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

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, I-2=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. (C) 2020 Sports Medicine Australia. Published by Elsevier Ltd. All rights reserved.