Menstrual cycle variation and gender difference in muscle stiffness of triceps surae.

BACKGROUND

We aimed to investigate the menstrual cycle variation and the gender difference of the triceps surae muscle stiffness and passive stiffness of the ankle joint.

METHODS

The subjects of the study included 12 healthy young women and 12 healthy young men. Shear elastic moduli of the lateral gastrocnemius, medial gastrocnemius, and soleus muscles were measured as an index of muscle stiffness using shear wave elastography. The passive stiffness of the ankle joint was calculated from passive torque when the ankle joint was passively dorsiflexed. Measurements were conducted in the follicular, ovulatory, and luteal phases to examine the menstrual cycle variation.

FINDINGS: There was no difference noted in the passive stiffness or triceps surae muscle stiffness for young women in the menstrual cycle. As for gender differences, passive stiffness in all menstrual phases in women was lower while the soleus muscle stiffness in women was higher, compared to that in men.

INTERPRETATION: Our findings suggest that passive stiffness and muscle stiffness did not differ in the menstrual cycle. In addition, the measured part of the soleus was more tensioned in women than in men.