Intersexual comparison of thermal, cardiac and muscular responses at the time of a prolonged course in a hot environment

The aim of this study was to compare male and female thermal, cardiac, and muscular responses induced by a prolonged run undertaken in a hot environment. Twelve volunteers participated in this study. The first group consisted of 6 men and the second one consisted of 6 women. After determination of their VO(2)max and maximal aerobic velocity (MAV), each athlete completed a 40-min run at 65% MAV in a hot and dry environment (temperature 31-33 degrees C, relative humidity 30%). Immediately before and after the run, each subject performed two different vertical jumps, i.e., a squat jump (SJ) and a counter-movement jump (CMJ) on a force platform. Force, velocity, power and jump height were measured during each jump. The completion of the run was associated with a significant loss (p < 0.001) of body mass (BM) and significant increases (p < 0.001) in heart rate, tympanic temperature, and lactate concentration ([La]). Muscle power was significantly improved (+9%, p < 0.05) during the SJ only in the women. A significant enhancement of this parameter was also demonstrated during the CMJ in both groups (men: +10%, p < 0.05; women: +8%, p < 0.01). Surprisingly, a comparison of thermal, cardiac, and muscular responses did not reveal any significant differences between the sexes. Moderate dehydration (-2.0 to -2.3% of BM) and a rise in core temperature (above 39.2 degrees C) induced by the 40-min run led to an improvement of muscular strength in both men and women. However, the results of this study did not reveal any significant between-sex differences in thermal, cardiac, and muscular responses after exercising in the heat.