Nonthermal factors for control of heat loss during exercise are suggested to be one of the mechanisms that improve the heat loss response in humans with physical training. The purpose of this study was to investigate the relationship between the magnitude of the nonthermal factors and the heat loss response. Eight healthy male subjects participated in this study. They performed an isometric handgrip (IH) exercise for 60 sec at four different intensities (15, 30, 45, and 60% of maximal voluntary contraction - MVC) at an ambient temperature of 35℃ and a relative humidity of 50%. Esophageal temperature and mean skin temperature did not change with the rise in exercise intensity and were similar at all exercise intensities, while the heart rate (HR), rating of perceived effort (RPE), and mean arterial pressure (MAP) all increased with intensity. The sweating rate (SR) on the chest, and the right and left forearm and palm increased with the rise in intensity, although the pattern of the change in SR on the palm differed from that on the other body sites. The SR on the chest and forearm were significantly above the pre-exercise level when the exercise intensity was 30% MVC or more, while the change in SR on the palm was significantly increased at 45% MVC or more. The skin blood flow (SkBF) and cutaneous vascular conductance (CVC) on the chest and left forearm increased with exercise intensity, although the differences in CVC with exercise intensity were not marked. Furthermore, the SkBF and CVC at both these sites did not change significantly from the level at 15% MVC. The results indicate that nonthermal factors cause the changes in the heat loss response with a rise in IH exercise. These responses were induced at intensities of 30%MVC or more, although the heat loss response was greater with a rise in the magnitude of the nonthermal factors.

DESCENTE SPORTS SCIENCE Vol.21/THE DESCENTE AND ISHIMOTO MEMORIAL FOUNDATION FOR THE PROMOTION SPORTS SCIENCE