Thermal stress is known to impair endurance performance. However, the capacity to continue intermittent high-intensity exercise is required in many ball sports. There is relatively little available knowledge concerning the effects of heat stress and thermal dehydration on the capacity to continue intermittent high-intensity exercise. The aim of the present study was to clarify the influence of heat stress and thermal dehydration on the capacity to continue intermittent high-intensity exercise in elite ball game players. Three volleyball (V league) and one soccer (J league) player repeatedly performed human power output maximal knee extension at intervals of 15 seconds during two 20 min session (E-1, E-2) with 10 min of rest in between, on a anaeropress machine. The exercise was performed in the following environments, the control environment [25.0°, 40% relative humidity (RH)], a heat environment [30.0°, 40% RH] and a thermal dehydration (about 3% weight loss) [25.0°, 40% RH]. Peak power, electromyogram (EMG) of vastus medialis, heart rate (HR), oxygen uptake (VO2), body temperature (BT) were measured during exercise in each environment. Peak power output decreased in the thermal dehydration environment rather than in the heat environment in three volleyball players. However, peak power output did not decrease in the soccer player in either environmental condition. HR of all players showed the highest value in the thermal dehydration environment. These results indicated that the thermal dehydration of about 3% weight loss seemed to be more significant for ball game players than the heat stress of 30° during the Japanese summer.
© Copyright 1999 5th IOC World Congress on Sport Sciences with the Annual Conference of Science and Medicine in Sport 1999. All rights reserved.