Physical activity is an essential factor in bone health. The skeletal benefits of exercise have been demonstrated throughout the life cycle. Exercise can positively affect peak bone mass in children and adolescents; has been shown to help maintain or even modestly increase bone density in adulthood and; can assist in minimizing age related bone loss in older adults.
Exercise and Peak Bone Mass
By age 18, skeletal growth is nearly complete. The amount of peak bone mass achieved and the subsequent rate of bone loss are the key determinants of bone density later in life. There is substantial evidence that exercise plays an important role in the acquisition of bone mass in youth. Activities that are high impact and weight-bearing, such as running, jumping, soccer and volleyball, appear to be the most beneficial to the skeleton. The gains of such weight-bearing activity seem to be more pronounced in the peripheral skeleton than in the lumbar spine.
Muscle strengthening can also yield a bone-building effect. Even muscle activity in areas distant from the spine and hip can positively impact bone density at these sites. Not all physically active youth reap the skeletal benefits of exercise. Girls and young women who experience a disruption in the menstrual cycle from excessive exercise can endure bone loss that is never fully recovered (it is estimated that the prevalence of amenorrhea in female athletes ranges from 10-45 percent.) There is much concern that these young women are at an increased risk of stress fractures and fractures of the hip and spine.
Clearly, several factors other than exercise can affect peak bone mass. Hormonal status, body composition, nutritional intake and medication use are also important predictors of bone density.
Physical Activity in Adult Women
While 97% of bone mass is probably achieved by the age of eighteen, increases in bone density have been observed throughout the third decade of life. In some cases, even moderate increases in physical activity of women in their twenties can increase bone density and, potentially, decrease long-term fracture risk.
Most studies of pre-menopausal women demonstrate a positive bone benefit from exercise, with greater loading and higher impact activities producing the greatest skeletal benefit. The effects of physical activity tend to be the most pronounced among individuals who are the least active, an observation that has been made in other age groups, as well.
The Postmenopause and Beyond
Exercise continues to confer a skeletal benefit for many postmenopausal women. However, there is no evidence that physical activity alone is sufficient to fully offset the damaging effects of estrogen withdrawal in the first three to five years following menopause. Once the phase of accelerated bone loss is complete, regular exercise can have a protective effect on bone. As with other age groups, active postmenopausal women tend to have greater bone density than sedentary postmenopausal women.
Due to musculoskeletal concerns, older women are less likely to participate in higher impact activities. Regular activity such as walking, weight training and low impact aerobics can safely help to offset age-related bone loss, decrease fracture risk and improve the quality of life for older women.
Prevention of Falls and Fracture
Skeletal muscle mass and strength also decrease with age. Increased muscle weakness can compound the problem of low bone density by increasing the risk of falls and fracture. A multi-center study funded by the National Institute on Aging has evaluated the effects of intervention programs designed to minimize fracture risk in the elderly. The FICSIT trials (Frailty and Injuries: Cooperative Studies of Intervention Techniques) evaluated the effects of various physical activities in reducing the risk of falls. Strategies such as resistance training, computerized balance training and Tai Chi have shown promise as effective interventions for reducing falls and fall-related fractures.
Article Courtesy of the United States National Institute of Health
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