Current Physical Activity is Related to Bone Mineral Density in Males but not in Females

The purpose of the present study was to investigate the association between high-, medium-, and low-impact physical activity in males and females at the time of peak bone mineral density in young adulthood. The cohort consisted of 62 male medical students (aged 28.1 +/- 3.9) and 62 female medical students (aged 25.1 +/- 3.9). The bone mineral density (aBMD, g/cm (2)) of the total body, femoral neck, and lumbar spine, and the bone mineral content (BMC, grams) and area (cm (2)) of the femoral neck and lumbar spine was measured using dual energy X-ray absorptiometry. Volumetric BMD (vBMD, mg/cm (3)) of the femoral neck and lumbar spine was estimated. The total amount of physical activity per week, which was recorded in a questionnaire, was divided into high-impact, medium-impact, and low-impact activity. In the male cohort, hours of high-impact physical activity per week was associated with aBMD and BMC of all sites (r=0.27 - 0.53, p<0.05) and bone area of the femoral neck (r=0.38, p<0.01). Total amount of physical activity per week was associated with aBMD of the total body and femoral neck, BMC of femoral neck and lumbar spine, femoral neck vBMD, and the lumbar spine area (p<0.05 for all). Using multiple linear regression, high-impact physical activity was independently associated with aBMD (beta=0.27, p<0.05) and BMC (beta=0.34, p<0.01) of the femoral neck. In the female cohort there was no association between amount or type of physical activity to aBMD, BMC, vBMD, or the bone area of any site. Instead body weight, lean body mass, or fat mass were significantly related to aBMD and all BMC sites in this group. The results of the present study suggest that present physical activity level has a stronger relation to different aspects of bone mass in the male compared to the female adult skeleton.