Muscle strength and endurance do not significantly vary across 3 phases of the menstrual cycle in moderately active premenopausal women

Objective: To investigate muscle strength and muscle endurance in women during 3 well-determined phases of the menstrual cycle: early follicular phase, ovulation phase, and mid-luteal phase. Design: Prospective, within-woman analysis was performed of muscle strength and muscle endurance by repeated measures analysis of variance in 3 hormonally verified phases of 2 consecutive menstrual cycles. Participants: Fifteen female subjects with moderate physical activity level and regular menstrual cycles volunteered to participate in the study. Analyses are based on 10 subjects who completed 2 consecutive menstrual cycles with hormonally verified phases. Main Outcome Measurements: Handgrip strength, 1-leg hop test, isokinetic muscle strength, and muscle endurance were measured in 2 consecutive menstrual cycles in the early follicular phase, in the ovulation phase, and in the midluteal phase. Isokinetic muscle strength and endurance were tested with knee extension exercise on a standard instrument. Menstrual cycle phases were determined by analysis of sex hormone levels in serum, and ovulation was detected by luteinizing hormone surge in urine. Results: No significant variation in muscle strength or muscle endurance could be detected during different well-determined phases of the menstrual cycle. Conclusions: This study detected no significant variation in muscle strength and muscle endurance during the menstrual cycle. In contrast to other studies showing variations in strength and endurance during the menstrual cycle, the present study was hormonally validated and was repeated in 2 consecutive menstrual cycles. However, it is unknown whether these data in moderately active university students would be relevant to the highly trained woman athlete.