High-frequency whole-body vibration activates tonic vibration reflex

Abstract

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.

Keywords: Latency; muscle spindle; muscle strength; vibration..

Figure 1. Experimental vibration setup. (a) Low-frequency WBV, (b) high-frequency WBV applied to the heel, and (c) Achilles tendon vibration. An Acc was fixed on a vibration plate and mounted on the Achilles tendon. To record reflex response, a pair of surface EMG electrodes was placed on the soleus muscle. WBV: Whole-body vibration; Acc: Accelerometer.

Figure 2. Determination of reflex latency using the cumulative averaging method. (a) Three averaged Acc curves, each representing different vibration frequencies. (b) Standard error curve of three averaged acceleration sinusoidal curve. (c) Three averaged rectified EMG traces, each representing different vibration frequencies. (d) Standard error curve of three averaged rectified EMG traces. The empty circle and Line-1 (L1) represent the peak of spikes in the rectified EMG data as the trigger point. Line-2 (L2) represents the lowest value on the SE curve for the EMG data, indicating the onset point of the reflex response to the vibration stimulus. Line-3 (L3) represents the lowest value on the SE curve for the acceleration data, indicating the effective stimulus time point. Acc: Acceleration; SE: Standard error; EMG: Electromyography; SEMG: Surface electromyography.

Figure 3. The latency of low-frequency WBV-IMR, high-frequency WBV-IMR, TVR, and tendon reflex for soleus muscle (error bar with a 95% confidence interval). ms: Millisecond; T-reflex: Tendon reflex; TVR: Tonic vibration reflex; WBV-IMR: Whole-body vibration-induced muscular reflex.