Sex hormones and environmental factors affecting exercise

Abstract

Reproductive hormones and environmental conditions can influence physiological systems such as fluid regulation and thermoregulation, which in turn can impact exercise. There are numerous challenges with performing physiological studies on women due to the changing hormonal profiles that occur across the menstrual cycle, in addition to the various types of exogenous hormonal contraceptives used by women. Over the last 20 years, our laboratory has performed a number of research studies to examine sex and sex hormone effects on fluid regulation and temperature regulation in humans. In addition, our laboratory has developed a novel way to control reproductive hormone exposure in young women and to isolate the effects of individual sex hormones on physiological systems. Research findings in our laboratory and others show that there are sex differences and menstrual cycle differences in the osmotic release of arginine vasopressin (AVP) and onset of thirst during hyperosmotic conditions such as dehydration, and that these differences are primarily driven by estradiol. With respect to temperature regulation, progesterone increases core temperature and delays the threshold for the onset of sweating, whereas estradiol reduces the onset of sweating threshold, resulting in higher sweat rates for a given core temperature, favoring heat dissipation. However, exercise training may attenuate these sex hormone effects on sweating. Lastly, as alterations in sex hormones occur in conditions such as polycystic ovary syndrome or with aging and menopause, fluid balance and temperature regulation may become impaired. Additional research is needed to characterize the physiological effects of sex hormone exposure (beyond estradiol), particularly in special populations, at rest and during exercise given the numerous health benefits of physical activity.