The effect of change in skin temperature due to evaporative cooling on sweating response during exercise.

The purpose of this study was to investigate whether there are any effects of skin temperature changes on sweating response in the first few minutes of mild exercise. Six healthy males performed a bicycle exercise at 100 W (50 rpm) for 30 min under an ambient temperature of 23 degrees C (40% RH). Esophageal temperature (Tes), mean skin temperature (Tsk), local skin temperature at the lower left scapula (Tsl), local sweating rate (Msw) and cutaneous blood flow by laser-Doppler flowmetry (LDF) were measured continuously. Although Tsl decreased markedly just after the onset of sweating, Tsk did not change. Msw did not increase constantly in the early stages of exercise, and there was a temporary interruption in the increase of Msw. This interruption in sweating was affected by the rate of change in Tsl rather than by the absolute value of Tsl, since there was a positive and significant correlation between the time of the interruption in the increase of Msw and the rate of decrease in Tsl (y = 6.47 x +0.04; r = 0.86, P < 0.05). The results suggest that sweating response in the early stages of exercise may be influenced by changes in local skin temperature due to evaporative cooling.