Abstract
[Purpose] To analyze differences in action between fibers of the gluteus medius. [Subjects and Methods] The subjects were healthy males aged 22–34 years. The motor task was 30% maximum voluntary isometric hip abduction contraction in different directions (1, abduction; 2, abduction + flexion; 3, abduction + extension). Muscle thickness and distance of the muscle–tendon junction were measured using ultrasonography, and their rates of change were calculated. [Results] The rate of change in muscle thickness of the anterior and posterior gluteus medius was significantly higher in tasks 2 and 3, respectively. The rate of change in the distance of the muscle–tendon junction was the same as the rate of change in muscle thickness. [Conclusion] Anterior gluteus medius fibers participate in flexion in addition to abduction, and posterior gluteus medius fibers participate in extension in addition to abduction.
