Influence of Ovarian Hormones on the Skeletal Muscle Response to Resistance Exercise

Abstract

Divergent sex hormones underpin a primary biological difference between male and female adults. While the anabolic effects of androgens are well-documented, the influence of ovarian hormones on skeletal muscle is poorly understood. The overarching objective of this dissertation was to explore the influence of endogenous and exogenous ovarian hormones on the muscle protein synthetic response to resistance exercise training. The purpose of study 1 was to examine the interindividual variability in hormone levels and ovulation timing across the menstrual cycle in a combined sample of naturally menstruating individuals. The aim of study 2 was to assess muscle protein synthesis during the late follicular phase (i.e. highest estradiol concentration) compared to the mid-luteal phase (i.e. highest progesterone concentration) in naturally menstruating individuals. In study 3, we utilized the methodological design from study 2 to compare the response during the active pill phase to the inactive/placebo pill phase in habitual oral contraceptive pill users. We conclude that short-term fluctuations in endogenous or synthetic ovarian hormones do not affect exercise-induced increases in muscle protein synthesis or whole-body myofibrillar protein breakdown in response to resistance exercise. These studies contribute to our understanding of the influence of endogenous and exogenous hormone fluctuations on the response to resistance exercise, highlight the variability in cycle length, ovulation timing, and hormone levels, and provide a valuable resource for future research in female participants. In the absence of high-quality data showing a significant influence of menstrual cycle or oral contraceptive pill phase on exercise-induced adaptations or performance, premenopausal female participants should not be excluded from exercise science studies solely for concerns about hormonal status as a confounding variable.