Assessment of bone response to conditioning exercise in the radius and tibia of young thoroughbred horses using pQCT.

OBJECTIVES To assess the effect of conditioning exercise on bone parameters at multiple sites in the radius and tibia of young Thoroughbred horses. METHODS The left and right radius and tibia were obtained from twelve horses, six of which had received conditioning exercise and six which formed the control group. Each bone was scanned at 5% intervals along its entire length using pQCT. RESULTS Bone strength, bone area and periosteal circumference were significantly greater for the group of conditioned horses in both the radius and tibia. Volumetric bone mineral density was lower while bone mineral content, endocortical circumference and polar moment of inertia were higher in the conditioned group of horses but the significance of these differences varied between the two bones. Cortical thickness was not significantly different between the groups in either bone. CONCLUSIONS Conditioning exercise stimulated a significant increase in the strength of both bones that could be attributed mainly to an increase in bone size, rather than differences in bone mineral content or density. The radius and tibia exhibited differences in the significance of changes in several bone parameters suggesting that not all bones respond in an identical fashion to imposed exercise.