Physical Activity, Estrogen Replacement Therapy and Bone Mineral Density in Early Postmenopausal Women
The influence of high and low levels of physical activity on bone mineral content (BMC) and bone mineral density (BMD) was investigated in 60 healthy, Caucasian, early postmenopausal women. All women examined were a minimum of two but no more than five years past natural menstrual cessation. Subjects in the high physical activity group (n = 30) had an energy expenditure greater than 3000 kcal/week and in the low physical activity group (n = 30) less than 1500 kcal/week, estimated from walking, stair climbing, and sport and recreational activity participation. The physical activity groups were divided into two subgroups on the basis of use or avoidance of estrogen replacement therapy (ERT). It was hypothesized that the high physical activity group would have greater BMC and BMD values than the low physical activity group. It was further hypothesized that the high physical activity group would have greater bone mineral values when the interaction of ERT was considered and when plasma estrogen (estrone and estradiol) levels were statistically controlled. The bone mineral measurements were obtained from the total body, lumbar spine (L1-L4), and proximal femur by dual energy radiography. Additional measures of physique, body composition, nutritional intake and plasma estrogen level were obtained. The high physical activity group did not have significantly greater bone mineral content or bone mineral density than the low physical activity group regardless of the skeletal site examined. When the interaction of physical activity and ERT use was examined, and when the plasma estrogen levels were statistically controlled, the women in the high physical activity group did not have significantly greater bone mineral density than the less active group. Additionally, there were no significantly different bone mineral values at any of the skeletal sites when the ERT users were compared to non-ERT users. Stepwise multiple regression analyses revealed that the fat-free body weight was the most significant independent variable contributor to the resultant BMC and BMD measurements of the subjects. The results indicate that high levels of physical activity, alone or in combination with ERT, were not associated with greater BMC and BMD measurements during the early postmenopausal years. The findings suggest that increased levels of physical activity may not provide adequate protection against the hormonally-related bone loss characteristic of the early menopausal years.
Biology, Animal Physiology, Education, Physical, Health Sciences, General
University of Illinois - Urbana-Champaign
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University of Illinois at Urbana-Champaign