The sweating responses of athletes trained on land and in water

In order to examine whether different sweating responses of athletes trained on land and in water may be ascribed to changes in the central sudomotor mechanisms and/or those of the peripheral mechanisms of sweat glands, we measured the local sweating rate at the left forearm (mswf) and the left scapula (msws), the frequence of sweat expulsion (Fsw) and body temperatures (mean skin temperature and rectal temperature: Tre) in six runners and five soccer players (R group) and six swimmers (S group) during progressive thermal stress at rest (2 degrees C increase in ambient temperature every 15 min from 35 to 45 degrees C RH = 30-40%). Tre and heart rate at the end of experiment did not differ significantly between the groups (37.31 +/- 0.04 degrees C, 74.5 +/- 7.9 beats.min-1 in the S group and 37.27 +/- 0.07 degrees C, 71.1 +/- 9.0 beats.min-1 in the R group, respectively). The msws and mswf at any given mean body temperature (Tb) were greater in the S group than in the R group. Although the regression line showing the relationship between Fsw and Tb in the S group was shifted to the left of that in the R group, there was no significant difference in the slope of the lines. The msws-Fsw or mswf-Fsw regression line was not different between the two groups. These results indicate that the higher sweating rate in the S group may be ascribed to a difference in the centrally derived sudomotor neural activity, but not to that in the peripheral mechanisms of sweat gland activity.