Efficacy of whole-body vibration training on musculoskeletal health and falls risk in frail older people

The personal and social consequences of poor mobility and injuries sustained during falls in older people are a major public health concern. As the proportion of older people in the UK rises, this public health issue will become increasingly relevant. Whole-body vibration (WBV) training has the potential to improve postural stability, muscular power and bone health and hence potentially reduce loss of mobility and risk of falls and fractures. It is thus timely to evaluate potential benefits in older people and given the potential detrimental effects of vibration, it is also important to evaluate any risks in this population. To date the efficacy of WBV training has not been established in community dwelling frail older people and appropriate standards or the best WBV training protocol have not been established for any segment of the population. The vibration ‘dose’ of seven WBV training devices was determined according to statutory guidelines designed to minimise occupational vibration exposure. There was an extensive range of vibration available on these devices (frequency weighted r.m.s. acceleration in the vertical axis between 0.23 m/s2 to 22.64 m/s2). Two devices were selected, one with a tilting and one with a vertical motion to evaluate the human response to WBV training. Short periods (8 x 30s) of WBV training at magnitudes of 1.68 to 59.85 m/s² r.m.s. acceleration (1.66 to 12.11 m/s² frequency weighted), between 5 and 39 Hz, though intense, was acceptable for healthy men and women between 22 and 83 years of age. Increasing magnitude resulted in increasing perception of intensity however 5 Hz produced the greatest perception of intensity per magnitude of vibration. Frequency weighted acceleration was a useful predictor of subjective intensity of WBV training for tilting and vertical WBV training. Using the conclusions drawn from the previous two studies appropriate WBV training protocols were selected for a randomised controlled intervention study in a clinical setting. 104 patients referred to Nottingham University Hospitals NHS Trust for a falls prevention programme were invited to take part, 61 of whom were eligible and agreed to participate. The participants aged between 64 and 95 years old were randomly allocated to Control, Tilting or Vertical WBV training groups. In addition to usual care, which included an exercise programme designed to reduce the risk of falls, all participants stood in a half squat position for up to 6 x 1 min bouts 3 times a week for 12 weeks on a tilting (Galileo; 29.8 Hz, 36.0 m/s2 r.m.s), vertical (Next Generation Power Plate; 28.4 Hz, 15.3 m/s2 r.m.s) or stationary (low frequency noise during bouts as a placebo) WBV training platform. 12 weeks of tilting or vertical WBV training was well tolerated and no serious adverse affects were reported in this population of frail older people. There were no additional symptoms or shifts in tactile sensitivity of the feet, compared with standing on a stationary platform. In comparison to the Control group improvements in leg power, jump height and bone metabolism profile (increased P1NP) were observed in the combined tilting and vertical WBV training groups. There were no between group differences in measures of functional mobility and balance [Timed Up and Go (TUG) time, chair stand test, four stage balance test, functional reach, Four Square Step Test (FSST) time, postural sway], fear of falling (FES), ability to carry out activities of daily living (NEADL), physical activity (PASE) or general health and well being (SF 36). This study was unique in showing that the addition of WBV training to an existing falls prevention programme had a beneficial effect on measures of lower leg power and bone formation. Despite this the addition of WBV training did not add any additional benefit to the current falls prevention programme in functional measures previously associated with an increased risk of falling in older people. In the same population of frail older people a single session of WBV training (combined Tilting and Vertical WBV training groups) elicited an acute increase in muscular performance (knee extensor power and jump height), and no difference in static balance compared with standing on a stationary device (Control group). Having found that the addition of either tilting or vertical WBV training improves aspects of musculoskeletal health in frail older people undertaking a falls prevention programme further research including fall and fracture incidence, bone density and structure and rate of force development may be beneficial. Due to the enormous range of vibration delivered and since not all devices delivered vibration indicated by the settings it is recommended that future studies report not only platform settings but measured frequencies, magnitudes (unweighted and weighted), direction and waveforms.