Strength training effects on bone mineral content and density in premenopausal women

Mechanical loading, such as that seen with physical activity, is thought to be the primary factor influencing bone strength. Previous randomized studies that assessed the effect of strength training on bone in premenopausal women report inconsistent results. The analysis herein examines the effect of a strength training program following published guidelines (US Department of Health and Human Services) on bone mineral content (BMC) and areal bone mineral content (aBMD) in the proximal femur and lumbar spine in premenopausal women.

One hundred and forty-eight overweight, sedentary, premenopausal women aged 25-44 were randomized to progressive strength training (ST, n = 72) or standard care (CO, n = 76) for 2 yr. Measurements occurred at baseline, 1 yr, and 2 yr. Proximal femur and lumbar spine BMC and aBMD were measured by dual energy x-ray absorptiometry. Intention-to-treat analyses were completed, and repeated-measures ANCOVA adjusted for baseline height and weight was used to assess the effect of strength training on bone.

aBMD showed little change and did not differ between groups at any site. Femoral neck BMC showed a significant difference in the slopes between ST and CO (P = 0.04) with no change in the ST group and a 1.5% decrease in the CO. There were no significant between-group differences at any other measurement site.

Strength training had no effect on aBMD after 2 yr of strength training. Femoral neck BMC decreased in CO and had no change in ST. Because there was no change in aBMD, strength training may have influenced bone size. Research to better understand changes in bone dimensions and geometry with strength training in premenopausal women is warranted.