Calcif Tissue Int. 2014 Dec;95(6):547-56.
Effect of whole-body vibration on calcaneal quantitative ultrasound measurements in postmenopausal women: a randomized controlled trial.
Slatkovska L, Beyene J, Alibhai SM, Wong Q, Sohail QZ, Cheung AM.
Osteoporosis Program, University Health Network/Mount Sinai Hospital, 200 Elizabeth Street, 7 Eaton North, Room 221, Toronto, ON, Canada.
The purpose of this study was to examine the effect of whole-body vibration (WBV) on calcaneal quantitative ultrasound (QUS) measurements; which has rarely been examined. We conducted a single-centre, 12-month, randomized controlled trial. 202 postmenopausal women with BMD T score between -1.0 and -2.5, not receiving bone medications, were asked to stand on a 0.3 g WBV platform oscillating at either 90- or 30-Hz for 20 consecutive minutes daily, or to serve as controls. Calcium and vitamin D was provided to all participants. Calcaneal broadband attenuation (BUA), speed of sound, and QUS index were obtained as pre-specified secondary endpoints at baseline and 12 months by using a Hologic Sahara Clinical Bone Sonometer. 12-months of WBV did not improve QUS parameters in any of our analyses. While most of our analyses showed no statistical differences between the WBV groups and the control group, mean calcaneal BUA decreased in the 90-Hz (-0.4 [95% CI -1.9 to 1.2] dB MHz(-1)) and 30-Hz (-0.7 [95% CI -2.3 to 0.8] dB MHz(-1)) WBV groups and increased in the control group (1.3 [95% CI 0.0-2.6] dB MHz(-1)). Decreases in BUA in the 90-, 30-Hz or combined WBV groups were statistically different from the control group in a few of the analyses including all randomized participants, as well as in analyses excluding participants who had missing QUS measurement and those who initiated hormone therapy or were <80% adherent. Although there are consistent trends, not all analyses reached statistical significance. 0.3 g WBV at 90 or 30 Hz prescribed for 20 min daily for 12 months did not improve any QUS parameters, but instead resulted in a statistically significant, yet small, decrease in calcaneal BUA in postmenopausal women in several analyses. These unexpected findings require further investigation.
Whole-body vibration involves standing upright on a platform that oscillates up-and-down or side-to-side and vibrates the body (Figure 1). Early studies of whole-body vibration in animal models, such sheep for example, have found that standing on a whole-body vibration platform leads to significant improvements in bone mineral density and microarchitecture at anatomical locations located in close proximity to the platform, which receive the vibration stimulus before it becomes dissipated by major joints and soft tissues(1). The findings in animal models have subsequently encouraged studies in humans to examine whether whole-body vibration can be used as a therapy to help minimize bone loss that occurs during menopause and aging(2).
Figure 1. Type of whole-body vibration platform that was examined in our research study.
Our research group was interested in examining whether the whole-body vibration can be used in healthy postmenopausal women who have low bone mineral density to help prevent osteoporosis. Before starting our examination, we systematically reviewed previous randomized controlled trials that examined the effect of whole-body vibration on bone in postmenopausal women (2). Four trials were found that examined bone mineral density at the lumbar spine and our meta-analysis showed no statistically significant effect of whole-body vibration after 6 to 12 months of follow-up. Further, three trials were found that examined bone mineral density at the hip, and our meta-analysis showed small improvements in response to WBV after 6 to 12 months of follow-up. However, these improvements were small and had low clinical relevance. The trials examined in our meta-analysis also had important limitations such as a small number of participants (less than 75), inadequate calcium and vitamin D intakes, and inadequate follow-up (<12 months).
With those limitations in mind, our group developed a randomized control trial that examined whole-body vibration in 202 postmenopausal women who did not have osteoporosis but had low bone mineral density(3). We examined the effects whole-body vibration over a 12-month follow-up period, during which we ensured adequate calcium and vitamin D intakes in all trial participants by assessing their average dietary intakes of calcium and vitamin D and providing daily supplementation as needed. At baseline, trial participants were randomly assigned to one of three groups: one group (n=67) received whole-body vibration platform that vibrated at 90 Hz and low magnitude (produced an acceleration of 0.3g, where 1g = approximately 10 m/s2); another group (n=68) received the same type platform that vibrated at 30 Hz and the same low magnitude; and control group (n=67) did not receive whole-body vibration platform.
The women who received the whole-body vibration platform took it home with them and were asked to stand on it every day for 20 consecutive minutes, while the controls were asked to go on with their life as usual and to not use whole-body vibration during the trial participation. At baseline, prior to randomly assigning the study participant to one of the three groups, we measured their bone mineral density at the spine (lumbar), hip (total hip and femoral neck), ankle (distal tibia) and wrist (distal radius) and their bone microarchitecture at the ankle and wrist. The gold standard – DXA (Hologic) – was used for the hip and spine measurements and the high-resolution peripheral quantitative computed tomography (HR-pQCT) was used for the ankle and wrist measurements. The primary outcome for which this trial was statistically powered was trabecular bone mineral density at the ankle(3).
The quantitative ultrasound measurements of the heel (Figure 2) – namely the broadband attenuation and speed of sound – were also collected, as secondary variables. It was hypothesized that, if an effect was found, the heel bone (calcaneus) would have been equally or more responsive to WBV than the ankle. When compared to the spine and hip, both anatomical locations – the ankle and heel – are in a close proximity to the WBV stimulus and the heel bone is also not cushioned by a major joint prior to receiving the WBV stimulus. As such, we expected to see an increase in the broadband attenuation and speed of sound at the heel, in a similar magnitude as the expected changes in bone measurements obtained at the ankle.
Figure 2. Quantitative ultrasound measurement of the heel performed in our research study.
After 12 months of follow-up, median self-reported adherence to calcium and vitamin D supplementation was 96-98% (mean 89-90%) and did not differ between the three groups. Adherence to whole-body vibration was 79 % (interquartile range 41–91 %) and 77 % (interquartile range 55–86 %) in women with 90 Hz and 30 Hz platform, respectively. All three groups experienced decreases in HR-pQCT and DXA bone measurements that were normal for healthy postmenopausal women and that did not differ between the groups, thus pointing towards WBV therapy not having an effect.
Decreases in the speed of sound of the heel bone were also found in the three groups, which were normal and similar. However, the broadband attenuation of the heel was found to decrease in women using the 90 Hz (-0.4 95% CI -1.9 to 1.2 dB MHz-1) and 30 Hz (-0.7 95% CI -2.3 to 0.8 dB MHz-1) WBV platform after 12 months of follow-up, and increase in the controls (1.3 95% CI 0.0-2.6 dB MHz-1). The decrease in broadband attenuation was statistically significant in a number of analyses (including analysis of all randomized participants and in analyses excluding participants who had missing QUS measurement and those who initiated hormone therapy or were <80% adherent), but had a small magnitude and low clinical relevance.
We concluded that since the direction of the effect of WBV on broadband attenuation of the heel bone pointed towards worsening in bone microarchitecture and/or bone mineral density in our trial of postmenopausal women, and since these results were unexpected, further investigations are needed to further explore the findings.
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- Slatkovska L, Alibhai SM, Beyene J, Cheung AM. Effect of whole-body vibration on BMD: a systematic review and meta-analysis. Osteoporosis International. 2010; 21:1969-80.
- Slatkovska L, Alibhai SM, Beyene J, Hu H, Demaras A, Cheung AM. Effect of 12 Months of Whole-Body Vibration Therapy on Bone Density and Structure in Postmenopausal Women. Annals of Internal Medicine. 2011; 155:668-679.