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 [Delta HHP - LHP] ± standard error: Delta 7.4 ± 15.9 kg; P = 0.043) compared with the H-IUD group (Delta -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.
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