Take A Walk -- and Live

By MICHAEL D. LEMONICK

Couch potatoes, your last excuse is gone. You knew you should be getting into your running shoes and hitting the pavement. After all, everyone concedes that exercising is one of the best ways to stave off heart attacks and other health problems. But hard physical exertion is downright unpleasant, and you -- along with about 50 million other sedentary Americans -- could be forgiven for putting it off or avoiding it altogether.

No more, though. A study published last week in the Journal of the American Medical Association says that even a minimal amount of exercise -- a brisk half-hour walk once a day is enough -- confers significant protection not only from cardiovascular disease and cancers but also against death from a wide range of other causes. Put plainly, people who exercise just a little bit tend to live longer.

The eight-year, 13,344-subject study, carried out by researchers at the Institute for Aerobics Research in Dallas, is hardly the first to establish a link between moderate exercise and longevity. But it is considered especially significant. For one thing, it includes both men and women, in contrast to earlier, mostly male surveys. For another, it strengthens the evidence that exercise can ward off cancer, a relationship discovered only in the past few years. And, perhaps most important, it is one of the largest studies ever done that relied on an objective measure of fitness, not just participants' descriptions of how much they exercise.

The researchers measured fitness in a straightforward way: they put people on a treadmill, set them walking, and periodically increased first the incline and then the speed of the treadmill until the walkers could no longer continue. The subjects were grouped into five different fitness levels based on their performance and followed for the next eight years.

At the end of that time, 283 of the participants, all of whom were in good health at the start of the study, had died. And after allowing for various other health-affecting factors, including smoking, age, cholesterol levels, weight, blood pressure and family history of heart disease, they found that deaths were sharply higher in the least-fit category than in the second-most- sedentary group -- more than double for men and almost twice as high for women.

In the most-fit groups, which included people in the habit of running up to 40 miles a week, death rates tended to be lower still, but the improvement was not so dramatic. In short, says Carl Caspersen, a physical-activity epidemiologist at the federal Centers for Disease Control in Atlanta: "You don't have to be a marathoner to greatly reduce your mortality. After that first jump in activity, you're not buying that much more reduced risk."

While this and earlier studies agree on the health benefits of regular, moderate exercise, no one is sure of the physiological mechanisms involved. It may be that exercise increases coronary blood flow, decreases clotting or both, which would limit the blood-vessel blockages that cause cardiovascular problems. And some scientists speculate that exercise increases bowel motility, a factor in avoiding colon cancer. Those questions may be answered in part by the next phase of the investigation, which is expected to include more than 40,000 people. Such speculations are literally academic, though. For the average man or woman, the message is clear: get moving.

CHART: NOT AVAILABLE

CREDIT: TIME Chart by Joe Lertola

CAPTION: FITNESS PAYS

With reporting by Andrew Purvis/New York