Acute effects of whole-body vibration on spinal excitability level and ankle plantar flexion spasticity in post-stroke individuals: A randomized controlled trial

IntroductionThis study aimed to evaluate the acute effects (up to 30 min) of whole-body vibration (WBV) on spinal excitability level and ankle plantar flexion spasticity in chronic stroke subjects.MethodsTwenty-one subjects (age 30–70 years old) with chronic stroke and ankle plantar flexion spasticity were randomly assigned to the vibration group (VG, n = 11) or the control group (CG, n = 10). Subjects in the VG underwent 10 minutes of WBV with a frequency of 35 Hz and amplitude of 2 mm. Subjects in the CG remained on the platform for 10 min without receiving vibratory stimulus. The spinal excitability level was estimated by the Hmax/Mmax ratio extracted from the H-reflex with simple stimulus examination. The value of the second/first wave ratio (H2/H1 ratio) at the peak of the first facilitation was also considered through the recovery curve with double stimulation. Spasticity was estimated by the Modified Ashworth Scale (MAS) and global perception of change. All outcomes were assessed before and at 10, 20, and 30 min after the WBV, except for MAS, which was evaluated only 10 min after WBV.ResultsNo between-group differences were found in either the spinal excitability level or plantar flexor spasticity at the three evaluated moments after WBV.ConclusionThese results suggest that WBV does not reduce spinal excitability level or spasticity of the plantar flexor muscles in chronic stroke patients in the first 30 min after vibratory stimulus.