Lower extremity loads stimulate bone formation in the vertebral column: implications for osteoporosis.

Senile osteoporosis is a growing national health problem. The purpose of this study was to determine whether loads applied through the lower extremity would stimulate bone formation in the vertebral column, the site of most osteoporotic fractures. Female white New Zealand rabbits were divided into experimental (EG) and control (CG) groups. The right hind leg of the EG was repetitively loaded to 1.5 X body weight, 20 min/day for three weeks; the CG was "sham loaded". Bone formation in both groups was labeled using tetracycline. Labeled osteons, resorption spaces, surface bone formation, and porosity were measured in cross-sections from the right and left tibias and humeri, right femurs, and L6, L1, T12, T1, and C7 vertebrae. This experiment demonstrates that repetitive loading of the lower extremity increases osteonal bone formation in the vertebral column of rabbits extending at least up to the cervical spine, but not into the forelimbs. This finding supports the concept that exercise involving repetitive loading of the lower limbs (eg, walking) could be used to treat or prevent age-related osteoporotic changes in the vertebrae.