Oral Contraceptives Do Not Affect Physiological Responses to Strength Exercise

ABSTRACT: Umlauff, L, Weil, P, Zimmer, P, Hackney, AC, Bloch, W, and Schumann, M. Oral contraceptives do not affect physiological responses to strength exercise. J Strength Cond Res 35(4): 894-901, 2021-This study investigated the effect of oral contraceptive (OC) use on acute changes in steroid hormone concentrations and tryptophan (TRP) metabolites in response to strength exercise. Twenty-one women (age: 23 ± 3 years), 8 combined OC users (OC group) and 13 naturally cycling women (menstrual cycle [MC] group), participated. Testing was performed during the pill-free interval for the OC group and the follicular phase for the MC group. Subjects completed an intense strength exercise protocol (4 × 10 repetitions back squat). Blood samples were taken at baseline (T0), post-exercise (T1), and after 24 hours (T2) to determine serum concentrations of cortisol, estradiol, testosterone, TRP, and kynurenine (KYN). Statistical significance was defined as p ≤ 0.05. At T0, the OC group showed higher cortisol (OC: 493.7 ± 47.1 ng·mL-1, MC: 299.1 ± 62.7 ng·mL-1, p < 0.001) and blood lactate (OC: 1.81 ± 0.61 mmol·L-1, MC: 1.06 ± 0.30 mmol·L-1, p = 0.001) and lower estradiol (OC: 31.12 ± 4.24 pg·mL-1, MC: 38.34 ± 7.50 pg·mL-1, p = 0.023) and KYN (OC: 1.15 ± 0.23 µmol·L-1, MC: 1.75 ± 0.50 µmol·L-1, p = 0.005). No significant interactions (group × time, p > 0.05) were found for the hormones and TRP metabolites assessed. Oral contraceptive use did not affect the physiological response of steroid hormones and TRP metabolites to acute strength exercise during the low hormone phase of the contraceptive or MC in healthy young women, even when some baseline concentrations differed between groups. Consequently, these findings provide important implications for practitioners testing heterogeneous groups of female athletes.