Displacement and frequency for maximizing power output resulting from a bout of whole-body vibration

Whole-body vibration (WBV) has been shown to be effective for increasing lower-body power; however, the combination of frequency, displacement, and duration that elicits the best acute response has yet to be determined. The purpose of this study was to identify the protocol eliciting the greatest improvement in power after an acute bout of WBV. Forty men and women participated in this study, in which 8 different combinations of 30, 35, 40, and 50 Hz with 2-mm and 5-mm displacements were tested over 3 days. For all protocols, randomized to reduce potential order effects, subjects underwent 30 seconds of WBV while holding an isometric squat at a knee angle of 2.27 rad. Power was assessed by countermovement jumps. Subjects performed 3 jumps before WBV, immediately afterward, and 1, 5, and 10 minutes later. The highest normalized peak power (nPP) at each time point was determined using a 4 (frequency) x 2 (displacement) x 5 (time) repeated-measures analysis of variance. Significant effects were seen for frequency (p < or = 0.026) and time (p < or = .0001). Post hoc analyses revealed that the 30-Hz condition (1.010 +/- 0.003) produced a higher nPP than 35 Hz (1.00 +/- 0.003, p < or = 0.026) and 40 Hz (1.002 +/- 0.002, p < or = 0.028) but not 50 Hz (1.004 +/- .002). We also found a significantly higher nPP for the 1-minute post-treatment time point (1.011 +/- .0003) vs. all other time points (p < or = 0.006). Our data show that an acute WBV bout can significantly increase power output at 1 minute post-treatment across all frequencies and displacements, although 30 Hz appears to have a greater effect on power output than either 35 Hz or 40 Hz, but not 50 Hz, at all post-treatment time points.