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A training program of moderate aerobic exercise can increase motor and sensory function years after a stroke and improve the abnormal glucose metabolism that raises the risk of a repeat stroke, according to research presented at the Diabetes Translation Conference held by the Centers for Disease Control and Prevention (CDC) April 30–May 3 in Atlanta.
"With the right kind of exercise program, you can improve function and insulin sensitivity years after a stroke," says Richard F. Macko, MD, director of the Center of Excellence in Exercise and Robotics for Neurological Disorders at Baltimore Veterans Affairs (VA) Medical Center, one of the VA's Rehabilitation Research and Development Centers of Excellence.
Under usual circumstances, paretic muscle from the side of the body paralyzed by stroke undergoes changes that affect glucose metabolism, according to Macko. The muscle quickly becomes atrophied, infiltrated with fat, and predominated by "fast twitch" fibers that are less sensitive to insulin than normal muscle.
Measures of fitness in stroke patients tend to deteriorate quickly. "Stroke patients are half as fit as able-bodied but inactive individuals," Macko says.
GLUCOSE AND STROKE CONNECTION
Diabetes and stroke are closely linked. A person with diabetes is twice as likely to have a stroke than somebody with normal blood glucose metabolism. Ongoing hyperglycemia is likely to contribute to repeated strokes, as about a third of all stroke patients have another stroke within 5 years, according to Macko.
In 2004, Macko and colleagues conducted a study to determine the prevalence of abnormal glucose metabolism among patients with stroke who were screened for exercise rehabilitation at Baltimore VA Medical Center.1
A total of 216 chronic hemiparetic stroke patients were recruited through
local outpatient clinics or by a media campaign. All had completed
conventional inpatient and outpatient therapy, and all were an average 
3
years post-stroke.
Of the 216, 145, or 77%, had abnormal glucose metabolism. Seventy-five participants were identified as diabetic, based on medical history, and another 70 were found to have diabetes or impaired glucose tolerance on a fasting plasma glucose test.
CHALLENGING CONVENTIONAL WISDOM
Conventional rehabilitation after a stroke concentrates on moving patients toward independence by recovering activities of daily living like mobility, eating, dressing, and grooming. The duration of physical therapy is typically about 6 weeks, starting immediately after stroke, according to Macko.
"People believed that there was a plateau of recovery" that tops out around 11 or 12 weeks after a stroke, Macko says. But with the new study results from a repetitive, task-oriented aerobic exercise program, "the notion of a short window of recovery after stroke is gone," he says. Macko and colleagues have shown that a program focusing on, repetitive, task-oriented aerobic exercise can improve physical functioning and produce significant healthful changes in glucose metabolism—years after a stroke.
The program's lower-limb workouts include using a treadmill modified with handrails and other safety devices, as well as stair-stepping, shifting weight from foot to foot, and other exercises tailored to the patient's abilities. The upperextremity exercises include reaching, grasping, and other repetitive movements.
At the CDC diabetes meeting, Macko presented the findings of a pilot study of 20 patients who had strokes an average of 5 years before enrollment. The findings of the study, submitted for publication, show that a regimen of two 1-hour exercise sessions per week produces improvements within 2 months.
After 2 months of therapy, participants showed significant improvements in peak VO2—a measure of overall oxygen consumption that indicates fitness capacity—as well as improved insulin response and glucose control. The exercise participants had a 30% improvement in the distance walked in 6 minutes, and an increase in VO2 peak from 3% in the control group to 17% in the exercise group. Blood tests showed that after exercise training, insulin response was reduced by 25%. Almost 60% of those who had exercise training showed improved results from the oral glucose tolerance test, compared with 9% in the control group.
"Seven of 12 patients who were diabetic or pre-diabetic were reclassified" after participating in the program, Macko says. "This is remarkable. You don't usually see improvements like this."
Meanwhile, post-stroke subjects in the control group who did not participate in the exercise rehabilitation program continued to show decline on markers of physical functioning and metabolic risks.
TRANSLATING A PILOT INTO PRACTICE
Based on the promising preliminary results, the post-stroke exercise program is being rolled out in a collaborative effort with researchers in the Tuscany region of Italy. About 200 patients are enrolled in community-based clinics there.
"We're taking the principles of the training program and adapting them to a community setting," Macko says.
Ideally, he notes, such an aerobic exercise program should be adopted in the U.S., where the aging baby boom population is expected to cause a doubling in the number of strokes by 2040.
"Our current health care system is not set up with exercise programs that address the long-term, chronic disability of stroke," says Macko. "It's a huge problem."
Programs of aerobic exercise rehabilitation not only could help people with stroke regain mobility and physical functioning, but also could reduce the cardiometabolic risks that make them vulnerable to more strokes.
"We know these interventions work, and we know how they work,"
Macko says. "We need to get them out of the university hospital and into
the community." 
Footnotes
Learn more about the research program conducted by Richard F. Macko, MD, on moderate aerobic exercise for post-stroke rehab at www.grecc.umaryland.edu/pages/faculty/macko_richard.shtml.
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