Treadmill exercise may help stroke survivors regain their ability to walk by rewiring parts of the brain responsible for controlling balance and motor skills to compensate for stroke damage, researchers report in an American Heart Association rapid access journal report.

In a randomized, controlled study, patients with long term disability after stroke who did six months of treadmill exercise training increased blood oxygenation and flow in the brainstem and cerebellum by 72 percent on imaging tests. Brain activity changes did not occur in patients who did stretching exercise. The treadmill group also increased their walking velocity and their fitness more than those in the stretching group.

"Revealing a mechanism by which treadmill therapy improves a stroke survivor's gait was the novel goal of the study," said Andreas Luft, M.D., one of the study's lead authors and a professor of clinical neurology and neurorehabilitation in the Department of Neurology at the University of Zurich in Switzerland. "This study provides the first evidence of increased activation in cortical and subcortical circuitry produced by treadmill exercise training in stroke survivors."

In the study conducted at the University of Maryland and Baltimore Veterans Affairs Medical Center, researchers compared 37 patients who performed "progressive task repetitive treadmill therapy" to 34 patients who did stretching to determine which could improve walking among stroke survivors with chronic partial paralysis on one side of the body. They found:

• The stroke survivors who used the treadmill for six months benefited significantly more than those who used stretching for a comparable period.

• The treadmill group increased its peak treadmill walking velocity by 51 percent compared to the stretching group's 11 percent, and it increased its average over-ground walking velocity during six minutes by 19 percent compared to the stretching group's 8 percent.

• Cardiorespiratory fitness in the treadmill group increased 18 percent but decreased 3 percent in the stretching group.

Researchers compared functional magnetic resonance images (fMRI) of participants' brains while participants did knee-flexing exercises that mimic walking. The fMRIs showed increased blood oxygenation and flow in the brainstem and cerebellum of the stroke survivors who had used the treadmill but not in those who did stretching.

Researchers said the increases in blood oxygenation and flow indicated that the cerebellum and brainstem had been "recruited" to replace some of the walking functions of the cortical brain that had been damaged by the strokes.

"We saw what we call an equivalent of neuroplasticity - a change in brain activation that reflects the brain's adaptability," said Luft.

The subcortical networks could be where the brain rewires its circuitry and may explain why treadmill exercise improves walking in partially paralyzed stroke survivors even a decade after the stroke, he said.

"It is promising that treadmill exercise can stimulate new or underused brain circuits and improve walking in stroke survivors even after completion of conventional rehabilitation therapy."

• Among the implications of the study:

• Improved function can occur long after stroke.

• The standard therapy option of stretching is insufficient to improve the gait of long-term stroke survivors.

• Treadmill exercise should be included in long-term rehabilitation programs for stroke.

Treadmill therapy should be appreciated for its ability to restore survivors' aerobic fitness and to counter the immobility that can lead to cardiovascular disease and diabetes.

"It becomes more clear that the aerobic treadmill therapy has to be included in the therapy programs that are offered to chronic stroke survivors," said Luft, who is also an adjunct assistant professor in the neurology departments at the University of Maryland and Johns Hopkins University in Baltimore and a visiting researcher at the Baltimore Veterans Affairs Medical Center where researchers conducted the study.

Previous studies by co-lead author Richard F. Macko, M.D., show that this program also improves glucose metabolism, potentially preventing the development of diabetes in stroke patients.

Other co-authors are: Larry W. Forrester, Ph.D.; Federico Villagra, Ph.D.; Fred Ivey, M.D.; John D. Sorkin, M.D., Ph.D.; Jill Whitall, Ph.D.; Sandy McCombe-Waller, PT, Ph.D.; Leslie Katzel, M.D., Ph.D.; Andrew P. Goldberg, M.D.; and Daniel F. Hanley, M.D.
Funding was provided by the U.S. National Institutes of Aging Health, Claude D. Pepper Older American Independence Center, the University of Maryland, the U.S. Department of Veterans Affairs, the France-Merrick Foundation, the Johns Hopkins University, the Eleanor Naylor Dana Charitable Trust and a German research foundation.