Couch Potatoes, Arise!

There's nothing easier than falling out of shape, especially in the U.S. Americans may no longer lead the world in science, engineering and productivity, but with TiVo on the flat-screen, Domino's at the door and an arsenal of remotes within easy reach, we've got leisure time nailed.

Climbing off the couch and getting back into condition is a dicier proposition. Trying to do it too fast can actually be dangerous. "Among those at greatest risk for heart-attack death is the habitually sedentary person who engages in unaccustomed physical activity," warns Barry Franklin, physiologist and chairman of the American Heart Association's Physical Activities Committee. Before starting even a minimal exercise program, therefore, you should call your doctor for a preworkout O.K. or even a checkup.

Once you've been cleared for takeoff, the first step you take may be just that: a walking program that begins modestly and then builds up. Government guidelines recommend at least 30 minutes of moderate-intensity activities including walking most days of the week, but Franklin believes in starting even more slowly, if necessary. "I ask my patients if they could manage as little as eight to 10 minutes," he says. "Most of the time they say they can, and then come back having done 14 or 15."

Even that small start can yield big dividends. A good walking program may improve overall measures of physical health as much as 15% in just three months. Since the human body after age 25 experiences, on average, about a 1% falloff in fitness for every additional year of life, the numbers are easy to crunch. "That's a 15-year functional rejuvenation," Franklin says.

For folks aiming for more--weight loss, limberness, a competitive edge in sports--there are other avenues to becoming active again. Depending on how many years you've logged on the couch, high-impact activities such as jogging may not be for you--not if your creaky knees, ankles and hips have anything to say about it. Best to get yourself back in shape with a low-impact activity like swimming, cycling or rowing.

Whatever you choose, begin with a shorter workout than you believe you can handle. "Consciously underdo," advises exercise physiologist Carl Foster of the University of Wisconsin--La Crosse. "We're all 19 behind our eyes, but if you jogged 10 miles a day when you were in college, that doesn't mean you can do it now." Besides, once you're comfortable with a more modest workout load, you can slowly increase it--about 10% a week, Foster recommends. Government guidelines suggest that if you're having trouble finding the time or energy for a full exercise session, you can still get significant health benefits from 30 to 60 minutes of exercise broken up into 10- or 15-minute segments throughout the day.