Menstrual Cycle Phase Does Not Influence Training-Induced Muscle Hypertrophy or Strength: A Randomized Controlled Trial

Resistance exercise training (RET) promotes muscle hypertrophy and strength. In females, menstrual cycle (MC)-based fluctuations in estradiol and progesterone have been postulated to influence RET-induced adaptations. It remains unclear whether periodizing RET across the MC (MC phase-based training; MCPBT) provides advantages when rigorous hormonal confirmation and balanced training loads are applied. Aim: We investigated the influence of MCPBT on muscle hypertrophy and strength in response to RET over three MCs. Methods: Employing a randomized, unilateral design, twenty-four healthy, eumenorrheic females completed a within-participant resistance training trial across three consecutive MCs (12.2 ± 1.3 weeks; mean ± SD). Each individual’s legs were randomly assigned to one of four conditions: non-exercising control (CON), continuous exercise training (balanced across both MC phases; EX), high-volume in the follicular phase with low volume in the luteal phase (HV-FOL), or the converse (HV-LUT). HV was defined as five sets per exercise twice weekly (≥10 sets·muscle⁻¹·week⁻¹), and low volume comprised one set per exercise twice weekly (≤5 sets·muscle⁻¹·week⁻¹). The primary outcome was thigh lean mass via dual-energy x-ray absorptiometry. Secondary outcomes were vastus lateralis cross-sectional area (VL CSA), leg fat-free mass (FFM) via bioelectrical impedance analysis, one-repetition maximum (1RM) strength and maximal voluntary isometric contraction. Results: All RET conditions produced greater gains than CON for thigh lean mass, VL CSA, FFM, and 1RM strength (all, p < 0.001), with no differences (all, p ≥ 0.17) between any of the training conditions (EX, HV-FOL, and HV-LUT). Conclusions: MCPBT confers neither hypertrophy nor strength advantages over traditional continuous RET. Training volume-load, not MCPBT, was associated with several adaptations. MC phase-based adjustments in RET could be based on individual preference but are not necessary to achieve muscular adaptations to RET.