Did you realize that our bones are made up of more than just calcium and protein? Bone contains active cells that continuously remove old bone and replace it with new bone in a process called remodeling. More than 10 million Americans have an imbalance in bone remodeling, causing the bone-thinning disease osteoporosis. Osteoporotic bones lose strength, become brittle, and result in approximately 1.5 million fractures a year.
What Are the Risk Factors for Osteoporosis?
- Advanced age — Bone loss occurs in adulthood, beginning in middle age and accelerating during menopause.
- Female gender — Women have less bone mass than men, so any decline over time will affect women more.
- Early menopause — Estrogen helps keeps bones strong. The younger a woman experiences menopause, the more rapidly she loses the benefits of estrogen.
- Corticosteroid use — People who need to take medications such as prednisone, prednisolone or dexamethasone regularly are prone to accelerated bone loss.
- Smoking — Tobacco use accelerates loss of bone, especially in women.
- Alcohol — Overuse of alcohol increases the chance of developing osteoporosis.
- Low body weight — Underweight women often have lower bone mass than heavier women at similar ages.
- Inadequate intake of calcium and vitamin D — Both are necessary to allow bones to remodel properly.
- Lack of physical activity — Exercise is now recognized as a key factor in maintaining bone health.
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Why Exercise for Strong Bones?
Most people are aware of the need for calcium to maintain healthy bones, but many overlook the great benefits that exercise can yield to sustain healthy bones and prevent falls and fractures. Weight-bearing exercises, defined as activities that place compressive forces on bone, are especially helpful in preventing bone loss. Young female athletes, like runners, who engage in aerobic activities that place compressive forces on bone have greater bone mineral density (BMD) than sedentary people. In general, the intensity, frequency and duration of exercise correlate with benefits, as long as young women don't overdo it.
A good exercise routine for healthier bones puts positive stress on multiple parts of the body. The bones at greatest risk of fracture include the spine, hip, and radius (one of the bones in the forearm). Exercises designed to put loading forces on specific sites provide a crucial workout to these most vulnerable bones. These types of exercises compress and extend the muscle groups around bones, creating loading force.
You can get a greater increase in bone mineral density (BMD) with high-intensity resistance training compared with low-intensity. Casual walking provides a loading force equal to body weight and usually is not enough to improve BMD. Walking briskly will help a little more. Better options for high-intensity exercise (other than weights) to improve BMD include jumping, running and high-impact aerobic dance for 20 or more minutes for at least three times per week. The goal of resistance training is to load forces of three or four times body weight.
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What Is Included in a Good Resistance-Training Program?
High-intensity resistance training requires repetitions with weight that feels somewhat heavy and cannot be easily lifted over and over. For weights, you can use elastic bands, free weights or other objects around the house such as cans or bags of beans. The components of vigorous resistance training include:
- Frequency — Two or three days a week
- Intensity — Eight to 12 repetitions with weight that cannot be lifted more than 12 times
- Duration — Two or three sets of each exercise
- Progression — Increase weight by about 10% when 12 repetitions can be done
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Some Sample Exercises for Target Areas
Spine — Back extensions
A simple back extension exercise: Lie on stomach with forehead resting on floor or rolled up towel. Extend arms straight in front of head. Raise head off the floor a few inches. Hold for several seconds. Do three sets of eight to 12 repetitions Another option is to lie with towel roll under head and pillow under hips. Raise head, arms, and legs off floor. Hold for several seconds. Do three sets of eight to 12 repetitions.
Hip — Squats, thigh adduction/abduction exercises with elastic bands or weights
Forearm — Bicep curls, wrist curls, reverse wrist curls
Include a variety of exercises for all major groups to promote well-balanced muscle development. Improved muscle strength also enhances coordination and balance to protect against falls. While working on your resistance training program, don't forget simple exercises to improve balance such as tandem walking (walking heel to toe) or sitting on a stability ball.
Remember, an active lifestyle is an effective strategy to maintain skeletal health throughout your lifespan. Make it a priority to find time every day for exercise. Your bones will thank you for it.
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Paulette Chandler, M.D., M.P.H., is a clinical instructor of medicine at Harvard Medical School and an attending physician at Brigham and Women's Hospital.