Does EMG activation differ among fatigue-resistant leg muscles during dynamic whole-body vibration?
The purpose of this study was to determine the effects of dynamic whole-body vibration (WBV) stimuli on the electromyographic (EMG) responses of different fatigue-resistant leg muscles. The participants (N=32) were divided into two groups according to the Fatigue Index value [Group I: Less Fatigue Resistant (LFR), n=17; Group II: More Fatigue Resistant (MFR), n=15]. The repeated EMG activities of four leg muscles [rectus femoris, biceps femoris, vastus lateralis and vastus medialis] were analysed during WBV stimulation. The data were analysed using PASW/SPSS Statistics 18.0 and the significance level was set at p<0.05. The results revealed that the vibration frequency, amplitude and group (MFR and LFR) had a significant effect (p<0.001) on the EMG response. Dynamic WBV stimuli performed at different frequencies (30Hz, 35Hz and 40Hz) and amplitudes (2mm and 4mm) resulted in significantly increased lower-body muscular activation. However, the LFR group exhibited a significantly higher percentage increase in EMG activation at higher frequencies (max 40Hz) and amplitudes (4mm) (p≤0.001). The results could be useful for the optimal prescription of vibration exercise and can guide the development of training and rehabilitation programmes.
Key words: Fatigue; Fatigue resistance; Isokinetic; Rehabilitation; Muscle activation; Electromyography.