Evaluation of Hormonal Contraception Effects on Strength and Recovery Across the Hormone Cycle

Few investigations have evaluated the effects of hormonal contraception on exercise performance. The biphasic response of endogenous hormones in eumenorrheic (EUM) females is altered with the delivery of exogenous hormones, with oral contraceptives (OC) and intrauterine devices (IUD) most commonly used. Hormonal alterations may have undesirable consequences on muscle strength and power performance, fatigability, and recovery. The purpose of the study was to evaluate the effects of OC and IUD use, compared to a EUM cycle, on maximal strength, power, fatigability, and recovery between menstrual cycle (MC) phases. Sixty healthy, active women who were monophasic OC users (n=21), had a hormonal-IUD (H-IUD; n=20), or had regular naturally occurring menstrual cycles or were using a non-hormonal IUD (EUM; n=19) were evaluated in the in the follicular phase/placebo pill (FP) or in the luteal phase/active pill (LP). Strength was assessed from upper and lower body one repetition max (1RM) and peak force from isometric dynamometry. Power was assessed from counter movement jump and reactive strength index. Peak power (PP), average power (AP), time to PP, and fatigue index were measured with a repeated sprint ability test (RSA). Blood lactate, vessel diameter, and blood flow were measured prior to and immediately post-RSA. Leg press 1RM was significantly different across the MC between groups (p=0.027), with higher leg press 1RM in the LP for the OC group (mean difference[MD: ∆LP-FP]±standard error [SE]: ∆7.3±4.5 kg; p=0.045) compared to the IUD group (∆-8.8±4.6 kg; p=0.045). The results showed no significant changes across the MC for other study outcomes (p>0.05). Despite no significance, the H-IUD group (Δ320.3±260.3 W) and EUM group (Δ24.0±13.3 W) demonstrated greater changes in AP and PP, respectively, in the LP while the OC exhibited greater AP in the FP (Δ-248.2±254.0 W). All groups demonstrated greater blood flow in the FP (OC:Δ-133.4±10.3 mL/min; H-IUD:Δ-128.6±10.6 mL/min; EUM:Δ-137.3±10.8 mL/min) after exercise. Collectively, OC and H-IUD users have similar performance and recovery across the MC, suggesting that exercise training does not need to be modified for phase or group. It appears that OC and H-IUD users can be equally included in research with EUM women.Doctor of Philosoph