Sweating responses during heat acclimation and moderate conditioning

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Abstract
Five young men underwent 8 days of heat acclimation (bicycle ergometer; 50% .ovrhdot.VO2 max [maximum O2 consumption]; 2 h/day) at 39.8.degree. C db, 30.0.degree. C wb. A control group underwent the same exercise procedure at 24.degree. C. Local sweat rates (SR) for chest, thigh and arm were highest on the arm and lowest on the thigh throughout acclimation. Acclimation resulted in SR increases on all 3 sites, thigh SR showing the largest percentage increase. Rectal temperature (Tre) at the onset of sweating decreased 0.49.degree. C from day 1-day 8. Chest and thigh SR showed higher relationships with mean body temperature (Tb) than total body SR and Tre at the onset of sweating. In the control group, SR decreased on all 3 sites. Thigh SR, which was the lowest on day 1, showed the smallest decrease so that by day 7 SR did not differ between the three sites. Tre at the onset of sweating decreased 0.19.degree. C during conditioning and it correlated (r = 0.72) with Tb. Similar relationships were found for chest and total body SR. Acclimation and conditioning result in relatively more SR on the limbs than on the torso, but these changes are less related to Tb than torso SR. Sweating sensitivity increases during both procedures, but its contribution to heat acclimation is minor.