Abstract des Autors

We investigated whether menstrual cycle phase would affect temperature regulation during an endurance exercise bout performed at room temperature (Ta) of 22 deg C and 60% relative humidity. Nine eumenorrheic women (27.2 +/- 3.7 yr, peak VO2 2.52 +/- 0.35 l/min) performed 60 min of cycle exercise at 65% of peak VO2. Subjects were tested in both midfollicular (F) and midluteal (L) phases, although one women did not show a rise in serum progesterone (P4) that is typically evident 1 wk after ovulation. VO2, rectal (Tre) and skin (Tsk) temperatures, heart rates (HR), and ratings of perceived exertion (RPE) were measured throughout exercise. Sweat loss (SL) was estimated from pre- and postexercise body weight differences. VO2, SL, and Tsk were not affected by menstrual cycle phase. Preexercise Tre was 0.3 deg C higher during L than during F conditions, and this difference increased to 0.6 deg C by the end of exercise. Compared with F, HRs during L were ca. 10 beats/min greater at all times, whereas RPE responses were significantly greater by 50 min of cycling. No differences in any measured values were found in the subject whose P4 was low in both test conditions. Results indicate that thermoregulation (specifically, regulation of Tre), as well as cardiovascular strain and perception of exercise, was adversely affected during the L phase. Verf.-Referat