Effects of Intensive Whole-body Vibration Training on Muscle Strength and Balance in Adults with Chronic Stroke: a Randomized Controlled Pilot Study

Objectives: To investigate the effects of a 6-week whole body vibration (WBV) training program in patients with chronic stroke.

Design: Randomized controlled pilot trial with 6 weeks' follow-up.

Setting: University hospital.

Participants: Adults with chronic stroke (N=15) were randomly assigned to an intervention (n=7) or a control group (n=8).

Interventions: Supervised, intensive WBV training. The vibration group performed a variety of static and dynamic squat exercises on a vibration platform with vibration amplitudes of 1.7 and 2.5mm and frequencies of 35 and 40Hz. The vibration lasted 30 to 60 seconds, with 5 to 17 repetitions per exercise 3 times weekly for 6 weeks. Participants in the control group continued their usual activities and were not involved in any additional training program.

Main Outcome Measures: The primary outcome variable was the isometric and isokinetic muscle strength of the quadriceps (isokinetic dynamometer). Additionally, hamstrings muscle strength, static and dynamic postural control (dynamic posturography), and muscle spasticity (Ashworth Scale) were assessed.

Results: Compliance with the vibration intervention was excellent, and the participants completed all 18 training sessions. Vibration frequencies of both 35 and 40Hz were well tolerated by the patients, and no adverse effects resulting from the vibration were noted. Overall, the effect of intensive WBV intervention resulted in significant between-group differences in favor of the vibration group only in isometric knee extension strength (knee angle, 60°) (P=.022) after 6 weeks of intervention and in isokinetic knee extension strength (velocity, 240°/s) after a 6-week follow-up period (P=.005), both for the paretic leg. Postural control improved after 6 weeks of vibration in the intervention group when the patients had normal vision and a sway-referenced support surface (P<.05). Muscle spasticity was not affected by vibration (P>.05).

Conclusions: These preliminary results suggest that intensive WBV might potentially be a safe and feasible way to increase some aspect of lower limb muscle strength and postural control in adults with chronic stroke. Further studies should focus on evaluating how the training protocol should be administered to achieve the best possible outcome, as well as comparing this training protocol to other interventions.