Effect of exercise intensity on bone density, strength, and calcium turnover in older women

Purpose: This study examined the effects of 24 wk of high intensity strengt h training or low intensity walking on lumbar bone mineral density (BMD), m uscular strength, and calcium turnover in Australian women either taking ho rmone replacement therapy (HRT) or not taking HRT. Methods: A subject pool of 64 women between 45-65 yr and randomly allocated into weights (N = 21), walking (N = 20), weightsHRT (N = 14), and walkingHRT (N = 9) groups comple ted this study. All subjects trained twice weekly in either a 50-min walkin g or weight-training program (60-90% 1RM). Measurements included maximal is ometric knee strength, 1RM bench press, 1RM squat, isokinetic back strength , lumbar (L2-L4) BMD, serum osteocalcin, and urinary deoxypyridinoline cros slinks (Dpd). Results: No significant group differences in BMD were evident at the completion of training. However, a significant (P < 0.05) within gr oup change was apparent for the walking group since BMD decreased 1.3% belo w baseline testing. Osteocalcin levels increased significantly (P < 0.05) i n the walking (22%) group. Maximal bench press and squat strength improved significantly (P < 0.05) in the weights (25.8% and 37.7%) and weightsHRT (2 5.4% and 35.7%) groups. The weights group also increased significantly (P < 0.05) in isokinetic back strength (22.2%). Conclusion: It was concluded th at short-term high intensity resistance training provides an effective mean s for increasing muscular strength in women between 45 and 65 yr. The train ing effects on lumbar BMD were not apparent in the present study.