Effect of 4-min vertical whole body vibration on muscle performance and body balance: a randomized cross-over study.

The purpose of this randomized cross-over study was to investigate the effects of a 4-min long, 2-mm vertically-vibrating vibration-exercise on muscle performance and body balance in healthy subjects. Sixteen volunteers (eight men and women aged 18-35 years) underwent both the 4-min vibration- and sham-interventions in a randomized order on different days. Performance- and balance-tests (stability platform, grip strength, extension strength of lower extremities, tandem-walk, vertical jump and shuttle-run) were done 10 minutes before (baseline) and 2 and 60 minutes after the intervention. In addition, the effect of vibration on the surface electromyography (EMG) of soleus, vastus lateralis, gluteus medius, and paravertebralis muscles was investigated during the vibration. The 4-min vibration-loading did not induce any statistically significant change in the performance- or balance-tests at the 2- or 60-min tests. Interestingly, however, the mean power frequency of the EMG in the vastus lateralis and gluteus medius muscles decreased during the vibration-intervention, indicating muscle fatigue, particularly in the hip region. It was concluded that a 4-min long, 2-mm vertically-vibrating vibration-stimulus did not induce changes in the performance and balance tests. Future studies should focus on evaluating the effects of different kinds of vibration-regimens, as well as the long-term effects of vibration-training, on body balance and muscle performance, and, as a broader objective, on bone.