Analysis of the Obturatorius Muscle Activity Using Magnetic Resonance Imaging

[Purpose] The purpose of this study was to demonstrate the amount of load that best facilitates the measurement of obturatorius muscle activity by MRI. [Subjects] Eleven healthy males participated in this study. [Methods] The obturatorius internus, the obturatorius externus, the gluteus maximus, the gluteus medius and the sartorius muscles were examined using MRI. The MR signal intensity was compared before and after two different concentric isokinetic hip external rotation exercises: high load at 60°/sec and no load at 500°/sec. [Results] In the 60°/sec exercise, the signal intensities of the obturatorius internus, the obturatorius externus, the gluteus medius and the sartorius muscles were significantly higher after the exercise than before the exercise. In the 500°/sec exercise, the signal intensities of the obturatorius internus, the obturatorius externus and the sartorius muscles were significantly higher after the exercise than before the exercise. [Conclusion] Slow angular velocity isokinetic exercise with high load as well as no-load rapid angular velocity isokinetic exercise is effective at eliciting activity of the obturatorius muscle.