I used to think of exercise as an all-or-none phenomenon. On any given day I either did something strenuous, like running or hiking, or I rested. But now that I'm older (and hopefully wiser), my body doesn't like either extreme. I feel and function better with daily amounts of moderate activity.

Recently, scientific research has confirmed the value of this type of routine. Fitness experts now advocate that for optimum health, adults should get at least 30 minutes of moderate-intensity exercise on most, if not all, days of the week. (A moderate level of exercise is defined as that which burns 150 calories a day, or 1,050 calories each week.) Physical activities can be performed at one time or spread throughout the day.

The health benefits that come from this kind of commitment to exercise are astounding. Studies show that staying fit can help lower your blood pressure and cholesterol; reduce your risk of heart disease, cancer, and diabetes; preserve your bones and joints; prevent muscle loss and weight gain; improve your mood, memory, and sleep; and prolong your life. The list goes on, but let's get down to the nitty-gritty: Exactly how much exercise do you need to achieve good health?

Recommendations for getting FITT

The American College of Sports Medicine makes the following recommendations for the types and amounts of exercise you need for overall health and fitness:

Exercising your options

If sweating on a stationary bike just isn't your style, take heart. Whether you prefer shooting hoops or gardening, there are plenty of activities you can incorporate into your daily routine. The National Heart, Lung, and Blood Institute offers tips on ways to include more moderate-intensity exercise in your lifestyle. As the table below shows, more strenuous activities should be done for a shorter amount of time, while less strenuous activities should be done for longer. To avoid injury, start slowly and gradually increase your intensity.

Precautions before you begin

Physical activities can stress your body and heart, so get clearance from your health care provider before starting an exercise program. This is especially important if you are physically inactive; overweight; over age 40; acutely or chronically ill from heart, lung, or other diseases; or if you have risk factors for heart disease, such as smoking, high cholesterol, high blood pressure, diabetes, or a family history of heart disease.

Elizabeth Smoots, M.D., F.A.A.F.P., is a board-certified family physician in Seattle, Washington. A fellow of the American Academy of Family Physicians, Dr. Smoots specializes in prevention and primary care medicine.