The present study aimed to investigate the changes in the mechanical and metabolic properties of human muscle and tendon during the menstrual cycle in vivo. The subjects were young healthy women (n = 8, age 22.5±0.9 years) with a normal menstrual cycle. Cycle phases were divided into the menstrual, (when estradiol and progesterone concentrations were low) ovulatory (when estradiol was elevatated and progesterone was low), and luteal (when progesterone was elevated). Measurements included maximal isometric voluntary contraction (MVC), muscle thickness (using ultrasonography), muscle activation level (using interpolated twitch method) , tendon stiffness (using ultrasonography), blood volume and oxygenation of muscle and tendon (using nearinfrared spectroscopy) in knee extensors and plantar flexors. No significant changes in MVC, muscle thickness and activation level during the menstrual cycle. Similarly, there were no significant differences in the tendon properties (maximal tendon elongation and stiffness) among the three phases. These results suggested that the changes in female steroid hormones during the menstrual cycle did not affect the mechanical and metabolic properties of human muscle and tendon.

DESCENTE SPORTS SCIENCE Vol.29/THE DESCENTE AND ISHIMOTO MEMORIAL FOUNDATION FOR THE PROMOTION SPORTS SCIENCE