Six male subjects were exposed to combined stress of heat and exercise, and their heart rate, blood pressure, oxygen uptake, skin temperature, esophageal temperature and body weight were measured. These observations were repeated 12 times for each subject under 4 levels of WBGT (Wet Bulb Globe Temperature) : 22, 26, 30, 32.5°C at rest and at 2 levels of exercise intensity : 150 W/m² (Ex. 150W) and 250 W/m² (Ex. 250 W) . The results obtained were as follows:
1. Significant differences were found in heart rate, oxygen pulse and rate pressure product at 32.5t WBGT and Ex. 150 W and at 30 and 32.5t WBGT and Ex. 250W compared with those at 22t WBGT.
2. Significant increases in esophageal temperature were observed at 32.5°C WBGT and Ex. 150 W and at 30 and 32.5t WBGT and Ex. 250 W.
3. The body weight loss at 26, 30 and 32.5 C WBGT was significantly higher than that at 22°C WBGT for both Ex. 150 W and 250 W.
4. These results suggest that there is a risk of heat exhaustion at WBGT higher than 30-32.5°C under mild exercise and above 26-30°C WBGT at a moderate exercise level. The upper limit for moderate exercise (Ex. 250W) is suggested to be 30°C WBGT.