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.

Sleep quality in individuals with short-duration chronic spinal cord injury.

The aim of the study is to estimate the association between spinal cord injuries related medical factors and subjective sleep disturbance in individuals with short-duration chronic spinal cord injury. Seventy-nine individuals with traumatic spinal cord injuries were included in our study and evaluated using the Beck Depression Index for severity of depressive symptoms, Short-Form Health Survey for quality of life, Douleur Neuropathique 4 score for neuropathic pain severity, and the Pittsburgh Sleep Quality Index for subjective sleep disturbances in a tertiary rehabilitation center. Associated subjective sleep disturbance factors were predicted using multivariate binary logistic regression analysis. Subjective sleep disturbance frequency was 74.7 %, and significantly higher in individuals with paraplegia (P = 0.025, odds ratio, 9.74, 95% confidence interval, 1.21-78.14). Intermittent nighttime catheterization frequency and neuropathic pain severity levels were significantly higher in individuals with subjective sleep disturbance, and quality of life and depressive symptoms were significantly worse in individuals with subjective sleep disturbance. Poor-sleep quality was associated significantly with shorter spinal cord injury duration. The strongest associated factors for sleep disturbance were paraplegic involvement, severity of depressive symptoms (Beck Depression Index score), and quality of life (Short-Form Health Survey general health perceptions score) (odds ratio: 95% confidence interval, 29.75; 1.66-534.36, 1.47; 1.11-1.95, and 0.91; 0.85-0.97, respectively). Our study suggests that paraplegic involvement, low quality of life, and depressive mood are related to sleep disturbance in individuals with traumatic spinal cord injury.