Phase-Specific Variations in Lower-Limb Muscle Strength Across the Menstrual Cycle in Female Soccer Players

Fluctuations in ovarian hormones across the menstrual cycle (MC) have been suggested to influence neuromuscular performance in female athletes. However, phase-specific variations in lower-limb muscle strength remain underexplored, particularly within the soccer population. This study investigated phase-related differences in lower-limb muscle strength across MC phases in female soccer players. A repeated-measures design was employed involving 50 competitive female soccer players. Bilateral lower-limb muscle strength was assessed using a handheld dynamometer (VALD DynaMo Plus) during the three MC phases: menstruation, late follicular, and luteal phase. Estimated menstrual cycle phases were identified using calendar-estimated tracking or an MC monitoring application (FitrWoman). Phase-related differences were analysed using repeated-measures analysis of variance with Bonferroni-adjusted post hoc comparisons, and effect sizes were reported as partial eta squared (ηp²). Significant differences in lower-limb muscle strength were observed across estimated MC phases (p < 0.05, ηp² = 0.12-0.31). Both the non-dominant and dominant limbs demonstrated higher strength values during the late follicular phase, with hip abductors emerging as the strongest muscle group bilaterally (≈149 ± 37 kg). Most muscle groups exhibited lower strength values during the menstruation phase. Lower-limb muscle strength appears to vary across calendar-estimated MC phases in female soccer players, with higher strength values observed during the late follicular phase and lower values during menstruation. These findings should be interpreted with caution due to the method of phase identification but may have implications for the scheduling of strength assessments and training load management in female athletes.