Calf Muscle Pump Stimulation Increases Lower Limb Bone Density in Perimenopausal Women

Nutrient delivery to bone tissue, as for all tissues in the body, is provided through interstitial fluid flow. This flow is driven by the differential fluid pressures between the intramedullary canal and the tissues outside of the bone. Correspondingly, reductions in tissue fluid pressure should enhance interstitial bone fluid flow, nutrient delivery, and thereby increase bone mineral density. This hypothesis was tested in a one year long pilot clinical study of healthy, employed, perimenopausal women (42 - 68 years). Soleus muscle (calf muscle pump) stimulation was utilized with the intent of increasing lower limb fluid return to the heart, serving to both reduce lower limb tissue pressures and to increase intramedullary pressures by increasing cardiac output. Dual-energy x-ray absorptiometry (DXA) assessments of bone mineral density (BMD) were obtained at 12 month intervals. Muscle stimulation usage ranged from 0.7 to 4.8 hours/work-day. Dose dependent responses between duration of daily soleus muscle stimulation and changes in both proximal femur BMD (+0.5% per hour of daily use; p = 0.05) and proximal tibia BMD (+1.5% per hour of daily use; p = 0.0004), were observed; no significant effect was observed at the lumbar spine. These results are consistent with the hypothesis that calf muscle pump stimulation, which is sufficient to reduce lower limb fluid pooling, is capable of significantly reducing the rate of bone loss in perimenopausal women as well as enhancing new bone formation.