ANN ARBOR, Mich. -- When someone's spinal cord is completely severed, brain signals can no longer reach the legs to tell the legs to walk.
A study in this month's journal Spinal Cord shows that those who have suffered a spinal cord injury can generate muscle activity independent of brain signals. Dan Ferris, now an assistant professor of kinesiology at U-M, led the research as part of his post-doctorate work with Susan Harkema at University of California Los Angeles David Geffen School of Medicine.
While many studies have shown that locomotor training, such as working with patients on treadmills, is a viable therapy for helping those who have suffered a spinal cord injury learn to walk again, Ferris and his UCLA colleagues added further evidence that adding weight to the limbs during therapy can provide an important sensory cue to help regain walking.
They also found that moving one leg in therapy can help activate muscles in the opposite leg.
"Nobody has been able to show that in humans before," said Ferris, also an assistant professor of biomedical engineering. "It appears there are left-to-right connections in the signal in the spinal cord, not just connections from the brain to the legs."
The research was partially supported by five grants from the National Institutes of Health.
The team worked with four patients with clinically complete spinal cord injury, doing about 30 sessions with each over about 1.5 years. They hooked each subject into a harness suspended over a treadmill. Trainers helped move the subjects' legs as they stepped on the treadmill.
When the subjects were positioned so that just one leg was on the moving treadmill belt and the other was off the side, not touching the treadmill surface, the team was able to get muscle response in one leg by simulating walking with the other.
"If you step one leg, you can get muscle activation in the other, even when it isn't moving," Ferris said. "This shows that it isn't just muscle stretch that causes activitation."
Ferris and the team---Harkema, Keith Gordan and Janell Beres-Jones---see great potential in this information for developing rehabilitation strategies.
Therapists helping patients recover from spinal cord injury should provide sensory information that simulates walking as closely as possible. Weight loading and movement in one leg can influence what happens in the other leg.
The Christopher Reeve Paralysis Foundation is funding another project, led by Ferris, to build powered braces to help those with spinal cord injury regain the ability to walk. Ferris speculates that perhaps such braces could help move the legs to recreate a more normal stepping pattern during rehabilitation. Ferris is testing a working model of the braces to assist patients in walking.
Harkema is heading up a second project funded by the foundation to study the therapeutic effects of stand training after spinal cord injury.
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