasing. Conclusions : Hot-dry HA significantly increased GSL in aerobically trained males at I2. Absolute RSR significantly increased in I1 and I2, with a preferential relative redistribution towards the periphery of the upper-body.