Neuromuscular activity during whole-body vibration of different amplitudes and footwear conditions: implications for prescription of vibratory stimulation

Abstract

This study investigated the magnitude of whole-body vibration (WBV) at 30 Hz induced in surface electromyography root-mean-square (EMGrms) signals of different amplitudes and footwear conditions of unloaded isometric half squat (100). For this purpose, 10 healthy and active males (age 28.7 +/- 4.6 yr; height 180 +/- 5.9 cm; and weight 90 +/- 13.4 kg) volunteered to participate in this study. Subjects were exposed to the WBV treatment using a vibration platform (FreeMotion Fitness iTonic). The subjects were exposed randomly to 4 different treatments of WBV: with shoes 2 mm amplitude, without shoes 2 mm, with shoes 4 mm, and without shoes 4 mm. The EMGrms signals were recorded from the vastus lateralis and the gastrocnemius medialis muscle during the different conditions. The WBV treatments resulted in a significantly higher (p <or= 0.05) EMGrms compared with unloaded isometric half squat (without WBV). The WBV treatment that induced the highest EMGrms signals of the vastus lateralis was during the amplitude of 4 mm without shoes (+62.7%; p < 0.01), whereas 4 mm with shoes induced the highest EMGrms signals of the gastrocnemius medialis (+142.7%; p < 0.01). These data suggest that wearing shoes does alter the neuromuscular response to WBV stimuli, and exercise professionals should consider such differences when using WBV to target neuromuscular activation of such muscle groups. In this study, the magnitude of the WBV effect was clearly higher with the amplitude 4 mm versus 2 mm for the vastus lateralis muscle and gastrocnemius medialis muscle. The vastus lateralis showed the greatest activity without shoes and at amplitude of 4 mm. The maximal activation for the gastrocnemius medialis was measured with shoes at 4 mm.