The Effects of Exogenous Estrogen and Menstrual Cycle Phase on Female Aerobic Performance

Abstract

This thesis investigates aerobic performance and substrate utilization of eumenorrheic women on and off oral contraceptive pills (OCP) during the follicular and luteal phases of the menstrual cycle. The topic was chosen as the relevance of oral contraceptives to today’s athletic industry is increasing with the progression of womens athletics. The implementation of OCPs by women of the general population continues to gain momentum for the benefits of reduced cycle variability and symptoms of the menstrual cycle. Many studies have demonstrated a decrease in VO2max that occurred in women taking OCPs, suggesting that exogenous estrogen negatively impacts aerobic capacity, with potential implications for elite performance. Elevated endogenous estrogen concentrations – such as in the follicular phase – provide a cardioprotective effect, positively influencing VO2max. While progesterone’s antiestrogenic properties are well known, the two primary female sex hormones find common ground with regard to increased lipid mobilization in the luteal phase. However, while fluctuations of endogenous sex hormones have some effect on triglyceride mobilization, synthetic hormones found in OCPs further increase triglyceride mobilization and plasma cortisol concentrations in exercising women. This thesis provides a review of the effects of OCPs on aerobic performance and appreciates cycle phase differences, providing a foundation for broader assessments of effects of OCPs in women of the general population. Additional research on this topic would allow for a greater understanding of the influence of sex hormones on cardiovascular mechanisms to a further extent.