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Reviewed May 2009
Like muscle, bone is living tissue that responds to exercise by becoming stronger. Young women and men who exercise regularly generally have greater bone mass (bone density and strength) than those who do not. For most people, bone mass peaks by the late twenties. After the age of 30, women and men can help prevent bone loss with regular exercise. The best exercise for bones is weight-bearing exercise. This is exercise that forces you to work against gravity, such as walking, hiking, jogging, climbing stairs, playing tennis, dancing, and lifting weights. Swimming and bicycling are examples of non-weight-bearing exercises.
Although weight-bearing activities contribute to the development and maintenance of bone mass, weightlessness and immobility can result in bone loss. Space travel has provided significant research data on the subject of weightlessness and bone loss. Astronauts exposed to the microgravity of space experience significant bone loss, leaving their bones weak and less able to support the body's weight and movement upon return to Earth.
Some people can't perform weight-bearing activity. They include, for example, people who are on prolonged bed rest because of surgery, serious illness, or complications of pregnancy; and those who are experiencing immobilization of some part of the body because of stroke, fracture, spinal cord injury, or other chronic conditions. These people often experience a significant bone loss and are at high risk for developing osteoporosis and having a fracture.
Bone loss typically occurs over several months and then gradually levels off as the bones adjust to the state of weightlessness.
In general, healthy people who undergo prolonged periods of bed rest or immobilization can regain bone mass when they resume weight-bearing activities. Studies suggest that there is a good chance to fully recover the lost bone if the immobilization period is limited to 5 to 10 weeks. Additionally, even brief intervals of weight-bearing activity during periods of limited mobility or bed rest can help lessen bone loss.
The greatest concern is for people who cannot resume weight-bearing activities and therefore typically do not regain lost bone density. Studies suggest that taking an osteoporosis treatment medication and reducing or eliminating other risk factors for osteoporosis can help slow the rate of bone loss.
This publication contains information about medications used to treat the health condition discussed here. When this fact sheet was printed, we included the most up-to-date (accurate) information available. Occasionally, new information on medication is released.
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