page 3 -While you wait: the cost of inactivity

While you wait: the cost of inactivity
Nutrition Action Healthletter, Dec, 2005 by Bonnie Liebman

Why? In stimulated mice, an enzyme that degrades amyloid deposits is more active. (7) "So there may be a specific anti-Alzheimer's effect of physical activity and social stimulation," he explains.

4 The Heart

Every year, 1.2 million Americans have a heart attack. It's no surprise that couch potatoes have a higher risk.

"Exercise affects the function of the heart muscle, but it also affects the blood vessels, from the large aortic artery to the veins and the small capillaries," says Tufts University's Miriam Nelson.

Researchers have long known that regular exercise can boost HDL ("good") cholesterol, which is the cholesterol that's on its way out of the arteries. But in recent years, they've learned that physical activity also makes the lining of blood vessels--the endothelium--more flexible.

"If partially blocked arteries are more elastic, they can relax better and send more blood to the heart muscles," explains Harvard's I-Min Lee. "It's like pumping blood through a rubber hose instead of a concrete pipe."

And you don't have to be an athlete to protect your heart.

In a study that tracked nearly 40,000 women for five years, those who walked briskly for at least an hour a week were half as likely to be diagnosed with heart disease as those who did no regular walking. (8) The risk was even lower for women who jogged or did other vigorous activity.

Scientists have good reason to believe that regular exercise protects the heart. "We know that physical activity has beneficial effects on risk factors for heart disease like lipids, blood pressure, and insulin sensitivity," explains Lee.

What's more, researchers have tested the impact of exercise training on people who already have heart disease.

"If they are assigned to an exercise program, they have a lower risk of dying and of dying from heart disease," says Lee.

5 Stroke

People who are active are 25 percent less likely to have a stroke than their sedentary counterparts.

(9) How can exercise keep strokes at bay?

"By lowering blood pressure, raising HDL cholesterol, and reducing the risk of blood clots," says Lee.

In the U.S., most strokes occur when a blood clot gets stuck in a partially clogged artery that feeds the brain. "Physical activity has the same effect on arteries to the brain as on arteries to the heart," she adds.

The evidence is less solid that regular exercise wards off less-common hemorrhagic strokes, which occur when a blood vessel in the brain bursts. However, if exercise prevents hemorrhagic stroke, says Lee, "it's probably by lowering blood pressure."

High blood pressure, or hypertension, is the biggest risk factor for any stroke. And researchers are now finding that a regular spin on the bike or walk on the treadmill doesn't lower blood pressure in everyone.

"It's a mixed bag," says the University of Maryland's Ben Hurley. "Regular aerobic exercise reduces blood pressure in aboperformers in 75 percent of people."

In others, blood pressure doesn't budge. (10) "Our group found that blood pressure improved in people with one gene profile, but not in others."