When you buy a new horse trailer, chances are you’ll also get lots technical information about the “fatigue life” of mechanical parts like the shocks or the clamp to close the hitch. That fatigue life refers to how long these parts can be used—opening and closing, absorbing shock, clamping, or whatever they do—before they break.

Recently, researchers began studying a far more important fatigue life for horse owners: that of racehorse bones. Specifically, a team of Australian researchers looked at the subchondral bone—the bone lying under the cartilage at the joints—of racehorse legs to determine how well that bone stood up to repeated pressure.

“Every step a horse takes causes a tiny bit of damage to bones,” explained Sandra Martig, DrMedVet, PhD candidate and researcher at the Faculty of Veterinary Science at The University of Melbourne. “But nature knows about this, and the bones can repair the damage. That’s why in normal life people and horses don’t break their bones just from doing everyday things.”

However, intense training programs can get ahead of nature, Martig said. “Because horses in the wild don’t gallop as much as racehorses do, bones are not made for racing, and racehorses’ bones sometimes are unable to deal with the damage that accumulates during galloping,” she said. She estimates that as many as 80% of racehorses worldwide experience subchondral bone injury during their careers