Submitted on August 11, 2004
Accepted on January 24, 2005
Effects of menstrual cycle and physical training on heat loss responses during dynamic exercise at moderate intensity in a temperate environment
Tomoko Kuwahara1, Yoshimitsu Inoue2, Miyako Abe2, Yuki Sato2, and Narihiko Kondo1*
1 Laboratory for Applied Human Physiology, Faculty of Human Development, Kobe University, Kobe, Japan
2 Laboratory for Human Performance Research, Osaka International University, Osaka, Japan
* To whom correspondence should be addressed. E-mail: kondo{at}kobe-u.ac.jp.
We evaluated the effects of the menstrual cycle and physical training on heat loss (sweating and cutaneous vasodilation) responses during moderate exercise in a temperate environment. Ten untrained (group U) and seven endurance-trained (group T) women (maximal O2 uptake: VO2max, 36.7 ± 1.1 vs. 49.4 ± 1.7 ml/kg/min, respectively; p < 0.05) performed a cycling exercise at 50% VO2max for 30 min during both the mid-follicular and mid-luteal menstrual phase in a temperate environment (ambient temperature, 25°C; relative humidity, 45%). In group U, plasma levels of estrone, estradiol, and progesterone at rest and esophageal temperature (Tes) during exercise were significantly higher during the mid-luteal than the mid-follicular phase (p < 0.05). The sweating rate (SR) and cutaneous blood flow (% LDF) on the chest, back, forearm, and thigh were lower in the mid-luteal than in the mid-follicular phase during exercise. The Tes threshold for heat loss responses was significantly higher and the sensitivity of the heat loss responses was significantly lower in the mid-luteal than in the mid-follicular phase, regardless of body site. These effects of the menstrual cycle in group U were not observed in group T. The SR and % LDF were significantly higher in group T than in group U, regardless of menstrual phase or body site. The Tes threshold for heat loss responses was significantly lower and the sensitivity of heat loss responses was significantly greater in group T than in group U in the mid-luteal phase; only the sensitivity of the sweating response was significantly greater in the mid-follicular phase. These results suggest that heat loss responses in group U were inhibited in the mid-luteal phase, as compared to the mid-follicular phase. There were no remarkable effects of the menstrual cycle in group T. Physical training improved heat loss responses; this improvement was more marked in the mid-luteal than the mid-follicular phase.
