Author(s): NAM, H., WANG, L., Institution: SHANGHAI UNIVERSITY OF SPORT, Country: CHINA, Abstract-ID: 1215

INTRODUCTION:
The effects of whole-body vibration (WBV) training are known to be influenced by multiple parameters. Optimizing these parameters is crucial for maximizing WBV’s effectiveness in training and rehabilitation. This study examined how different vibration frequencies and loading conditions affect the electromyographic (EMG) activity of 11 lower limb muscles, providing a more comprehensive understanding of neuromuscular responses to WBV.
METHODS:
Twenty-five healthy male participants performed dynamic squats during WBV exercise while EMG activity was recorded from the gluteus maximus, rectus femoris, vastus medialis, vastus lateralis, biceps femoris, semitendinosus, tibialis anterior, peroneus longus, soleus, gastrocnemius medialis, and gastrocnemius lateralis. The additional loading conditions consisted of either no load or a weighted vest equivalent to 20% of body weight. Vibration frequencies of 0Hz, 10Hz, 20Hz, 30Hz, 40Hz, and 50Hz were applied. EMG root mean square (EMGrms) values were statistically analyzed using a 2 (Loading)×6 (Frequency) repeated-measures ANOVA.
RESULTS:
No significant interaction effects between loading and frequency were observed. The gluteus maximus exhibited significant main effects for both loading (p<0.001) and frequency (p<0.001), with higher EMGrms under additional loading. EMGrms values at 10Hz, 20Hz, and 30Hz were significantly higher than at 0Hz. In the quadriceps (rectus femoris, vastus medialis, vastus lateralis), only loading had a significant effect (p<0.001), with higher EMGrms in the additional loading condition. The hamstrings (semitendinosus, biceps femoris) showed significant effects of both loading (p<0.001) and frequency (semitendinosus: p=0.008; biceps femoris: p<0.001), with higher EMGrms in the additional loading condition. The semitendinosus showed significantly higher EMGrms at 10Hz than at 0Hz, while the biceps femoris exhibited significantly higher EMGrms at 10Hz and 20Hz than at 0Hz. The soleus demonstrated a significant loading effect (p<0.001), with higher EMGrms in the additional loading condition. The gastrocnemius lateralis showed a significant frequency effect (p=0.016), with EMGrms at 20Hz being significantly higher than at 50Hz. No significant effects of loading and frequency were observed in the gastrocnemius medialis, tibialis anterior, and peroneus longus.
CONCLUSION:
Additional loading and vibration frequencies in the range of 10–30Hz significantly enhanced lower limb muscle activation during WBV exercise. This study provides a more comprehensive understanding of how these factors influence neuromuscular responses by examining a wider range of lower limb muscles. These findings highlight the importance of optimizing loading and frequency parameters to maximize the efficacy of WBV in both training and rehabilitation settings.