If you want strong bones, you have to use them! Everyone needs lifelong weight-bearing exercise to build and maintain healthy bones. Girls and young women especially should concentrate on building strong bones now to cut their risk of osteoporosis later in life.

A bone thinning disease that can lead to devastating fractures, osteoporosis afflicts many women after menopause and some men in older age. Osteoporosis is responsible for almost all the hip fractures in older people.

The disease is largely preventable if you get enough weight-bearing exercise when you're young, stay active and continue other healthy habits as you age.

The maximum size and density of your bones (peak bone mass) is determined by genetics but you need weightbearing exercise to reach top strength. The best time to build bone density is during years of rapid growth.

• Weight-bearing exercise during the teen years is ideal.
• Bones continue to grow during the 20s and sometimes into the early 30s. (Bone loss normally begins in the mid-30s.)
• Smoking and excessive alchohol use can decrease bone mass.

Osteoporosis prevention is a special concern for females for a number of reasons:

• Women generally reach peak bone mass at an earlier age than men.
• Peak bone mass tends to be lower in women than in men.
• Pregnancy and breast feeding can lower bone mass.
• Women undergo rapid bone loss after menopause when levels of the bone strengthening hormone estrogen drop dramatically. (The removal of ovaries will have the same effect on bone mass.)

Doing regular weightbearing exercise for the rest of your life can help maintain your bone strength.

Weightbearing describes any activity you do on your feet that works your bones and muscles against gravity. Bone is living tissue that constantly breaks down and reforms. When you do regular weightbearing exercise, your bone adapts to the impact of weight and pull of muscle by building more cells and becoming stronger.

Some activities recommended to build strong bones include:

• Brisk walking, jogging, and hiking.
• Yard work such as pushing a lawnmower and heavy gardening.
• Team sports, such as soccer, baseball, and basketball.
• Dancing, step aerobics, and stair climbing.
• Tennis and other racquet sports.
• Skiing, skating, karate, and bowling.
• Weight training with free weights or machines.

Although they are excellent cardiovascular exercise choices, swimming and bicycling are not weightbearing activities, so are not as effective as the above activities in adding bone mass. If musculoskeletal conditions prevent weight-bearing exercise, then swimming and cycling are good alternatives. They do have some bone-building capacity.

You should exercise for at least 30 minutes a day, four or more days a week. Besides improving bone strength, regular exercise also increases muscle strength, improves coordination and balance, and leads to better overall health. To sustain the bone strengthening benefit of weightbearing activity, you must increase the intensity, duration and amount of stress applied to bone over time.

In addition to doing weightbearing exercise, to protect yourself from osteoporosis, you should also:

• Eat a diet rich in calcium and vitamin D. This may include dairy products (i.e., milk, yogurt and cheese), vegetables (i.e., spinach and broccoli) and fish (i.e., sardines). Because it is difficult to meet the daily requirement through diet alone, calcium and vitamin D supplements are recommended.
• Practice a healthy lifestyle with no smoking or excessive drinking.
• See your doctor for a bone density test and/or medications as necessary.

Premenopausal women who exercise too much or suffer from the eating disorder anorexia nervosa can also develop long term problems with weak bones if low body weight stops normal menstrual periods (amenorrhea). If this happens during rapid growth years, you could lose bone mass at a time when your body needs to be building it. See your doctor right away for diagnosis and treatment.

For more information, see the web site of national bone health campaign, Powerful Bones, Powerful Girls by the Department of Health and Human Services, Centers for Disease Control and Prevention and the National Osteoporosis Foundation: Powerful Bones, Powerful GirlsPowerful Bones, Powerful Girls (http://www.cdc.gov/powerfulbones/)

The AAOS Women's Health Issues Committee strongly supports the campaign.