Short bursts of exercise better than nothing

Couch potatoes, start your engines.

For those who can't seem to get the recommended 60 to 90 minutes of daily physical activity, new guidelines from the American College of Sports Medicine and the American Heart Association have just set the bar a little lower.

How low?

The guidelines recommend 30 minutes of brisk walking -- or other similar moderately intensive physical activity -- five times a week for adults. If you're willing to do a higher-intensity workout -- jogging, for example -- you can get by with 20 minutes three times a week. Those amounts are enough to reap major health benefits, according to the guidelines, which also advise that adults lift weights at least twice a week.

If that advice sounds familiar, you're right. It's almost identical to guidelines issued in 1995 by the college and the federal Centers for Disease Control and Prevention.

Confused? You're not alone. Exercise researchers have debated the subject for more than a decade.

You might find yourself asking some questions about the latest guidelines:

• Wow! I might be able to fit in those 30 minutes of exercise, but what happened to the 60 to 90 minutes of activity? That's still the level of exercise recommended by both the 2005 U.S. Dietary Guidelines and the Institute of Medicine, but it was set to help people control their body weight.

There's good evidence from the National Weight Control Registry -- a group of several thousand "successful losers" -- that at least an hour a day of activity is needed for weight loss and weight maintenance. But for other health benefits, 30 minutes of moderate activity five days a week -- or 20 minutes of vigorous exercise three times a week -- seems to do the trick, says Steven Blair, a professor of exercise science at the University of South Carolina and co-chair of the committee that drafted the latest guidelines.

• What exactly are those benefits? "There's a long laundry list of health benefits," says Glenn Gaesser, an exercise physiologist at the University of Virginia, who underscores that improvements occur "even if body weight does not change."

Among the improvements are lower blood pressure, better control of blood sugar and less insulin resistance -- a condition that often precedes Type 2 diabetes. Also, blood fat levels, which hike heart disease risk, are reduced. There's also less inflammation, which appears to help cut heart disease risk and may improve arthritis.

• Do I have to do those 30 minutes at one time? No. You can break them down into 10-minute increments. The guidelines say that doing three bouts of exercise a day produces the same benefits as getting 30 minutes of moderate activity at once.

• Are there other options? Yes, the latest guidelines encourage mixing and matching activities to fit your schedule. So you might walk for 30 minutes twice a week and then jog for 20 minutes a couple of times. Or you could play tennis, swim, ride a bike, shoot some hoops, play Frisbee or go square dancing. You get the idea.

• Once I've gotten in my 30 minutes, am I done? Technically, yes. But the more active you are, the better. Consider 30 minutes of activity five times a week as the bare minimum. "If you can do more," notes American College of Sports Medicine President Robert Sallis, a family physician at Kaiser Permanente in Fontana, Calif., "you get more benefits." Plus, the guidelines note that this activity is in addition to the "routine activities of daily life."

• How important is weight training? Very important. Muscle mass declines with age and is replaced with fat. Since fat burns fewer calories than muscle, metabolism gradually declines, which helps pile on the pounds.

Preserving muscle also makes it easier to perform everyday activities such as standing up from a chair or climbing stairs. The guidelines recommend doing eight to 10 exercises, such as french curls and crunches, to strengthen major muscles in the arms, legs and trunk. Repeat each exercise eight to 12 times. Rest one day between sessions to let muscles recover.

• Is exercise really going to help if I've been inactive lately? Sedentary people "have the most to gain just by getting up off the couch," says Sallis.

And forget about using age or illness as an excuse not to be active. A companion set of guidelines aimed at those 65 and older -- and at people aged 50 to 64 who have chronic health problems such as arthritis -- note that "virtually all older adults should be physically active" for the same 30 minutes five times a week.

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