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Half an Hour for Health

By Sally Squires
Tuesday, August 14, 2007

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 (ACSM) and the American Heart Association have just set the bar lower.

How low?

The groups recommend 30 minutes of brisk walking -- or similar moderately intensive physical activity -- five times per 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 ACSM and the Centers for Disease Control and Prevention.

Confused? You're not alone. Exercise researchers have debated the subject for more than a decade -- and the new guidelines are intended clarify what seems like conflicting advice.

Here are some questions you might find yourself asking 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 by the Institute of Medicine, but it was set to help people control their 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, the new -- that is to say, the old -- 30-minute standard seems to do the trick.

"That's the bottom line," says Steven N. Blair, a professor of exercise science at the University of South Carolina and co-chair of the committee that drafted the latest guidelines. "This is the amount of activity that provides really substantial health benefits."

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 them are lower blood pressure, better control of blood sugar and less insulin resistance -- a condition that often precedes Type 2 diabetes. Also, improvements in blood fat levels, such as triglycerides, which hike heart disease risk. There's also less inflammation, which also appears to help cut heart disease risk and may improve arthritis and other conditions. Blood vessels also seem to be able to control blood flow better with regular activity -- that helps to cut the odds of having a heart attack -- and there's less risk of forming blood clots, which can lead to stroke.

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 per day produces the same benefits as getting 30 minutes of moderate activity at once.

Are there other options? You bet. Choice is one of the new features of the guidelines, which 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 for the day? Technically, yes. But the more active you are, the better. Consider 30 minutes of activity five times per week as the bare minimum. "If you can do more," notes ACSM 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."

I'm not sure about the advice to lift weights. I don't want to look like a bodybuilder, so how important is that? Not to worry. Weight training a couple of times a week won't turn you into Arnold Schwarzenegger. What it will do is help preserve your muscles. That's a good thing, because we all lose muscle mass with age. Fat replaces the muscle. Since fat burns fewer calories than muscle, our metabolism gradually declines, which helps pile on the pounds.

Preserving muscle also makes it easier to perform everyday activities such as getting out of your chair, climbing stairs and carrying groceries without huffing and puffing. The guidelines recommend doing eight to 10 exercises, such as triceps curls and crunches, to keep major muscles in the arms, legs and trunk strong. Do eight to 12 repetitions of each exercise and make sure to rest one day before lifting weights again, to give your muscles a chance to recover.

Okay, but it's been a long time since I've exercised. Am I really going to feel better from getting more activity? Sedentary people "have the most to gain just by getting up off the couch," says Sallis, who is leading an ACSM effort to get all physicians to prescribe activity to their patients at every visit.

And forget about using age as an excuse to be inactive. The ACSM and the American Heart Association issued a companion set of guidelines aimed at people 65 and older (and for those 50 to 64 with chronic health problems such as arthritis and diabetes). They say "virtually all older adults should be physically active" for 30 minutes five times per week.

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