The effects of exercise intensity on thermoregulatory responses to exercise in women

We investigated the influence of altering exercise intensity (150, 300, and 450 kpm/min) on the resetting of the core temperature threshold for the onset of the sweating rate (M(sw)) and the alteration of sweating sensitivity during the menstrual cycle in women. Five women underwent cycling exercise for 30 min in both the luteal and follicular phases under controlled neutral environmental conditions (T: 25 degrees C, RH: 55%). A significantly higher rectal temperature (T(re)) was seen in the luteal phase at all exercise intensities, and the same time course of the T(re) response with a constant difference of approximately 0.2 degrees C was shown between the follicular phase and the luteal phase. The T(re) threshold for M(sw) was also apparently shifted rightward a constant value of 0.2 degrees C from the follicular phase to the luteal phase, independent of the alteration of exercise intensity. The slope of the M(sw)-T(re) relationship in the follicular phase did not differ from that in the luteal phase. These results indicate that (1) a rightward shift in the T(re) threshold from the follicular phase to the luteal phase can be observed independent of any alteration of the exercise intensity; and (2) the sensitivity of M(sw) is also not physiologically influenced by exercise intensity. Thus, alterative thermoregulation during the menstrual cycle was fundamentally unaffected by the change of exercise intensity.