The Effect of a 9 Month Whole Body Vibration Program at Two Different Intensities on Bone Mineral Density in Women

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Bone loss resulting in osteoporosis is a major problem for postmenopausal women who have approximately a 50% chance of being diagnosed with this disease. Whole body vibration (WBV) has been used as an alternative mode of exercise to increase muscular strength and bone mineral density (BMD) but research on the intensity of vibration needed is lacking. PURPOSE: To examine the effects of utilizing WBV training at two different intensities on bone mineral density and body composition in women with low BMD. METHODS: The final sample for the study consisted of 27 sedentary women (age: 62.2 ± 6.0 yr, weight: 71.7 ± 12.7 kg, and lean mass: 38.4 ± 4.3 kg). Participants were randomly divided into one of three groups: control (CON; n = 9), low-intensity vibration (LI; n = 13), and high-intensity vibration (HI; n = 5). The two treatment groups participated in a 9-month WBV program 3 times/ wk, with monthly increases in duration and intensity. The control group was instructed to not change their physical activity habits. Bone mineral density and body composition were assessed with DXA (Lunar Prodigy). All participants completed an isometric strength assessment on the Biodex. A 3 x 2 (treatment x time) repeated measures MANOVA was used to analyze the data with level of significance set at.05. RESULTS: No significant changes in BMD or body composition were found for any group. Percent changes in lumbar spine and femoral neck BMD were 4.8% and 3.6% for HI, 0.5% and 1.7% for LI, and 1.5% and 0.4% for CON, respectively. Leg extension strength had a significant 23% increase (p =.012) for the HI group and a significant 11.1% decrease (p =.015) for the CON group while the LI group change (-7.1%) was not significant. Changes in leg flexion strength (18.9%, -6.5%, -5.6%, for HI, LI, and CON respectively) followed a similar pattern but were not significant. CONCLUSION: Based on our findings, WBV did elicit significant increases in isometric strength, but only in the HI group. There were no significant changes in BMD in women with low bone mass, though small sample size could have precluded finding significant differences. Supported by Texas Woman's University Multidisciplinary Research Program.