Maximal oxygen uptake, sweating and tolerance to exercise in the heat.

Abstract

The purpose of this experiment was to determine if tolerance to exercise in the heat is related to maximal oxygen uptake (max $${\dot V}$$ 02) and sweating. Seven men with max $${\dot V}$$ 02 between 42 and 66 ml/(min·kg) underwent one 2-hr exposure at 24°C Tq while working on a bicycle ergometer at $$\overline {\text{X}}$$ rel $${\dot V}$$ 02 of 28% ( $$\overline {\text{X}}$$ $${\dot V}$$ 02 = 1.23 1/min). In the hot exposures the high capacity subjects had maximal sweat rates of 800 to 1,000 g/(hr·m2) while the lower capacity men sweated 300 to 400 g/(hr·m2). These differences in sweating were not related to neuromuscular stimuli, $${\dot V}$$ 02 (metabolic rate), Tre, ΔTre, $$\overline {\text{T}}$$ s, Δ $$\overline {\text{T}}$$ s or tolerance time. Tolerance to exercise in the heat was not related to maximal $${\dot V}$$ 02 capacity when the subjects worked at the same relative load in spite of large differences in sweating. These results question the importance of the rate of sweating for predicting work performance in hot environments.