Variations in strength-related measures during the menstrual cycle in eumenorrheic women: A systematic review and meta-analysis

Abstract Objectives To systematically review the current body of research that has investigated changes in strength-related variables during different phases of the menstrual cycle in eumenorrheic women. Design Systematic review and meta-analysis. Methods A literature search was conducted in Pubmed, SPORTDiscus and Web of Science using search terms related to the menstrual cycle and strength-related measures. Two reviewers reached consensus that 21 studies met the criteria for inclusion. Methodological rigour was assessed using the Quality Assessment Tool for Observational Cohort and Cross-Sectional Studies. Random effects meta-analyses were used to compare the early-follicular, ovulatory and mid-luteal phases for maximal voluntary contraction, isokinetic peak torque, and explosive strength. Results The assessment of study quality showed that a high level of bias exists in specific areas of study design. Non-significant and small or trivial effect sizes (p ≥ 0.26, Hedges g ≤ 0.35) were identified for all strength-related variables in each comparison between phases. 95% confidence intervals for each comparison suggested the uncertainty associated with each estimate extends to a small effect on strength performance with unclear direction (−0.42 ≤ g ≤ 0.48). The heterogeneity for each comparison was also small (p ≥ 0.83, I2 = 0%). Conclusions Strength-related measures appear to be minimally altered (g ≤ 0.35) by the fluctuations in ovarian sex hormones that occur during the menstrual cycle. This finding should be interpreted with caution due to the methodological shortcomings identified by the quality assessment.