Comparison of sweating components during endurance exercise under the same load in a hot environment and in a neutral thermal environment

Sweat contains electrolytes (minerals), therefore, it is necessary to consider its loss through sweat in the fluid replacement strategy in sports. The purpose of this study was to compare the concentration of components in sweat, such as electrolytes (minerals), when endurance exercise is performed in hot and neutral thermal environments. Eight men cycled for 60 min at 55% VO2peak under two envitonment conditions: a hot environment (WetBulb Globe Temperature (WBGT): 29.0±0.2℃; Heat) and a neutral thermal environment (WBGT: 20.5±0.2℃; Con). During exercise, sweat loss, core temperature, and heart rate (HR) were measured, and sweat from the chest, back, and thigh was collected. The core temperature, sweat loss, and HR increased significantly in Heat. The sweat electrolyte concentration was significantly higher in Heat than in Con only for Na. Regarding the amount of electrolyte loss from sweat, Na and K showed a significantly higher value than Con in Heat in comparison of each region, and the total loss amount of three regions in Cu also had a significantly higher value than Con in Heat. In addition, there was no difference in the concentration of Ca and Cu between the regions, but there was a significant difference in the amount of loss. It was concluded that even if there was no difference in the electrolyte concentration in sweat, the amount of electrolyte loss increased in K and Cu in a hot environment, and that there was a site difference in the amount of loss in Ca and Cu.