Dose-response effect of 40 weeks of resistance training on bone mineral density in older adults

Resistance training is becoming popular for maintaining bone health. Previous studies examined high intensity exercise; we compared high and low intensity resistance training performed 2 or 3 days per week in older adults. We found positive bone density responses for the hip and spine for all types of resistance training. This study determined the dose-response effect of resistance training on lumbar spine, proximal femur, and total body bone mineral density (BMD) in older men and women (55-74 years). Subjects included 45 men and 79 women who were assigned to one of the following training groups: 1-high intensity (80% 1RM), 2 days/week (2HI); 2-low intensity (40% 1RM), 2 days/week (2LI); 3-high intensity (80% 1RM), 3 days/week (3HI); and 4-low intensity (40% 1RM), 3 days/week (3LI). Bone scans (dual energy X-ray absorptiometry) were performed at baseline and after 40 weeks of training. Muscular strength (1-repetition maximum) was assessed every 5 weeks. There were significant trial (p < 0.05) effects but no significant trial x training group interactions for the BMD sites. Spine, trochanter, and total hip BMD increased from baseline to 40 weeks; however, the total body BMD site decreased in the 3LI group. Men and women exhibited similar improvements for the trochanter and total hip sites but the percent change in the spine tended (p = 0.054) to be higher for men (1.8%) than women (0.4%). The resistance training programs, regardless of intensity and frequency, were effective in improving BMD of the proximal femur and lumbar spine but not the total body. Both men and women responded similarly for the hip sites but men show a greater response at the lumbar spine than women.