Abstract
[Purpose] The risk of anterior cruciate ligament injuries in females may be related to hormonal fluctuations resulting from increased laxity of muscles. The purpose of this study was to investigate variation of stiffness and shortening of femoral muscles over the course of the menstrual cycle. [Subjects and Methods] The subjects were nine healthy young women (measurements: 18 lower extremities) with regular menstrual cycles, mean age 25.9 ± 2.1 years. Measurements were performed during the periods of menstrual, ovulation, early luteal and late luteal in a menstrual cycle. Muscle stiffness of rectus femoris and biceps femoris was measured using a muscle hardness meter. Muscle shortening of rectus femoris and hamstrings was measured using a goniometer. [Results] Muscle stiffness of the belly region of rectus femoris and biceps femoris was significantly higher during the early luteal period than the other periods (p<0.05). However, muscle shortening did not change. [Conclusion] The results suggest that muscle stiffness of femoral muscles changes during regular menstrual cycles.
