The best prescription money can't buy

Conflicting recommendations on exercise obscure the main message: Just do it.

Of all the things you can do to stay healthy or get better, exercise tops the list.

What is there to love about physical activity? With apologies to Elizabeth Barrett Browning, let us count the ways. It guards against heart disease, eases existing heart disease, improves blood pressure and cholesterol, and keeps arteries flexible. Those are just for starters — the benefits extend far beyond the heart. Regular physical activity helps maintain normal weight, protects against diabetes, strengthens muscles and improves balance, wards off depression and anxiety, prevents osteoporosis, maintains memory and thinking skills, and reduces the risk of certain cancers. In a nutshell, people who exercise live longer — and better.

So why do only a minority of Americans take the elixir of exercise? It takes time, something we say we're short of even as the number of hours spent sitting in front a television or computer continues to climb. (Nielsen Media Research, the company that monitors the country's TV-viewing habits, says the average American now watches television more than four hours a day.)

Confusion about who benefits from exercise sidelines some people. Many individuals with heart disease logically assume that stressing the heart with exercise will make things worse. Not so — exercise usually stabilizes and strengthens the heart.

Apparently contradictory recommendations also get in the way. In the mid-1980s, the prevailing wisdom was that three to four hours of vigorous activity each week were needed to make a difference. Since then, we've heard that 20 minutes of exercise 3 times a week is right. Make that 5 times a week for 30 minutes. Scratch that, 10-minute bursts of activity a few times a day are okay. Hold on, now you need an hour a day. (All of these are right, but for different goals.)

Let's start with the clearest, simplest message possible: A little exercise or physical activity is better than none, and more is better than a little.

Four-part focus

Physical fitness begins to fade in your 40s. Aging saps staying power, strength, balance, and flexibility — four keys to good health and independence. You don't have to take this sitting down. Regular physical activity at any age can slow, or even turn back, the clock.

Stamina. Activities that make your heart beat faster and speed up your breathing are good for every part of your circulatory system. Sometimes called aerobic or endurance activities, they improve the heart's ability to circulate oxygenated blood and the body's ability to use oxygen. Such activities not only keep chronic diseases at bay but also help you carry out everyday activities like crossing a busy street or climbing a flight of stairs without stopping to catch your breath.

Strength. Building or strengthening muscle is good for you on many levels. It helps the body use blood sugar more efficiently, and so helps prevent or control diabetes. For many older people, stronger muscles stand between walking unassisted and using a walker, or between living independently and needing help for everyday activities.

Balance and flexibility. Uneven pavement, ruts in the lawn, wrinkled rugs, and a host of other hazards can trip you up. Good balance and flexibility can keep you from falling and breaking a leg, arm, hip, or shoulder. Falls and broken bones are leading causes of disability and loss of independence. Poor flexibility doesn't seem like a big deal, but it can interfere with your ability to drive, scratch your back, or cut your own toenails.

Does this mean you need four different exercise schedules? No. Walking and stretching most days of the week with weight lifting or strength training on the off days cover the bases.

Three hows and a what

How much? How often? How hard? What kind? These are the four most common questions people ask about exercise. The answers depend on who is asking, since an individual's health and current level of activity set the bar for the appropriate amount, intensity, and type of activity.

How much? Several long-term studies from Harvard and elsewhere have shown that health benefits from regular exercise or physical activity begin to kick in at about 700–1,000 purposefully burned calories a week. That means walking 7–10 miles a week (using 100 calories burned per mile as a rough rule of thumb). This represents a good target for inactive folks to work up to, and a decent minimum for everyone else. More is better, to a point. Cardiovascular and other benefits increase to about 2,000 calories burned a week. They level off after that.

How often? You don't take a week's worth of blood pressure pills at once; you spread them evenly over the course of a week. Treat exercise the same way. Being active every day or every other day is better for your body than one intense workout a week. (Even so, one is better than none.)

How hard? That depends on you. If you like to get sweaty and feel the burn, by all means run, chop wood, go whitewater kayaking, or turn the treadmill to high. If you don't, then walking and other less vigorous activities will fill the bill. A study from Duke University, published in the October 2005 Chest, showed that inactive, overweight men and women who walked 10 miles a week reaped the same cardiovascular benefits as those who ran the same distance.

Some people buy monitors that measure their heart rate as a way to check how hard they are working. Listening to your body is just as good. You are exercising moderately if your heart is beating faster than usual and you are breathing more quickly but can still carry on a conversation comfortably. (Next month we will look at exercise charts, sometimes used in stress testing, as measures of exercise intensity.)

What kind? This is a key question. Almost any kind of activity will do, cardiovascularly speaking. So pick one you'll enjoy and stick with. If you like repetition or watching television while you exercise, a rowing machine might be a good match. If you like to people-watch or see new sights, then walking around a pond or on a walking trail might suit you better.

Any time, any age

It is never too late to start exercising or become more physically active. In a key, long-term study of Harvard alumni, those who began exercising after age 45 were less likely to have died over an 11-year period than those who remained inactive. Frail octogenarians who take up strength training realize important gains in the muscle power needed to climb stairs or walk unassisted.

No matter what your age, weight, natural physical ability, or ailments, exercise can offer you something. The advice you heard so many times when you were young — "just go outside and play" — is as good for you today as it was when you were 10.