Metabolic and thermoregulatory responses to exercise during the human menstrual cycle

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Abstract
Six healthy adult females with presumptively normal menstrual cycles volunteered to exercise on a bicycle ergometer on 5 separate days (days 2, 8, 14, 20 and 26 of the menstrual cycle; day 1 = onset of menstruation). On each experimental day each subject exercised at 4 submaximal exercise intensities and at an exercise intensity that elicited a peak O2 uptake. At rest and at each exercise intensity, metabolic and thermoregulatory measurements were made. There were no changes at rest or at any exercise intensity relative to cycle day in absolute O2 uptake (1 .cntdot. min-1). Mean peak O2 uptake and average work time to exhaustion were not different during the various phases of the menstrual cycle. The mean core temperature (Tre) at each exercise intensity was elevated on days 14 and 20 above that observed during flow (day 2)and the follicular phase (day 8). This implied a dissociation of metabolic responses from thermoregulatory responses to exercise during the human menstrual cycle similar to that previously observed in exercising febrile males.