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
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.
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.
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.
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