3-YEAR CONTROLLED, RANDOMIZED TRIAL OF THE EFFECT OF DOSE-SPECIFIED LOADING AND STRENGTHENING EXERCISES ON BONE-MINERAL DENSITY OF SPINE AND FEMUR IN NONATHLETIC, PHYSICALLY ACTIVE WOMEN

The objectives of this study were to evaluate (1) the effect of spinal muscle strengthening by loading exercises on the bone mineral density (BMD) of the spine, and (2) the effect of upper extremity loading exe rcises on the BMD of the midradius and femur in healthy, premenopausal women, The study design was a randomized, controlled trial of 3 years ) duration, Ninety-six healthy, premenopausal, white women aged 30-40 years participated; 67 completed the study, All subjects were in good health (normal menses) and were active, but not athletic (that is, not involved in a regular sport activity), Subjects were randomized to an exercise or control group. The exercise group performed a supervised, nonstrenuous, weight-lifting exercise program, Exercise performance w as supervised once a week at the medical facility, In addition, the su bjects performed the exercises twice a week on their own, Dietary calc ium intake was to be maintained at 1,500 mg/day in both groups, Bone d ensity was measured at the lumbar spine and hip with dual-energy X-ray absorptiometry at 0, 1, and 3 years, BMD of the midradius was measure d with single photon absorptiometry, Measurements of muscle strength w ere obtained at baseline and every 3 months for 3 years, Maximal oxyge n uptake was measured, and the level of physical activity was recorded , Compliance with the exercise program was excellent during the first year of the study, but decreased thereafter, At the end of 3 years, su bject withdrawal was about 34% from the exercise group and about 22% f rom the control group (total subject withdrawal was about 30%), Muscle strength in the exercise group increased significantly at all involve d skeletal sites Ip values all < 0.001), There was a modest positive c orrelation between the BMD of Ward's triangle with spinal flexor stren gth (r = 0.32, p = 0.008) and with grip strength (r = 0.38, p = 0.001) , Comparing study groups, we found no significant effect of the loadin g and nonstrenuous strengthening exercises in the exercise group or fr ee physical activity group (our control group) on BMD at the spine, hi p, or midradius measurement sites, In active, but not athletic premeno pausal women, additional moderate weight-lifting exercises showed no s ignificant effect on BMD.