Some time ago I found, on the inside front cover of my favourite physiotherapy journal, the image of an elderly woman sitting, legs outstretched, with her calves resting on a device advertised to improve circulation using vibration. My first step was to ‘Google’ it. It appeared from this simple search that WBV was the answer to all your health needs; improving circulation, strength, energy, coordination, flexibility, and agility. Www.wholebodyvibration.ca reported that WBV improved health and well being and reduced pain, stress, fatigue, stress hormones and even fat and cellulite. Wikipedia wrote that in the short term, WBV stimulated muscle fibre contraction at a faster than normal rate thereby increasing circulation and increasing force production. In the longer term, the online encyclopedia quoted research claiming WBV improves bone mineral density and optimizes strength training. This seemed too good to be true but the research references definitely warranted a visit to PubMed so I carefully searched for articles on the topic. Searching ‘whole body vibration’ limited to human clinical trials among people with neurological disorders completed in the last 5 years, I found 14 articles. This review is not intended to be a systematic or comprehensive review of WBV, but a discussion of current evidence examining the usefulness of WBV as a therapeutic intervention in neurological disorders.
Background: WBV and Athletic training
WBV is often combined with other exercises such as 30 second hold while in squat or lunge position; usually 3 times per week for 4 to 8 weeks. The vibration frequency, pattern (vertical or reciprocal), and amplitude vary within limits set by the particular machine. Recent well-controlled studies examining holding squat exercises with and without WBV in young adults (Corme 2006, Kvorney 2006) and older volunteers (Rees 2008, Bograts 2007) demonstrate that WBV training has no additional benefit on power of major lower extremity muscle groups compared to training alone (same exercises but with vibration platform turned off). Furthermore, WBV does not change thigh muscle oxygenation (amount of oxygen carried by the blood cells in the arteries within the muscle Cardinale 2007) or alter serum levels of testosterone or the trophic factor IGF-I (Cardinale 2006); nor does WBV with exercise enhance oxygen uptake over exercise alone in older and younger community dwelling volunteers (Cochrane 2008). Although WBV combined with static exercise increases perceived exertion, heart rate is not different between WBV with exercise and exercise alone (Cardinale 2007). This suggests that even though subjects perceive they work harder with WBV, their body’s indicators don’t show that. Not all studies have negative results however. WBV is superior to traditional stretching techniques in improving hamstring flexibility (Van den Tillan 2006) and WBV enhances thigh muscle strength in very weak subjects (Savelberg 2007). Overall these studies suggest that although WBV appears to improve strength, the additional benefits over traditional strength training are modest.
WBV and Parkinson’s disease
Three studies have examined WBV to reduce tremor, stiffness and improve balance in people with Parkinson’s disease (PD). In a well-planned study of 68 people with PD following 5 episodes of 1 minute variable frequency vibration, Haas (Neurorehab 2006) reported a significant (5 point) reduction in symptom severity score following WBV compared to a no intervention control. Biggest improvements were in tremor and stiffness scores but also in speed of movement and walking and posture scores up to 3 hours afterwards. WBV does not appear to improve balance when compared to conventional balance training using a wobble board or uneven surface practice (Ebersbach 2008) or walking (Turbanski 2005) in people with PD. In another study of 52 people with PD, Turbanski (2005) and colleagues measured balance using a computerized balance platform after 15 minutes of WBV or 15 minutes of indoor walking. Both groups had improved performance in narrow standing with the WBV group having additional improvement in balance with even narrower stance.
These studies suggest that WBV has a beneficial effect, in at least the short term, on some symptoms of Parkinson ’s disease and it is just as good as usual balance training to improve balance. It is probably better than doing nothing at all.
WBV in stroke rehabilitation
In a small study of 18 people, 15 to 50 days post-stroke, Tihanyi (2007) reported that WBV (1 min followed by 1 min rest six times) enhanced thigh muscle strength compared to simply standing on the WBV (without vibration). The study did not evaluate subjects beyond the immediate post-treatment phase so duration of the effect is not known. A larger well-controlled trial of WBV among 53 people at least 6 weeks post-stroke (Van Nees & Latour 2006) studied WBV or music/exercise therapy added to regular inpatient rehabilitation. Subjects had 30 minutes of either WBV or music and exercise group therapy, 5 days per week for 6 weeks with equal amounts of therapist contact. Both groups had equal gains in balance and function which was maintained at 6 week follow-up. WBV was just as effective as music/exercise therapy in combination with inpatient rehabilitation. Furthermore, there were no accidents or more participant drop-outs in the WBV group suggesting it was probably safe.
WBV to treat MS symptoms
In one small trial among 12 people with multiple sclerosis (MS) (Schunfield 2005), subjects received one treatment of WBV or a nerve stimulation treatment (one minute with one minute rest, 5 times) and were evaluated immediately and one week afterwards. Speed of getting up and walking 10 feet decreased by one second in the WBV group compared to the nerve stimulation group at the follow-up. Computerized balance testing examining sway and response to being put off balance showed no difference between the two interventions. At least in the articles searched in the past 5 years, there is no evidence yet to suggest that WBV in people with MS improves symptoms.
Is WBV harmful?
My PubMed search led me to a number of articles discussing occupational heath and safety in jobs in which workers (e.g. truck drivers, factory workers) are exposed to vibration. Occupational vibration is proposed to accelerate spinal joint and disc deterioration, hearing loss, and balance impairment. Abercrombie (2007) reports that the estimated vibration dose value of 17 is considered the upper limit of safe exposure. These researchers measured head and spine vibration during typical WBV treatment and they concluded that the transmitted forces through the head and spine are lessened when the knees are kept bent, suggesting positioning in a deep squat is important. These researchers also report that the acceptable limits of vibration exposure are exceeded during both vertical and reciprocal vibration (although reciprocal was less) and they recommend reciprocal (they term rotational) vibration with the knees flexed for durations less than 10 minutes in short bursts. This study points out that WBV may not be safe for everyone and WBV could worsen some conditions such as joint pain.
Evidence seems to be growing that WBV as a specific intervention can improve bone density, muscle mass and peripheral circulation (not described here). Intuitively, one can imagine the usefulness of such an intervention, however, the studies performed thus far were mainly in healthy individuals and there are few studies completed in people with health conditions. In people with Parkinson’s disease, WBV is as good as a traditional exercise program to improve balance and may be of additional benefit in the short term to reduce symptoms like tremor and slowness of movement. Overall, the findings to support WBV intervention as a method to increase strength and balance are not compelling when comparing to an equivalent intervention with matched therapist contact. However, WBV can be considered better than no treatment all. There has been very little research around safety of WBV and most intervention studies excluded individuals with bone, joint, metabolic, and vascular problems, so we really don’t know the effect of WBV on people with these conditions.
So is WBV hype or a real shake-up? For my population of patients (older people with neurological problems along with multiple other health problems), WBV is not an intervention I would choose based on the evidence thus far. An equivalent amount of therapist-guided conventional cardiovascular, strength, balance, and flexibility training probably has broader benefits. However, future work on the effect of vibration on bone density, peripheral circulation and spasticity will be intriguing.