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Muscle Vibration

To date, many rehabilitative therapies have been proposed to help with muscle function and spasticity, such as, passive standing, muscle strengthening and electrical stimulation (Ji et al., 2016). Recently, interest has focused on muscle vibration, which aims to prevent/treat muscle atrophy and spasticity through the application of mechanical oscillations to skeletal muscles (Ji et al., 2016). The application of vibration to muscle-tendon complexes results in a stretch-shortening action, in turn, activating muscle spindles to trigger a reflexive muscle contraction (Menendez et al., 2016). Vibratory stimulus may be applied in a variety of ways including focal muscle vibration and whole body vibration. Focal muscle vibration applies low-amplitude and high frequency vibration stimulation to a specific muscle through a small portable device (Celletti et al., 2017), while whole body vibration involves standing, sitting or performing various tasks on a vibration platform (Liao et al., 2015; Park et al., 2018). The effects of muscle vibration therapy have been well documented in stroke patients and demonstrate an improvement in motor function, as well as balance, gait and mobility. However, the effects of muscle vibration therapy on functional outcomes in individuals with SCI are not well known.

The methodological details and results from one randomized controlled trial are presented in Table 15.

Table 15 Muscle Vibration Interventions post-SCI

Author Year

Country

Research Design

Score

Total Sample Size

MethodsOutcome
Gomes-Osman & Field-Fote 2015

USA

Crossover RCT

N=24

Population: Mean Age: 43.7 yr; Gender: males=21, females=3; Injury etiology: Motor Vehicle Accident=17, Diving=2, Non-traumatic=1, Unspecified=4; Severity of Injury: AIS C=9, AIS D=11, Unspecified=4; Level of Injury: C4=1, C5=4, C6=10, C7=5.

Intervention: Patients received three types of stimulation in a randomized order; transcranial direct current stimulation (tDCS), transcutaneous electrical nerve stimulation (TENS), and vibration therapy. Both TNS and vibration therapy was performed on the volar aspect of the wrist. tDCS was performed on the primary left/right motor area and on the contralateral supraorbital area. During each condition, the patients engaged in functional task practice. The intervention was provided once for each condition with a 1 wk break between each. Assessments were conducted at baseline, post-treatment and at 30 min post treatment.

Outcome Measures: Nine-hole Peg Test (9HPT), pinch strength, Corticomotor excitability/motor-evoked potentials, Visuomotor tracking task.

1.     Results on the 9HPT improved significantly from baseline to post treatment after patients received TENS (p=0.003) and tDCS (p=0.05) with improvements maintained from baseline to 30 min post treatment (p<0.001 and p=0.003 respectively).

2.     Vibration therapy did not significantly change from baseline to post treatment or 30 min post treatment.

3.     Pinch strength significantly improved from baseline to post treatment after vibration therapy only (p=0.03). At 30 min post treatment, patients demonstrated improved pinch strength after both vibration therapy (p=0.03) and tDCS (p=0.005) compared to baseline.

4.     Visuomotor tracking did not improve from baseline to post treatment for any of the conditions. Only tDCS improved from baseline to 30 min post treatment (p=0.05).

5.     Corticomotor excitability improved

significantly from baseline to post treatment after TENS (p=0.003) only but at 30 min post treatment, only vibration therapy demonstrated a significant improvement compared to baseline (p=0.006).

Effect Sizes: Forest plot of standardized mean differences (SMD±95%C.I.) as calculated from pre- and post-intervention data.

 

Backus et al. 2014

USA

Pre-Post

N=18

Population: Mean age: 40.5±13.0 yr; Gender: males=8, females=2; Level of injury: C2-C3=3, C4-C7=7; Mean ASIA motor score: 15.8±3.9; Mean time since injury: 3.0±1.1 yr.

Intervention: Test effect of assisted movement with enhanced sensation (AMES) using vibration to antagonist muscle to reduce impairments and restore upper limb function in people with incomplete tetraplegia. Two or three sessions over 9-13 wk per participant.

Outcome Measures: Strength and active motion tests on the AMES device, International Standards for the Neurological Classification of SCI (ISNCSCI) motor and sensory examinations, Modified Ashworth Scale (MAS), grasp and release test (GRT), Van Lieshout Test (VLT), Capabilities of Upper Extremity questionnaire (CUE).

1.     No significant change in MAS scores (p=0.371) or ISNCSCI scores (p=0.299 for motor, p=0.459 for sensory-light tough, p=0.343 for sensory-pin prick).

2.     Strength test scores increased significantly for MCP extension (p≤0.01) and flexion (p≤0.05) and for wrist extension (p≤0.001) and flexion (p≤0.01).

3.     Active motion test scores increased significantly for MCP joints (p≤0.001) and wrist (p≤0.001).

4.     Out of GRT, VLT and CUE scores, only GRT scores were significantly improved after training and slightly between post treatment and 3-mo post treatment (p=0.025).

 

Discussion

Currently, there is very little evidence to draw any conclusions about muscle vibration as a rehabilitative therapy in SCI. Given the evidence presented by Gomes-Osman & Field-Fote and Backus et al. (2014), vibration therapy is feasible in a SCI population. Pinch strength, muscle strength and grasp strength were temporarily improved with vibration therapy, however, no significant changes were observed with the nine-hole peg test or other measures of functional improvement. Based on the current evidence, muscle vibration therapy has little effect on functional outcomes in SCI patients. As such, future research is necessary in this area to determine the efficacy of muscle vibration therapy in SCI patients.

Conclusion

There is level 1a evidence (from one randomized controlled trial; Gomes-Osman & Field-Fote, 2015) that pinch strength significantly improves with vibration therapy but this does not translate to improvements in functional outcomes.

There is level 4 evidence (from one pre-post study; Backus et al., 2014) that an end effector utilizing muscle vibration can be safely used in patients with tetraplegia to significantly improve upper limb function.

More research is necessary to determine the efficacy of muscle vibration therapy in SCI rehabilitation.