The interaction between body position and vibration frequency on acute response to whole body vibration.

PURPOSE: The present study was designed to investigate the electromyographic (EMG) response in leg muscles to whole-body vibration while using different body positions and vibration frequencies. METHODS: Twenty male sport sciences students voluntarily participated in this single-group, repeated-measures study in which EMG data from the vastus lateralis (VL) and the lateral gastrocnemius (LG) were collected over a total of 36 trials for each subject (4 static positions × 9 frequencies). RESULTS: We found that vibration frequency, body position and the muscle stimulated had a significant effect (P-values ranged from 0.001 to 0.031) on the EMG response. Similarly, the muscle × frequency and position × muscle interactions were significant (P < 0.001). Interestingly, the frequency × positions interactions were not significant (P > 0.05). CONCLUSIONS: Our results indicate that lower frequencies of vibration (25-35 Hz) result in maximal activation of LG, whereas higher frequencies (45-55 Hz) elicit the highest responses in the VL. In addition, the position P2 (half squat position with the heels raised) is beneficial both for VL and LG, independently of the vibration frequency.