PAD, a condition that affects eight to 10 million adults, and 5 percent of people ages 50 and up, is a form of atherosclerosis that affects the blood vessels of the legs. The buildup of cholesterol-laden plaque, similar to that which occurs in the arteries of the heart, reduces blood flow to the legs over time. The limited blood flow can't meet extra demand from the legs during walking or other exercise, resulting in pain, aching and fatigue.
"Unlike coronary artery disease patients, who should stop exercising as soon as they experience chest pain, PAD patients with cramping pain, called claudication, should walk until they reach a moderate level of leg pain and then continue for several minutes," says Kerry J. Stewart, Ed.D., Hopkins' director of clinical exercise physiology and lead author of the study. "After a few minutes of rest, the walking should be resumed, and this cycle should be repeated until the person can walk for 50 minutes. A supervised exercise program in which patients walk on a treadmill several times a week may be the best way to eventually ease the pain."
Stewart and colleagues at the Universities of Colorado and Minnesota reviewed more than 120 studies to reach their conclusions about exercise and PAD. Because patients with claudication experience pain when they exercise, they often slack off, Stewart says.
"As a result, many are so unfit they become housebound or dependent on others," he says. "In a gym setting such as a cardiac rehabilitation program, with staff monitoring and encouraging them, they're more likely to keep it up. The rewards are obvious: Studies show that patients who exercise three or more times a week for at least three months have substantial increases in the distance they can walk without painful symptoms."
Adds Alan T. Hirsch, M.D., of the University of Minnesota, senior author of the study, "Supervised exercise is exceedingly safe and effective for many patients, so it is a shame that, because of insurance reimbursement issues, such cardiac rehabilitation programs remain almost universally unavailable to Americans with PAD and claudication."
Although exercise training does not appear to increase the amount of blood that reaches the limbs, it increases muscle metabolism and endothelial function, which regulates blood vessels' ability to expand and contract. There also appear to be improvements in blood flow, allowing more blood to reach muscle cells, and a reduction in systemic inflammation. Another benefit is a more efficient walking style in patients who often alter the mechanics of walking to avoid pain.
Exercise also improves overall cardiovascular health – lowering blood pressure, improving cholesterol levels, lowering blood glucose levels in diabetics and reducing obesity, Stewart says. He cautions that PAD patients see their doctor for medical clearance before starting a walking program.
Exercise training is the cornerstone of treatment for most PAD patients, along with dietary and drug therapies for smoking cessation, lowering blood pressure and cholesterol, controlling diabetes, and preventing blood clots. For patients with worsening PAD, or for those who cannot or will not exercise, surgical treatments such as leg artery bypass or leg angioplasty may be helpful.
Study co-authors were William R. Hiatt, M.D., and Judith G. Regensteiner, Ph.D., of the University of Colorado Health Sciences Center in Denver.
Stewart, Kerry J., et al, "Exercise Training for Claudication: Mechanisms of Improvement," The New England Journal of Medicine, Dec. 12, 2002, Vol. 347, No. 24, pages 1941-1951.
Related Web sites:
Johns Hopkins Division of Cardiology
http://www.cardiology.hopkinsmedicine.org
Vascular Disease Foundation
http://www.vdf.org
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New England Journal of Medicine