Effects of exercise intensity on the sweating response to a sustained static exercise

Abstract

To investigate how the sweating response to a sustained handgrip exercise depends on changes in the exercise intensity, the sweating response to exercise was measured in eight healthy male subjects. Each subject lay in the supine position in a climatic chamber (35°C and 50% relative humidity) for ∼60 min. This exposure caused sudomotor activation by increasing skin temperature without a marked change in internal temperature. After this period, each subject performed isometric handgrip exercise [15, 30, 45, and 60% maximal voluntary contraction (MVC)] for 60 s. Although esophageal and mean skin temperatures did not change with a rise in exercise intensity and were similar at all exercise intensities, the sweating rate (SR) on the forearm increased significantly ( P < 0.05) from baseline (0.094 ± 0.021 mg ⋅ cm−2 ⋅ min−1at 30% MVC, 0.102 ± 0.022 mg ⋅ cm−2 ⋅ min−1at 45% MVC, 0.059 ± 0.009 mg ⋅ cm−2 ⋅ min−1at 60% MVC) in parallel with exercise intensity above exercise intensity at 30% MVC (0.121 ± 0.023 mg ⋅ cm−2 ⋅ min−1at 30% MVC, 0.242 ± 0.051 mg ⋅ cm−2 ⋅ min−1at 45% MVC, 0.290 ± 0.056 mg ⋅ cm−2 ⋅ min−1at 60% MVC). Above 45% MVC, SR on the palm increased significantly from baseline ( P < 0.05). Although SR on the forearm and palm tended to increase with a rise in exercise intensity, there was a difference in the time courses of SR between sites. SR on the palm showed a plateau after abrupt increase, whereas SR on the forearm increased progressively during exercise. These results suggest that the increase in SR with the increase in sustained handgrip exercise intensity is due to nonthermal factors and that the magnitude of these factors during the exercise may be responsible for the magnitude of SR.