The Effect of Menstrual-Cycle Phase on Hamstring Extensibility and Muscle Stiffness

Abstract

Context:Preventing noncontact ACL injuries has been a major focus of athletic trainers and researchers. One factor that may influence female noncontact ACL injury is the fluctuating concentrations of hormones in the body.Objective:To determine whether muscle properties change across the menstrual cycle.Design:Repeated measures. Testing was performed within 3 d after the onset of menses and ovulation. Repeated-measures ANOVAs were used to determine changes in variables across the menstrual cycle, and Pearson correlations were used to determine relationships between variables.Participants:8 women with normal menstrual cycles.Main Outcome Measures:Active hamstring stiffness and hamstring extensibility.Results:Hamstring extensibility (P = .003) increased at the ovulation testing session but hamstring muscle stiffness (P = .66) did not.Conclusions:The results indicate that hamstring muscle stiffness did not change across the menstrual cycle and hamstring extensibility increased at ovulation, when estrogen concentration increases.