The effect of 8 mos of twice-weekly low- or higher intensity whole body vibration on risk factors for postmenopausal hip fracture.

OBJECTIVE Whole body vibration is a potential therapy for age-related loss of musculoskeletal competence. Vibration has improved bone in animal models, but evidence in humans is limited. Relative efficacy of low- vs. high-intensity whole body vibration is also unknown. Our goal was to observe the effect of brief low- and higher intensity whole body vibration on risk factors for hip fracture in postmenopausal women. DESIGN We used an 8-mo randomized controlled trial design to examine the influence of twice-weekly low-intensity whole body vibration (15 mins, 30 Hz, 0.3 g) or higher intensity whole body vibration (2 × 3 mins, 12.5 Hz, 1 g) on anthropometrics, bone (whole body, hip, spine, forearm, and heel), muscle (wall squat and chair rise), and balance (tandem walk and single leg stance). Physical activity, daily calcium, and compliance were recorded. Effects were examined by repeated-measures analysis of covariance, controlling for age, height, weight, calcium, physical activity, compliance, and baseline values. RESULTS Forty-seven women (71.5 ± 9.0 yrs) completed the trial. There were no between-group differences in any measure at 8 mos, but within-group effects were evident. Controls lost bone at the trochanter (-6%, P = 0.03) and lumbar spine (-6.6%, P = 0.02), whereas whole body vibration groups did not. Whole body vibration subjects improved wall squat (up to 120%, P = 0.004) and chair rise performance (up to 10.5%, P = 0.05). CONCLUSIONS Eight mos of twice-weekly whole body vibration may reduce bone loss at the hip and spine and improve lower limb muscle function. These changes may translate to a decreased risk of falls and hip fracture.