A comparison of physical activity (high and low) and bone mineral density in young, healthy, eumenorrheic females

The comparison of chronically high (n = 37) and low (n = 37) levels of physical activity and bone mineral density (BMD) was investigated in young (12-22 years), healthy, eumenorrheic females. Subjects were placed into physical activity groups based on current and past physical activity patterns. Subjects in the high physical activity group currently engaged in an average of 10 hours per week of physical activity, while subjects in the low physical activity group exercised an average of 55 minutes per week. It was hypothesized that, regardless of measurement site, the high physical activity group would have a greater BMD when compared to the low physical activity group. Bone mineral density was obtained in the total body, lumbar spine (L1-L4), and proximal femur by dual-energy radiography, and the mid-shaft site of the bilateral radii by single photon absorptiometry. Additional measures of physique, body composition, nutritional intake, and caloric expenditure were obtained. The high physical activity group had significantly greater BMD than the low physical activity group at all measurement sites. After adjusting for weight, the significance between the physical activity groups remained in the lumbar spine, proximal femur, and femoral neck BMD. Additionally, adjustments for height resulted in a significant difference remaining in lumbar BMD. Weight, height, lean body mass, and several circumferences and skeletal widths correlated with lumbar spine, proximal femur, and total body bone mineral. The relationship between age and bone mineral measurements was linear at all of the measurement sites. There was no significant difference in the amount of calcium consumed between the physical activity groups. The results indicate that high levels of physical activity in young healthy females are associated with a greater BMD at several clinically important measurement sites, when compared to less active females, even after adjustments for size are made.U of I OnlyETDs are only available to UIUC Users without author permissio