Influence of Menstrual Cycle Phase on Adaptations to Sprint Interval Training

Inclusion Criteria: * Participating in 150 min of moderate-vigorous physical activity/week * VO2peak of 'good' or above based on American College of Sport Medicine (ACSM) normative values(greater than 35.0ml/kg/min) * Body mass index (BMI) between 18-27 kg/m2 * Performing 2-4 structured exercise sessions/week. * Weight stable (within ± 2kg for at least 6 months) * Non-smoker * Menstrual cycle length of 27-35 days * Minimal menstrual cycle length variability (less than 3 days) * Ovulating monthly evidenced by a positive urinary luteinizing hormone surge * Blood progesterone concentration greater than 16 nmol/L. Exclusion Criteria: * Hormonal contraceptive use within the last 3 months * Polycystic ovarian syndrome (PCOS) or endometriosis * Failure to meet MC verification criteria. * Diagnosed with cardiovascular or metabolic disease, hyper- or hypogonadism, and/or PCOS * The use of medication for managing blood glucose or lipid metabolism * Current use of oral contraceptives or use within the last 3 months * Irregular menstrual cycles (\<27 days or \>35 days) * Pregnant or post-partum in the last 12 months, lactating or breast feeding within 3 months of the start of study, or menopausal * Recreational smoking tobacco * Inability to perform the study exercise protocols or follow the pre-trial dietary or physical activity controls * Taking medications affecting substrate metabolism (corticosteroids or nSAIDs) * Actively engaging in a low-carbohydrate diet (e.g., ketogenic, Atkins)