Acute effect of whole-body vibration at optimal frequency on muscle power output of the lower limbs in older women.

OBJECTIVE: The aim of this study was to identify the frequency of whole-body vibration (WBV) that elicits the greatest improvement in lower limb power output after an acute exposure in older women, with the hypothesis that an individualized optimal vibration frequency (OVF) would be more effective than a fixed vibration frequency.

DESIGN: Maximal power output was measured during a double leg press on an isoinertial dynamometer in nine women with a mean (SD) age of 71 (3) yrs, 1 and 5 mins after WBV on a platform at three different frequencies, in a random order: 20 Hz, 50 Hz, and OVF, determined for each subject by identifying the frequency corresponding to the maximal electromyographic muscle response.

RESULTS: The mean (SD) OVF was 33 (2.5) Hz. The 25.9% increase in maximal power output after 1 min of WBV at OVF was significantly higher (P < 0.05) than the 14.3% increase after 1 min of WBV at 20 Hz. Similarly, the 32.1% increase in maximal power output after 5 mins of WBV at OVF was significantly higher (P < 0.01) than the 16.1% and 16.3% increase after 5 mins of WBV at 20 Hz and 50 Hz, respectively.

CONCLUSIONS: Frequency of WBV should be prescribed in an individualized fashion, within the range of 30-35 Hz in this target population of older women.