The Effect of Menstrual Cycle and Oral Contraceptive Pill Phase on Aspects of Exercise Physiology

This study will investigate the effect of menstrual cycle (MC) and oral contraceptive pill phase on aspects of exercise physiology and athletic performance in female athletes. Specifically, this study intends to investigate the effects of circulating fluctuations in oestradiol and progesterone, experienced during the menstrual cycle and oral contraceptive pill use, on aspects of exercise physiology and athletic performance in female athletes. This research will help researchers determine if a particular hormonal profile affects physiological functioning such as muscle strength, maximum oxygen uptake and athletic performance in female athletes.

Inclusion Criteria:Cis gender women18-40 years of ageBody mass index ≥ 19.5 and ≤ 25 kg∙-2; an exception can be made in the case of some athletes where they have a higher BMI, but are considered more lean/muscular than fat.Must be defined as healthy, i.e., not having any medical condition or taking any medication known to affect any of the outcome measures. Examples include diagnosed hyperandrogenism from polycystic ovary syndrome, congenital adrenal hyperplasia, or other differences in sexual development.Cannot smokeConsidered to be physically active. Participants training status will be classified using the criteria outlined by McKay et al. (In press). For this study, participants must be Tier 2 athletes or above (Table 1). In addition, participants will be considered on the basis of relative maximal oxygen consumption (Decroix et al., 2016); needing to be Performance Level 2 or above (Table 2). Participants must provide details on gravidity and parity and must not be in the postpartum period (i.e., within 12 months of childbirth), currently breastfeeding, or pregnant. Participants will be recruited based on their endogenous hormonal profile (i.e., eumenorrheic or OCP users) and these profiles (including inclusion/exclusion criteria) are described below in detail.Group Specific Inclusion Criteria:Group 1. Eumenorrheic [EUM]Must have menstrual cycle lengths ≥ 21 days and ≤ 35 days resulting in 9 or more consecutive periods per yearMust provide evidence of a luteinising hormone (LH) surgeMust demonstrate the required hormonal profile as defined in Table 3Cannot have used any type of hormonal contraceptives (HC) for a minimum of 3 months, but ideally 6 months, prior to enrolmentGroup 2. Oral contraceptive pill [OCP] usersMust have been taking their OCP ≥ 3 months prior to recruitmentMust be taking a combined, monophasic, second generation OCP (see Table 4 for permitted brands)Must demonstrate the correct hormonal profile as defined in Table 5Exclusion Criteria:-Cannot speak, read and understand English