A training regimen to adjust the body's motor reflexes may help improve mobility for some people with incomplete spinal cord injuries, according to a study supported by the National Institutes of Health.

The study involved 13 people who were still able to walk after incomplete spinal cord injuries that had occurred from 8 months to 50 years prior to the study. All had spasticity and an impaired ability to walk. The goal was to determine if these individuals could gain mobility by learning to suppress a spinal H-reflex, which is elicited by electrical stimulation rather than by a tendon stretch.

Participants in the study received electrical stimulation to the soleus of their weaker leg while standing with support. The first 2 weeks of the study involved baseline measurements of the resulting reflex. During the next 10 weeks, 9 participants underwent 3 training sessions per week, during which they viewed the size of their reflexes on a monitor and were encouraged to suppress it. A control group of 4 participants received the stimulation but no feedback about their reflexes. Before and after these sessions, the researchers measured the participants' walking speed over a distance of 10 meters and monitored their gait symmetry with electronic shoe implants.

Six of the 9 participants in the training group were able to suppress their reflexes. Their walking speed increased 59% on average, and their gait became more symmetrical. These improvements in speed and symmetry were not seen in 3 participants who were unable to suppress their reflexes, or in the control group. Many participants also spontaneously told the researchers they were noticing improvements in daily living activities. About 85% of these comments came from people who were able to control their reflexes after several weeks of training.

Study author Jonathan Wolpaw, MD, said he views reflex conditioning as a complement to current rehabilitation practices. The technique could be tailored to focus on specific reflexes that affect different muscle groups and, in some cases, to increase reflexes instead of decrease them. In its 2006 study, his group found that enhancing soleus H-reflex was beneficial for rats that had spinal cord injuries predominantly characterized by weakness without spasticity.

Aiko Thompson, PhD, who also authored the article, said she plans to study how durable the effects of training are, but such research presents a design challenge. "Once people noticed their mobility had improved, they started exercising more and getting involved with other types of therapy. Those activities are likely to have additional benefits and will be difficult to separate from the long-term effects of our reflex conditioning protocol," she said.