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.