Whole body vibration activates the tonic vibration reflex during voluntary contraction.

[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.

High-frequency whole-body vibration activates tonic vibration reflex.

Objectives: The aim of this research was to examine whether high-frequency whole-body vibration activates the tonic vibration reflex (TVR). Patients and methods: The experimental study was conducted with seven volunteers (mean age: 30.8±3.3 years; range, 26 to 35 years) between December 2021 and January 2022. To elicit soleus TVR, high-frequency (100-150 Hz) vibration was applied to the Achilles tendon. High-frequency (100-150 Hz) whole-body vibration and low-frequency (30-40 Hz) whole-body vibration were applied in quiet standing. Whole-body vibration-induced reflexes were recorded from the soleus muscle using surface electromyography. The cumulative average method was used to determine the reflex latencies. Results: Soleus TVR latency was 35.6±5.9 msec, the latency of the reflex activated by high-frequency whole-body vibration was 34.8±6.2 msec, and the latency of the reflex activated by low-frequency whole-body vibration was 42.8±3.4 msec (F(2, 12)=40.07, p=0.0001, ƞ2 =0.87). The low-frequency whole-body vibration-induced reflex latency was significantly longer than high-frequency whole-body vibration-induced reflex latency and TVR latency (p=0.002 and p=0.001, respectively). High-frequency whole-body vibration-induced reflex latency and TVR latency were found to be similar (p=0.526). Conclusion: This study showed that high-frequency whole-body vibration activates TVR.

The reflex mechanism underlying the neuromuscular effects of whole-body vibration: Is it the tonic vibration reflex?

OBJECTIVES: Whole-body vibration (WBV) is applied to the sole of the foot, whereas local mechanical vibration (LMV) is applied directly to the muscle or tendon. The time required for the mechanical stimulus to reach the muscle belly is longer for WBV. Therefore, the WBV-induced muscular reflex (WBV-IMR) latency may be longer than the tonic vibration reflex (TVR) latency. The aim of this study was to determine whether the difference between WBV-IMR and TVR latencies is due to the distance between the vibration application point and the target muscle. METHODS: Eight volunteers participated in this study. The soleus reflex response was recorded during WBV, LMVs, and tendon tap. LMVs were applied to the Achilles tendon and sole of the foot. The latencies were calculated using the cumulative averaging technique. RESULTS: The latency (33.4±2.8 ms) of the soleus reflex induced by the local foot vibration was similar to the soleus TVR latency (30.9±3.2 ms) and T-reflex (32.0±2.4 ms) but significantly shorter than the latency of the soleus WBV-IMR (42.3±3.4 ms) (F(3,21)=27.46, p=0.0001, partial η2=0.797). CONCLUSIONS: The present study points out that the neuronal circuitries of TVR and WBV-IMR are different.