Effect of muscle vibration on postural balance of Parkinson's diseases patients in bipedal quiet standing.

[Purpose] The purpose of this study was to investigate the effect of muscle vibration applied to the lower extremities on static postural balance of patients with Parkinson's disease (PD). [Subjects] Seven subjects with Parkinson's disease participated in this study. [Methods] The oscillators of vibration were attached to the muscle bellies of the tibialis anterior, gastrocnemius, biceps femoris, and rectus femoris on both sides of the lower extremities with adhesive tape. A vibration frequency of 60 Hz was used to induce static postural reactions. Subjects' center of pressure (COP) sway and peak ground reaction force (GRF) were measured with their eyes open with and without vibration. COP sway and peak GRF (Fx, Fy, Fz) were measured using a force plate (AMTI, Newton, USA), which provides x, y and z coordinates of body movement. [Results] The area of COP sway with vibration was significantly smaller than that with no vibration, but the length of COP sway showed no difference between two conditions. Peak medial-lateral maximum force (Fy) with vibration was significantly higher than that with no vibration, but peak anterior-posterior force (Fx) and peak vertical force (Fz) showed no differences. [Conclusion] These results suggest that vibration applied to the lower extremities can help PD patients control postural balance during quiet standing.