Abstract
INTRODUCTION: To evaluate the effects of oral contraceptive (OC) and hormonal intrauterine device (H-IUD) use, compared with an eumenorrheic (EUM) cycle, on maximal strength and power between hormone phases. METHODS: One-repetition maximum (1RM) leg press and bench press, peak force from knee extension and upright row isometric dynamometry, and power from vertical jump height and reactive strength index (cm·s -1 ) were measured in 60 healthy, active women (mean ± SD; age: 26.5 ± 7.0 yr, body mass index: 23.8 ± 3.0 kg·m -2 ) who were monophasic OC users for ≥6 months ( n = 21), had an H-IUD for ≥6 months ( n = 20), or had regularly naturally occurring menstrual cycle for ≥3 months or were using a nonhormonal IUD (EUM; n = 19). Participants were randomly assigned to begin in the follicular phase/placebo pill (low hormone phase (LHP)) or in the luteal phase/active pill (high hormone phase (HHP)) and were tested once in each phase. Estimates of total lean mass (LM), leg LM, and arm LM were measured via dual energy x-ray absorptiometry. Separate univariate ANCOVAs were used to assess the change from HHP to LHP between groups, with LM and progesterone as covariates. RESULTS: Leg press 1RM was significantly different across phases between groups ( P = 0.037), with higher leg press 1RM in the HHP for the OC group (mean difference [∆ HHP - LHP] ± standard error: ∆ 7.4 ± 15.9 kg; P = 0.043) compared with the H-IUD group (∆ -8.9 ± 23.8 kg; P = 0.043). All groups demonstrated similar bench press 1RM, peak force, vertical jump height, and reactive strength index between phases ( P > 0.05). CONCLUSIONS: Lower body strength was greater in the HHP for OC users (5.6% increase) suggesting that lower body maximal strength outcomes may be influenced by hormonal contraception type.