The effect of oral contraceptive cycle phase on female athletic performance

[Truncated abstract] Despite the widespread use of oral contraceptives by the female athletic population, limited information exists regarding the influence of oral contraceptive (OC) usage on the exercise responses of women. Anecdotally, female athletes have manipulated their menstrual cycle with hormonal agents in the belief that they can optimise performance by aligning competition with a specific cycle phase. Therefore, the studies comprising this thesis aim to provide female athletes, coaches and sport scientists with practical knowledge regarding how physiological and performance measures may be affected by the variation in hormones associated with a monophasic OC cycle. Each study involved the assessment of a variety of physiological and performance parameters at three phases of a monophasic OC cycle; during the OC consumption phase (CONS), early in the OC withdrawal phase (WITH1) and late in the OC withdrawal phase (WITH2). The aim of the first study (Chapter 3) was to investigate whether aerobic endurance was affected by the acute hormonal changes of an OC cycle. A 1 h cycling protocol was used as the assessment tool, based on the established reliability of the test. At the three time points of the OC cycle, 13 female cyclists/triathletes (mean peak VO2 = 53.0 + 5.6 mlkg–1min–1) underwent measures of power output, heart rate, ventilation (VE), oxygen consumption (VO2), respiratory exchange ratio (RER), rating of perceived exertion (RPE), blood lactate, blood glucose and resting endogenous serum oestradiol and progesterone.