Mechanical loading attenuates loss of bone mass and bone strength induced by immobilization and calcium-deficiency

Due to the character of the original source materials and the nature of batch digitization, quality control issues may be present in this document. Please report any quality issues you encounter to digital@library.tamu.edu, referencing the URI of the item.Includes bibliographical references.Issued also on microfiche from Lange Micrographics.Immobilization and calcium-deficiency have been documented to cause a decrease in strength and bone mineral loss, and exercise is known to strengthen bone. The purpose of this study was to determine the effects of mechanical loading on parameters of bone mass and bone strength in bone subjected to immobilization and calcium-deficiency. Adult female rats were randomly assigned to either a control group (C), immobilized (I) group or an immobilized-loaded (IL) group. The C group had no immobilization and were fed a regular rat chow containing 1.85% calcium. The I group had one hindlimb immobilized by taping and fed a low calcium diet containing 0.01% calcium. The IL group had the same treatment as the immobilized group but had the immobilized limb mechanically loaded by a unique four-point loading machine three times per week. After six weeks of treatment, all animals were sacrificed, both tibia removed and tested for bone mineral density (BMD) by dual energy X-ray absorptiometry, stiffness and ultimate load by three-point bending to failure, cross-sectional moment of inertia, cross-sectional area, and modulus of elasticity. All comparisons were done by one-way ANOVA. When results were found to be significant, Student Newman-Keuls Method post hoc tests when performed. Final results indicate: 1. Six weeks of immobilization by taping and calcium-deficient diet ( I group) decreased cortical BNM by 12%, ultimate load by 19@o and stiffness by 19.77o, when compared to control rats.2. External loading at 34N, 36 cycles @ 2 Hz, three times per week attenuates the decrease in BMD and ultimate load in this model. The IL group mean BMD was only 2.37o lower than the control group mean, and ultimate load was 107o lower than the control group. 3. In this model significant correlations were found between BMD and ultimate load (r=0.754) and BMD and stiffness (r=0.793). This indicates BNM is an effective predictor of bone functional properties in this model