Blood flow, histomorphology and elemental composition of the canine femur after physical training or immobilization

Effects of long-term physical training (treadmill running 4 km/day for 15 weeks) and immobilization (casting of the limb for 11 weeks) on the blood flow, bone marrow uptake of radio-colloid, histomorphology as well as elemental composition of the proximal canine femur were investigated. In the runners both bone marrow and mean bone perfusions measured with a 133Xe washout method were increased by 53.5% (P less than 0.05) and 54.1% (P less than 0.05), respectively, as compared with the age-matched controls. Bone marrow uptake of [99mTc]tincolloid and volumetric fractions of trabecular bone and bone marrow were not significantly altered after training or immobilization. The amount of zinc measured by atomic absorption spectrophotometry was, however, significantly higher (P less than 0.01) after immobilization as compared with the controls. Consequently, long-term physical training is suggested to stimulate bone metabolism by enhancing its blood perfusion even in the resting state, whereas the increase of zinc content was considered to be linked to the obvious bone resorption caused by immobilization.