抄録
The purpose of this study was to determine the effects of initial hydration status and core temperature on endurance capacity in untrained individuals during heavy exercise in a hot environment. In addition, we also examined the final core temperature at exhaustion in untrained individuals. Untrained subjects (n=6) performed three cycle exercise trials at 80% VO2max until exhaustion in a climatic chamber (32°C, 60% RH) under the following three conditions: 1) 2% hypohydration + 38.2°C rectal temperature; H2, 2) 1% hypohydration + 37.8°C rectal temperature; H1, 3) euhydration + 37.6°C rectal temperature; EU. Before each exercise trial, subjects performed 100 min of exercise in which their hydration status and core temperature were altered. Exercise tolerance time averaged 7.7±1.5, 14.0±2.4, and 20.9±3.7 min during H2, H1, and EU, respectively; a significant difference was found only between H2 and EU. Subjects reached exhaustion at a consistent final rectal temperature of 38.4±0.1°C regardless of those trials. Exercise tolerance time was strongly related to the initial levels of rectal and mean body temperatures and the increases in rectal, mean skin, and mean body temperatures during exercise. It is concluded that hypohydration-induced higher initial core temperature have a detrimental effect on endurance capacity in untrained individuals during heavy exercise in a hot environment. [J Physiol Sci. 2007;57 Suppl:S189]
