To prevent heat stroke, we aimed to clarify the relationship between core body temperature and physiological measurements during incremental load test under hot environment. Subjects exercised under hot environment (33°C for air temperature, 60％ for humidity) with measuring rectal temperature and other physiological measurements. In results, the increase of heart rate correlated with not only increase of rectal temperature at the same point in time but also the value after 5 or 10 minutes. Our results suggested that heart rate was useful physiological value as related or estimated core temperature.
