Lifetime physical activity is associated with bone mineral density in premenopausal women

Osteoporosis causes premature disability among millions of elderly people i n the United States, particularly women. Exercise helps to maintain bone ma ss, yet it remains unclear what type of physical activity during what age p eriods is most beneficial for bone mass and density. This cross-sectional s tudy investigated the relationship between different measures of lifetime p hysical activity and bone mineral density (BMD) in 25 premenopausal women ( mean age 41 years, range 28-50 years). BMD of the total, entire axial, and entire peripheral skeleton were measured by dual energy x-ray absorptiometr y (DXA). Lifetime history of physical activity was obtained by a structured interview, and estimates of lifetime weight-bearing exercise, total exerci se, total weight-bearing physical activity (including occupational and hous ehold activities), and perceived physical activity were computed. Adjustmen ts were made for current body weight and height and lifetime milk consumpti on. Lifetime weight-bearing exercise was significantly correlated with tota l and peripheral BMD (total BMD: r = 0.54; peripheral BMD: r = 0.54, all p < 0.05). Total weight-bearing physical activity, including occupational and household activity, was associated with total BMD (r = 0.51, p < 0.05). Ph ysical activity during early age periods was more strongly associated with BMD at all sites than was physical activity in the past 2 years. Our findin gs suggest that lifetime weight-bearing exercise is more strongly related t o BMD of the total and peripheral skeleton than is nonweight-bearing exerci se. The inclusion of nonweight-bearing activity resulted in a weakening of the association. Weight-bearing household and occupational activity appeare d to be related to BMD. Our results support recommendations to increase phy sical activity throughout life, particularly during early ages, as a means of osteoporosis prevention.