[Purpose] The beneficial neuromuscular effects of whole-body vibration are explained by the tonic vibration or bone myoregulation reflex. Depending on factors that remain undefined, whole-body vibration may activate the tonic vibration or bone myoregulation reflex. We aimed to examine whether voluntary contraction facilitates activation of the tonic vibration reflex during whole-body vibration. [Participants and Methods] Eleven volunteers were included in this study. Local and whole-body vibrations were applied in a quiet standing (without voluntary contraction) and a semi-squatting (isometric soleus contraction) position. Local vibration was applied to the Achilles tendon. Surface electromyography was obtained from the soleus muscle. The cumulative average method was used to determine soleus reflex latency. [Results] In the quiet standing position, the bone myoregulation reflex latency was 39.9 ± 4.1 milliseconds and the tonic vibration reflex latency was 35.4 ± 3.6 milliseconds. Whole-body vibration application in the semi-squatting position activated the tonic vibration reflex in four participants and the bone myoregulation reflex in seven participants. Local vibration activated the tonic vibration reflex in both positions for all participants. [Conclusion] Simultaneous whole-body vibration application and voluntary contraction may activate the tonic vibration reflex. Determining the spinal mechanisms underlying the whole-body vibration exercises will enable their effective and efficient use in rehabilitation and sports.
Keywords: Muscle strength; Tonic vibration reflex; Whole-body vibration.
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