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You Asked for It: Question Authority

Nieman, David C. Dr.PH, FACSM

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David C. Nieman, Dr.PH, FACSM, is Professor and Director of the Human Performance Laboratory, Appalachian State University, in Boone, NC, an active researcher, and author of several textbooks on health and fitness.

Q: Is walking considered effective in preventing and treating osteoporosis?

A: This is a good question that has a new answer: no. It is becoming increasingly apparent that physical activities such as walking do not place enough stress on the bones to improve their strength. Results from several studies investigating the effects of walking show that this activity, which is recommended commonly for postmenopausal women to lower heart disease risk, does not prevent bone loss. Physical activities of higher intensity and weight lifting have a more positive effect on the skeleton. Before reviewing this evidence further, let's learn more about osteoporosis.

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What Is Osteoporosis?
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Osteoporosis is a bone-weakening disease that develops gradually and makes bones so fragile that they fracture under normal use (1). Osteoporosis is a silent disease that progresses without any outward signs, sometimes for decades, until a fracture occurs. These broken bones are often caused by a minor fall or bump that would not normally cause a break. The sites most commonly affected are the spine, hips, and forearms.

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Prevention of Osteoporosis

Building strong bones, especially before the age of 35, and then reducing bone loss in later years, are the best strategies for preventing osteoporosis (1). Several risk factors predict those who should be most concerned about prevention of osteoporosis:

* Age. The older an individual, the greater the risk of osteoporosis, with most experiencing loss of bone mass starting in the fifth decade.

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* Gender and race. Women are at greater risk for developing osteoporosis than men (four to one). Caucasian and Asian women are more likely to develop osteoporosis than women in other racial groups.

* Bone structure and body weight. Small-boned and thin women are at greater risk than other women.

* Menopause/menstrual history. Normal or early menopause increases osteoporosis risk.

* Lifestyle. The chances of developing osteoporosis increase by smoking, drinking too much alcohol, ingesting too much caffeine, protein, or salt, consuming an inadequate amount of calcium, and getting little or no weight-bearing exercise.

* Medications and disease. Osteoporosis is associated with certain medications (e.g., cortisone-like drugs, steroids, thyroid hormone, and long-acting sedatives) and is a recognized complication of a number of medical conditions and prolonged bed rest.

* Family history. Susceptibility to fracture may be, in part, hereditary.

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Treatment of Osteoporosis

There is no cure for osteoporosis, but several strategies can help slow its progress (1,2):

* Diet. Achieving an adequate intake of calcium and vitamin D is important for skeletal health. Emphasize a high intake of calcium from dairy products, calcium-fortified foods, and calcium supplements. The target daily intake for older women is 1,200-1,500 mg of calcium and 400-600 IU of vitamin D. Fluoride is no longer considered an appropriate therapy for osteoporosis because it seems to make the bones more brittle.

* Medications. Bisphosphonates (e.g., risedronate and alendronate) are the drug treatment of choice for patients at high fracture risk. The documented risk of long-term estrogen/progestin therapy significantly detract from its usefulness for the prevention or treatment of osteoporosis.

* Exercise. A near-daily program of vigorous aerobic and resistance exercise involving all of the major muscle groups is recommended for both preventing and treating osteoporosis (3). Exercising early in life maximizes the peak bone mass attained in youth, whereas exercise later in life reduces age-related bone loss and preserves muscle strength to reduce the risk of falling.

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The Exercise Connection

When force or stress is applied to a bone, the bone bends. This sets up a cascade of events that stimulates cells to strengthen the bone. The bone can adapt to stress or the lack of it by forming or losing mass. For the bone to become bigger and more dense, the stress must be above and beyond normal levels. The bone will continue to grow and adapt until it is restructured to handle the new imposed stress (1-5).

Each bone in the body must be stressed to grow strong. If the leg bones are stressed by running and jumping, the arms bones will not benefit unless they too are stressed with specific exercises (e.g., weight lifting). Thus a good exercise program to prevent and treat osteoporosis involves all of the major muscle and bone groups in the entire body (6).

Physical activities such as walking or swimming do not place enough stress on the bones to improve their strength. Activities such as team sports, running, and racket sports, where the weight of the body is borne by the feet and legs during vigorous movements, are more effective in maintaining density of the leg and spinal bones than non-weight-bearing activities such as bicycling and swimming (4,5).

Young bone is more responsive to exercise stress than old bone. Given that approximately 60% of the final skeleton is built during adolescence, vigorous physical exercise during childhood and adolescence is more important than at any other time in life (5). Among older women, a history of lifelong physical activity relates to a greater bone mineral mass and, importantly, a lowered risk of hip fracture. Muscle strength is an important predictor of strong and dense bones among older adults.

Exercise alone cannot prevent or cure osteoporosis. ACSM adds that although "weight-bearing physical activity is essential for the normal development and maintenance of a healthy skeleton …exercise cannot be recommended as a substitute for hormone replacement therapy at the time of menopause" (6). In other words, osteoporosis prevention and treatment demands a multifaceted approach through diet, exercise, and appropriate medications.

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Exercise Programming

If you are an exercise trainer working with elderly individuals at risk for osteoporosis, first consult the individual's physician and physical therapist to plan a safe and appropriate exercise program. Instead of emphasizing just walking, organize a well-balanced exercise program with cardiovascular, strength, and flexibility activities. Persons with osteoporosis are often unfit, and orthopedic limitations may slow progress and mandate the use of supports during exercise. Prevent falls during exercise by using wall railings and making the exercise environment free of hazards such as loose floor tiles, mats, and exercise equipment.

Focus upon weight-bearing activities such as treadmill walking and stair climbing to help build bone mass. Start with 10-15 minutes of low- to moderate-intensity cardiovascular activity 3 days per week, and slowly build up to 30 or more minutes of moderate- to vigorous-intensity activity on most days of the week. Use support as needed.

Weight training activities for the legs, abdomen, and back should be emphasized to improve lower-body strength and posture to help prevent falls and broken bones. Use traditional weight machines and weight belts to ensure safety during training.

Choose 2 to 3 muscle groups to train each workout. Rest a minimum of 48 hours between working the same muscle. Begin the program with one set at 10 to 15 repetitions. Gradually progress to 2 to 3 sets at 6 to 10 repetitions to build strength, adding additional exercises as tolerated. Engage in static stretching and range-of-motion calisthenics after each cardiovascular and strength training session.

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References

1. McClung, M.R. Prevention and management of osteoporosis. Best Practice and Research Clinical Endocrinology and Metabolism 17(1):53-71, 2003.

2. Murphy, F.T., A.J. Kivitz, and E.E. Sands. Management of postmenopausal osteoporosis. Journal of the American Osteopathic Association 103(10 Suppl 6):S6-11, 2003.

3. Beck, B.R., and C.M. Snow. Bone health across the lifespan-exercising our options. Exercise and Sport Sciences Reviews 31(3):117-122, 2003.

4. Kemmler, W., K. Engelke, J. Weineck, et al. The Erlangen Fitness Osteoporosis Prevention Study: a controlled exercise trial in early postmenopausal women with low bone density-first-year results. Archives of Physical Medicine and Rehabilitation 84(5):673-682, 2003.

5. Sear, S.J., A. Prentice, S.C. Jones, and T.J. Cole. Effect of a calcium and exercise intervention on the bone mineral status of 16-18-y-old adolescent girls. American Journal of Clinical Nutrition 77(4):985-992, 2003.

6. American College of Sports Medicine position stand. Osteoporosis and exercise. Medicine & Science in Sports & Exercise® 27(4):i-vii, 1995.

© 2004 American College of Sports Medicine

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