RESUMEN
PURPOSE: This study aimed to determine the appropriate stimulus strength that could result in a positive effect on the ankle joint spasticity when patients with chronic stroke performed whole body vibration (WBV) exercise. METHODS: Among 72 patients who were diagnosed with stroke at least 6 months ago, those able to perform a half squat pose with ambulation issues due to ankle joint spasticity (modified Ashworth scale, MAS≥2) were included for analysis. Individuals participated in four different frequencies of vertical WBV exercise; 0 Hz, 10 Hz, 20 Hz, and 30 Hz. Vibration amplitude was 3-4 mm and 5 minutes WBV exercise was performed at each frequency, followed by a measurement after 2-minute rest. We assigned 18 individuals to each frequency and asked them to participate in the WBV exercise once every 3 weeks. The level of spasticity was evaluated by visual analogue scale (VAS) for self-assessment. The myoton PRO was utilized to objectively evaluate the level of spasticity and check the muscle tone and stiffness. RESULTS: Participants showed 0 Hz VAS was a significant difference between 20 Hz application conditions (p < 0.05). Muscle tone was significantly different at 0 Hz between 20 Hz, and 30 Hz (p < 0.05), significantly difference at 10 Hz between 30 Hz (p < 0.05). Muscle stiffness significantly difference at 0 Hz between 20 Hz, and 30 Hz (p < 0.05), significantly difference at 10 Hz between 20 Hz, and 30 Hz (p < 0.05). CONCLUSION: Findings of this study show that the frequency of more than 20 Hz was effective in improving the ambulatory ability in patients with chronic stroke. Currently, the effective WBV protocol is limited. Hence, this study was designed to suggest an effective WBV protocol to improve neuromodulation ability for chronic stroke patients.