Body Sweat Mapping of Untrained Males during Exercise-Induced Hyperthermia

Abstract

Aerobic training increases gross and regional sweating rates (RSR) allowing improved evaporative heat loss. Variation in RSR are widely recognized, but limited RSR data and implications for thermoregulation are available in untrained individuals. PURPOSE: Our aim was to investigate RSR and distribution at 35 sites in young, untrained males (UT) versus endurance-trained male athletes (TR) during exercise-induced hyperthermia in a moderate environment. METHODS: Six young, healthy, untrained males (22 ± 3 yrs, VO2max 42.7 ± 7.2 ml.kg-1.min-1) and nine aerobically trained male athletes (23 ± 3 yrs, VO2max 70.2 ± 13 ml.kg-1.min-1) ran for 60 minutes in 25.6 ± 4.5°C, 48.5 ± 0.5% relative humidity, and a 1 m.s-1 air velocity. RSR were measured at two exercise intensities (I1, 60% VO2max; I2, 75% VO2max) using a modified absorbent technique. RESULTS: Core temperature was similar between groups at all stages (P>0.05). GSL was significantly higher in TR versus UT at I1 and I2 (I1: TR 365 ± 84, UT 157 ± 66 g.m-2.h-1, P<0.001; I2 TR 657 ± 119, UT 311 ± 93 g.m-2.h-1, p<0.001), reflecting a significantly higher absolute work rate in TR versus UT (p<0.01). Absolute RSR were significantly higher in TR versus UT at 28 of 35 regions at I1 and 31 out of 35 regions at I2. Highest RSR were observed on the central mid back in both groups (I1 TR 797 ± 250, UT 277 ± 120 g.m-2.h-1; I2 TR 1139 ± 364, UT 365 ± 148 g.m-2.h-1), with lowest values on the palms in TR (I1 98 ± 58, I2 126 ± 53, g.m-2.h-1) and anterior upper arms in UT (I1 33 ± 24, I2 71 ±30 g.m-2.h-1). Both groups showed a medial to lateral decrease in RSR on the posterior torso, and proximal to distal increase on the arms. Normalized ratio values were significantly different between groups at 4 and 6 sites out of 35 at I1 and I2, respectively, none of which were significant following Bonferroni correction. No correlation was observed between RSR and local skin temperature in either group. CONCLUSIONS: These data provide the most detailed exercise-induced RSR for untrained males, showing large RSR variation. Despite significant differences in GSL and absolute RSR, normalized data suggest no significant differences in distribution of sweat between groups. Male athletes demonstrated superior thermoregulation, with similar Tcore and Tsk values despite a higher absolute workload. Funded by the Adidas Innovation Team.