THERMOREGULATION AND THE MENSTRUAL-CYCLE

  • 1 January 1982
    • journal article
    • research article
    • Vol. 53  (8) , 790-794
Abstract
Four women, aged 20-35 yr, exercised at .apprx. 30% .ovrhdot.VO2 max in 3 environments (28.degree. C, 12.6 torr vp [1/760 atm venous pressure]; 35.degree. C, 28.0 torr vp; 48.degree. C, 8.7 torr vp) during 3 stages of the menstrual cycle: ovulation, luteal phase and flow. Cycle phase was confirmed by hormone analysis for estradiol-17.beta. and progesterone in venous blood samples. Although pre-exposure core temperature and O2 uptake were higher in the luteal phase, these differences disappeared under the combined influence of exercise and heat stress. Exercise heart rate, core temperature and sweat rate were similar in all cycle phases. O2 uptake, ventilatory volume, cardiac output, stroke volume, blood electrolytes, blood pressure, body weight and tolerance time were unaffected by cycle phase. In the 28.degree. C environment, mean skin temperature and forearm bloodflow were lower in the luteal phase than during flow, but this difference was not observed in 35.degree. C or 48.degree. C. A greater relative decrease in plasma volume was observed in the luteal phase following exercise in 48.degree. C than during flow. The overall response of women to exercise and heat stress during 3 phases of the menstrual cycle suggest that minor cyclic alterations in physiological systems apparent at rest are masked by the demands of the activity and the environment.

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