Weight-bearing exercise, overexercise, and lumbar bone density over age 50 years.

This cross-sectional study of 78 healthy subjects older than age 50 years was designed to examine the association between weight-bearing exercise and lumbar bone mineral content as assessed by quantitative computed tomography. In women, a strong correlation existed between bone density and the amount of exercise for up to 300 min/wk. However, 5 of 28 women exercising 300 min/wk or more had surprisingly low bone density, not explained by other factors. In 50 men, we also found a strong positive correlation between exercise and bone density for those up to age 65 years. Over age 65, 3 men had low bone density despite extremely vigorous exercise. We conclude that moderate weight-bearing exercise may increase lumbar bone density, but we raise the hypothesis that extremely vigorous exercise actually may be detrimental to bone density in individuals after age 50.