Plastic changes induced by muscle focal vibration: A possible mechanism for long-term motor improvements

Effects of prolonged vibration to the flexor carpi radialis muscle on intracortical excitability

Prolonged local vibration (LV) can induce neurophysiological adaptations thought to be related to long-term potentiation or depression. Yet, how changes in intracortical excitability may be involved remains to be further investigated as previous studies reported equivocal results. We therefore investigated the effects of 30 min of LV applied to the right flexor carpi radialis muscle (FCR) on both short-interval intracortical inhibition (SICI) and intracortical facilitation (ICF). SICI and ICF were measured through transcranial magnetic stimulation before and immediately after 30 min of FCR LV (vibration condition) or 30 min of rest (control condition). Measurements were performed during a low-intensity contraction (n = 17) or at rest (n = 7). No significant SICI nor ICF modulations were observed, whether measured during isometric contractions or at rest (p = 0.2). Yet, we observed an increase in inter-individual variability for post measurements after LV. In conclusion, while intracortical excitability was not significantly modulated after LV, increased inter-variability observed after LV may suggest the possibility of divergent responses to prolonged LV exposure.

Sensory Stimulation of the Triceps Surae Muscle Complex Modulates Spinal Reflex Responses-A Comparison between Tapotement Massage and Repetitive Peripheral Magnetic Stimulation (rPMS)

BACKGROUND

The reduction of muscular hypertonia is important in the treatment of various diseases or rehabilitation. This study aims to test the efficacy of a 5 Hz mechanical muscle stimulation (tapotement massage) in comparison to a 5 Hz repetitive peripheral magnetic stimulation (rPMS) on the neuromuscular reflex response.

METHODS

In a randomized control trial, 15 healthy volunteers were administered with either 5 Hz rPMS, tapotement massage, or rPMS sham stimulation. The posterior tibial nerve was stimulated with rPMS and sham stimulation. The Achilles tendon was exposed to a mechanically applied high-amplitude 5 Hz repetitive tendon tapotement massage (rTTM). The tendon reflex (TR) was measured for the spinal response of the soleus muscle.

RESULTS

After rPMS, there was a reduction of the TR response (-9.8%, p ≤ 0.034) with no significant changes after sham stimulation. Likewise, TR decreased significantly (-17.4%, p ≤ 0.002) after Achilles tendon tapotement intervention.

CONCLUSIONS

These findings support the hypothesis that both afferent 5 Hz sensory stimulations contributed to a modulation within the spinal and/or supraspinal circuits, which resulted in a reduction of the spinal reflex excitability. The effects could be beneficial for patients with muscle hypertonia and could improve the functional results of rehabilitation programs.

Immediate effects of local muscle vibration on static and dynamic balance control in individuals with chronic ankle instability

OBJECTIVES

To investigate the immediate effects of local muscle vibration (LMV) on static and dynamic balance control in individuals with and without chronic ankle instability (CAI).

DESIGN

Quasi-experimental study.

SETTING

Research laboratory.

PARTICIPANTS

Twenty-six individuals with CAI and 26 healthy controls.

MAIN OUTCOME MEASURES

Center of pressure variables (mean total velocity and displacement in anteroposterior (AP) and mediolateral (ML) directions) during single-leg standing with eyes open and eyes closed and also reach distances in anterior (ANT), posteromedial (PM), and posterolateral (PL) directions of the modified star excursion balance test (MSEBT) were assessed before and after LMV.

RESULTS

Statistical analyses showed a significant decrease in mean total velocity and displacement in AP direction from before to after LMV in eyes open condition for both individuals with CAI (p = 0.025, p = 0.041, respectively) and healthy controls (p = 0.001, p = 0.003, respectively). Similar results were observed in eyes closed condition for both individuals with CAI (p < 0.001, p < 0.001, respectively) and healthy controls (p = 0.040, p = 0.014, respectively). The results also showed increased reach distances in ANT (p < 0.001), PM (p < 0.001), and PL directions (p < 0.001) in all participants after LMV.

CONCLUSION

Our results suggest that LMV may be a useful tool in rehabilitation of static and dynamic balance deficits in individuals with CAI.

Effectiveness of Focal Muscle Vibration in the Recovery of Neuromotor Hypofunction: A Systematic Review

Adequate physical recovery after trauma, injury, disease, a long period of hypomobility, or simply ageing is a difficult goal because rehabilitation protocols are long-lasting and often cannot ensure complete motor recovery. Therefore, the optimisation of rehabilitation procedures is an important target to be achieved. The possibility of restoring motor functions by acting on proprioceptive signals by unspecific repetitive muscle vibration, focally applied on single muscles (RFV), instead of only training muscle function, is a new perspective, as suggested by the effects on the motor performance evidenced by healthy persons. The focal muscle vibration consists of micro-stretching-shortening sequences applied to individual muscles. By repeating such stimulation, an immediate and persistent increase in motility can be attained. This review aims to show whether this proprioceptive stimulation is useful for optimising the rehabilitative process in the presence of poor motor function. Papers reporting RFV effects have evidenced that the motor deficits can be counteracted by focal vibration leading to an early and quick complete recovery. The RFV efficacy has been observed in various clinical conditions. The motor improvements were immediate and obtained without loading the joints. The review suggests that these protocols can be considered a powerful new advantage to enhance traditional rehabilitation and achieve a more complete motor recovery.