One session of whole body vibration increases voluntary muscle strength transiently in patients with stroke

Objective: To determine the effect of whole body vibration on isometric and eccentric torque and electromyography (EMG) variables of knee extensors on the affected side of stroke patients. D esign: A randomized controlled study. Setting: A rehabilitation centre. Subjects: Sixteen patients (age 58.2 +/- 9.4 years) were enrolled in an inpatient rehabilitation programme 27.2 +/- 10.4 days after a stroke. Interventions: Eight patients were randomly assigned to the vibration group and received 20 Hz vibration (5 mm amplitude) while standing on a vibration platform for 1 minute six times in one session. Patients in the control group also stood on the platform but did not receive vibration. Main measures: Maximum isometric and eccentric torque, rate of torque development, root-mean-squared EMG, median frequency of vastus lateralis, and co-activation of knee flexors. Results: Isometric and eccentric knee extension torque increased 36.6% and 22.2%, respectively, after vibration (P < 0.05) and 8.4% and 5.3% in the control group. Vibration increased EMG amplitude 44.9% and the median frequency in the vastus lateralis by 13.1% (all P < 0.05) without changes in the control group (10.6% and 3.9%). Vibration improved the ability to generate mechanical work during eccentric contraction (17.5%). Vibration reduced biceps femoris co-activation during isometric (8.4%, ns) and eccentric (22.5%, P < 0.05) contraction. Conclusion: These results suggest that one bout of whole body vibration can transiently increase voluntary force and muscle activation of the quadriceps muscle affected by a stroke.