Author(s): DSOUZA, A., VAN EVERY, D., BHINDER, A., ELANGO, S., LAMONT, G., LEES, M., LIM, C., MCKENDRY, J., NEWBOLD, J., NAPHIN, C., REBALKA, I., ROXBURGH, L., SUTHRAJAN, A., WILSON, B., PHILLIPS, S., Institution: MCMASTER UNIVERSITY, Country: CANADA, Abstract-ID: 484

INTRODUCTION:
Resistance exercise training (RET) induces skeletal muscle hypertrophy and strength gains. In women, cyclic fluctuations in estradiol and progesterone across the menstrual cycle have been hypothesized to influence anabolic and catabolic signaling and thereby modulate RET adaptations. Despite growing interest in menstrual cycle-based training prescriptions, evidence is inconsistent, largely due to inadequate hormonal confirmation and poor control of RET training volume. We aimed to determine whether menstrual cycle phase-specific manipulation of training volume enhances muscle hypertrophy and strength. Aligning with proposed paradigms, we hypothesized that follicular phase-emphasized (greater volume) would enhance RET-induced adaptation.
METHODS:
Twenty-four healthy, eumenorrheic women completed a within-participant, unilateral resistance training intervention across three consecutive menstrual cycles. Menstrual cycle phase was prospectively tracked and confirmed with blood and urine measures. Each leg was allocated to one of four conditions: non-exercising control (CON), continuous training with equal volume across phases (EX), high-volume training in the follicular phase and low volume in the luteal phase (HV-FOL), or high-volume training in the luteal phase and low volume in the follicular phase (HV-LUT). High volume consisted of five sets per exercise performed twice weekly (≥10 sets per muscle per week), and low volume consisted of one set per exercise twice weekly (≤5 sets per muscle per week). Primary outcomes were thigh lean mass (DXA), vastus lateralis cross-sectional area (ultrasound), fat-free mass (bioelectrical impedance), and muscle fiber cross-sectional area. Secondary outcomes included one-repetition maximum (1RM) leg press and leg extension strength and maximal voluntary isometric contraction.
RESULTS:
All training conditions elicited greater increases in thigh lean mass, muscle cross-sectional area, fat-free mass, and 1RM strength compared with CON (all p<0.001). No differences were detected between EX, HV-FOL, and HV-LUT for any hypertrophy or strength outcome (all p>0.17 ).
CONCLUSION:
When menstrual cycle phase is rigorously confirmed and RET volume is matched, phase-based manipulation of training volume does not affect muscle hypertrophy or strength compared with continuous RET. These findings demonstrate that training volume-load, rather than menstrual cycle timing and emphasis on follicular phase heavy loading, is the primary determinant of RET-induced muscular adaptation in eumenorrheic women. Menstrual cycle-based programming may support individual preference but is not required to maximize RET outcomes.