The Effects of Training on Bone Fatigue and Failure by David Nunamaker, V.M.D., Jacques Jenny Professor of Orthopaedic Surgery Catastrophic fractures in Thoroughbred racehorses represent a significant problem for the entire racing industry. Epidemiological studies sponsored by the Grayson-Jockey Club Research Foundation have outlined risk factors for fatal injuries associated with training and shoeing practices. These studies are demonstrating fatigue failure of bone as being an important component of these catastrophic injuries.
Bone is a unique material.
The mineral phase imparts a brittle nature to bone and the organic phase imparts a plastic stretchable nature to the material. Therefore bone exhibits both of these characteristics. When bone is bent it is the organic phase which allows bending. If bone is loaded slowly, it will break at a lower load than if it was loaded quickly. Therefore the bone of the Thoroughbred racehorse can stand larger loads when the loads are applied quickly.