Weight lifted in strength training predicts bone change in postmenopausal women

Purpose: The aim of this study was to examine the relationship between weight lifted in 1 yr of progressive strength training and change in bone mineral density (BMD) in a group of calcium-replete, postmenopausal women. Methods: As part of a large clinical trial, 140 calcium-supplemented women, 44-66 yr old, were randomized to a 1-yr progressive strength-training program. Half of the women were using hormone replacement therapy. Three times weekly, subjects completed two sets of six to eight repetitions in eight core exercises at 70-80% of one repetition maximum. BMD was measured at baseline and 1 yr. Results: In multiple linear regression, the increase in femur trochanter (FT) BMD was positively related to total weight lifted (0.001 g·cm^-2 for a SD of weight lifted, P<0.01) after adjusting for age, baseline factors, HRT status, weight change, cohort, and fitness center. The weighted squats showed the strongest (0.002 g·cm^-2 for a SD of weight lifted, P<0.001), whereas the back extension exhibited the weakest (0.0005 g·cm^-2 for a SD of weight lifted, P<0.26) association with change in FT BMD. The amount of weight lifted in the weighted march exercise was significantly related to total body BMD (0.0006 g·cm^-2 for a SD of weight lifted, P<0.01). The associations between weight lifted and BMD for the femur neck or lumbar spine were not significant. Conclusion: Evidence of a linear relationship between BMD change and total and exercise-specific weight lifted in a 1-yr strength-training program reinforces the positive association between this type of exercise and BMD in postmenopausal women.