Vibration elicits involuntary, step-like behavior in individuals with spinal cord injury.

BACKGROUND: Impaired walking is a debilitating consequence of spinal cord injury (SCI). This impairment arises, to some degree, from disruption of supraspinal pathways that activate the spinal locomotor central pattern generator (CPG). Evidence in nondisabled (ND) individuals suggests that vibration activates locomotor CPGs, eliciting involuntary step-like behavior. OBJECTIVE: To compare vibration-elicited step-like behavior in individuals with chronic SCIs with the responses of ND individuals and to assess the influence of locomotor training on these responses. METHODS: Participants included 7 individuals with motor-incomplete SCIs (MISCIs) and 6 with motor-complete SCIs (MCSCIs) who were untrained, 6 individuals with MISCIs who underwent locomotor training, and 8 ND individuals. Kinematic and EMG data were collected while vibration was applied to the quadriceps, hamstrings, or tensor fascia latae (TFL) muscles. Consistency and robustness of vibration-elicited responses was determined from hip and knee angle data. RESULTS: Consistent and reliable step-like behaviors were elicited in individuals with MISCIs and MCSCIs, although responses were not as robust as those in ND individuals. Vibration to the TFL elicited the most robust responses. Consistency and robustness were not influenced by SCI severity or locomotor training but appeared to increase with repeated testing. CONCLUSION: These results confirm that vibration elicits step-like behaviors in individuals with SCIs, even those with no voluntary motor function in the legs. Further research is warranted to investigate the use of vibration as an approach to activating the spinal CPGs associated with stepping, perhaps as an adjunct to locomotor training for individuals with SCIs.

Whole-body vibration improves walking function in individuals with spinal cord injury: a pilot study.

Injury to the central nervous system often results in impairments that negatively affect walking function. Prior evidence suggests that vibration may improve walking function. The purpose of this study was to determine whether repeated use of whole-body vibration (WBV) is associated with improvements in walking function in individuals with spinal cord injury (SCI). Subjects were 17 individuals with chronic (> or = 1 year), motor-incomplete SCI. Subjects were tested before and after participation in a 12-session (3 days/week for 4 weeks) intervention of WBV. We assessed change in walking function via 3D motion capture, with walking speed as the primary outcome measure. We also assessed the influence of the WBV intervention on secondary gait characteristics, including cadence, step length, and hip-knee intralimb coordination. Walking speed increased by a mean of 0.062+/-0.011 m/s, a change that was statistically significant (p<0.001). The WBV intervention was also associated with statistically significant increases in cadence, and both the stronger and weaker legs exhibited increased step length and improved consistency of intralimb coordination. Changes in cadence and step length of the stronger leg were strongly correlated with improvements in walking speed. The improvement in walking speed observed with the WBV intervention was comparable to that reported in the literature in association with locomotor training. This magnitude of change has been identified as being clinically meaningful, even in non-clinical populations. These findings suggest WBV may be useful to improve walking function with effects that may persist for some time following the intervention.

Effect of whole-body vibration on quadriceps spasticity in individuals with spastic hypertonia due to spinal cord injury.

PURPOSE: Individuals with spinal cord injury (SCI) often have involuntary, reflex-evoked muscle activity resulting in spasticity. Vibration may modulate reflex activity thereby decreasing spasticity. This study suggests feasibility of using whole-body vibration (WBV) to decrease quadriceps spasticity in individuals with SCI. METHODS: Participants were individuals (n=16) with spastic quadriceps hypertonia due to chronic SCI (> 1 year). Quadriceps spasticity was measured by gravity-provoked stretch (Pendulum Test) before (initial) and after (final) a 3 day/week, 12-session WBV intervention. In addition, differences between immediate (immediate post-WBV) and delayed (delayed post-WBV) within-session effects were quantified. Finally, we assessed response differences between subjects who did and those who did not use antispastic agents. RESULTS: There was a significant reduction in quadriceps spasticity after participation in a WBV intervention that persisted for at least eight days. Within a WBV session, spasticity was reduced in the delayed post-WBV test compared to the immediate post-WBV test. The WBV intervention was associated with similar changes in quadriceps spasticity in subjects who did and those who did not use antispastic agents. CONCLUSIONS: Vibration may be a useful adjunct to training in those with spasticity. Future studies should directly compare the antispastic effects of vibration to those of antispastic agents.