No Influence of Menstrual Cycle on Muscle Strength and Flexibility in Women Practising Strength Training

Background. The menstrual cycle (MC) is a natural process of the female reproductive system, characterized by fluctuations in the hormones estrogen and progesterone, which can affect physical performance, particularly strength and flexibility. Objective. To analyze the influence of the MC on muscle strength and flexibility in individuals practicing strength training, identifying variations throughout the different phases of the cycle. Methods. An exploratory study included 15 amenorrheic university students (22.50 ± 5.11 years) practicing strength training for at least 6 months, with a minimum of 3 weekly sessions. Participants with uncertain MC regularity, athletes, or those missing assessments were excluded. Sociodemographic, gynecological questionnaires, and the Menstrual Distress Questionnaire (MDQ) were administered. Muscle strength was measured via the 1-RM test for upper and lower limbs; flexibility by range of motion (goniometry) and the sit-and-reach test; subjective perception of exertion was recorded. Data were analyzed using ANOVA (p < 0.05). Results. A significant difference was observed (p = 0.001) only in menstrual symptoms, with higher values during the menstrual phase and lower values in the postmenstrual phase (beta: 120%). No significant differences were found in the other variables between the phases of the MC. Conclusions. This study found no significant differences in flexibility or muscle strength across MC phases. Despite more intense symptoms during menstruation, physical performance was unaffected. Future research should explore the relationship between the MC and physical performance in women, especially in strength training.