trong>Narrator: This is Science Today. Stress fractures in racehorses can result in fatal injuries. In fact, the most recent figures available show that in 2004, 81 percent of fatal injuries in racehorses were caused by muscle and bone problems. Dr. Susan Stover, a horse anatomy expert at the University of California , Davis says that stress fractures are the accumulation of microscopic damage suffered during training and racing.

Stover: In most instances these factures we think are the result of the pre-existing injury that creates a local weakness in the bone so that the bone gives away under otherwise normal racing and training circumstances.

Narrator: Stover recommends that the racehorse industry reassess the training regimen and racing schedules.

Stover: Horses that are trained more intensely are at a higher risk for catastrophic injury. If we can work with training schedules to prevent these injuries we can probably make a big impact on the welfare of horses in training and racing.

Narrator: For Science Today, I'm Larissa Branin.