Abstract : AIM: To compare muscle activity of lower limb muscles between dual mode whole-body vibration (WBV) and the commonly used side-alternating mode.
METHODS: Thirty physically active volunteers performed static squats at a knee angle of 60° (0°: knee fully extended) on the WBV platform while surface electromyography (sEMG) was measured of the vastus lateralis (VL), the biceps femoris (BF), and the soleus (SOL). The side-alternating WBV trial was induced at a frequency of 6Hz and an amplitude (displacement from baseline to peak) of 2.5mm. Dual mode WBV consisted of side-alternating vibration with additional circular vibration in the horizontal plane with frequencies of 14Hz and 43Hz. Root mean square of the sEMG signals (sEMGRMS) was calculated after withdrawal of the excessive spikes in the sEMG spectrum via linear interpolation. Then, sEMGRMS was normalized to the sEMGRMS during maximal voluntary contractions (MVCs). Finally, sEMGRMS during a control trial without vibration was subtracted from the trials with WBV in order to isolate the increase in muscle activity due to the vibration.
RESULTS: Increase in sEMGRMS of the VL and BF was significantly greater during dual mode compared to side-alternating WBV when the dual mode trial consisted of the high circular frequency (43Hz, P < 0.01, Figure 1). In the SOL, the dual mode enhanced muscle activity significantly compared to the side-alternating mode for both circular vibration frequencies (14Hz, 43Hz, P < 0.01, Figure 1).
CONCLUSION: Dual mode WBV resulted in significantly higher muscle activity in select lower limb muscles than the commonly used side-alternating mode. Therefore, it is recommended that dual mode platforms be considered for future WBV protocols in order to optimize the training stimulus in the lower limbs.