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.
Design: 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.