Temperature and sweating responses in one-legged and two-legged exercise

Summary

In looking at the thermoregulatory responses resulting from symmetrical or asymmetrical exercise, this paper has focused on the effect of local skin temperature (T _{sk, local}) on local sweat rates (m _sw,local) during one-legged (W ₁) and two-legged (W ₂) exercise on an ergocycle. Five subjects underwent four 3-h tests at 36° C, each consisting of six 25-min exercise periods alternating with 5-min rest periods. The subjects performed W ₁ and W ₂ at 45 and 90 W, respectively, either dehydrated or rehydrated. Body temperatures and total sweat rate were measured as well as four m _sw,local (on chest and thighs), assessed from sweat capsules under which T _{sk, local} was maintained at predetermined levels (37.0°C and 35.5°C). The combinations of T _{sk, local} levels, capsule locations, exercise intensity and hydration level chosen in our protocol led to the following results. The hydration level affected rectal temperature but not total or m _sw,local. No specific effect of muscle activity was found; m_sw,local on thighs of resting and working legs were similar. The m_sw,local were only influenced by exercise intensity, m_{sw, local} being more elevated during the higher intensity. No significant effect of T _sk,local on m_sw,local was found, whatever the experimental condition and/or the location. It was concluded that local thermal effects on m_sw,local could have been masked by the strong central drive for sweating which has been found to exist in subjects exercising in a warm environment.