University of California Davis released new research in the journal Scientific Reports exploring the relationship between training and bone health in racehorses in the US. The study reports that high-speed and intensity exercise may be associated with more damage and reduced robustness in injured lower leg bones in racehorses.

Among the findings, UC Davis’s Sarah Shaffer and her colleagues explored the relationship between exercise and bone damage, while examining the proximal sesamoid bone (a bone in the lower leg) during the necropsy of 20 racehorses. The authors examined the fractured and intact proximal sesamoid bones from 10 horses who had suffered fatal fractures. They compared the bone mineral density, bone volume, and microdamage in this sample to intact proximal sesamoid bones of 10 control horses. Case horses had a bone lesion with high levels of microdamage and low bone volume. These observations were used to estimate the rate of remodeling occurring in the sesamoid bones.

The authors also modeled the relationship between bone damage and remodeling, and exercise intensity, time off from exercise (layups), and exercise levels between two and 10 months before the racehorse died. For injured horses, damage at the lesion site was associated with high-speed workouts in the four months prior to death, as well as greater time between races while the horse was in active training. Frequent high-speed exercise before death was also associated with lower bone density at the lesion site. However, at other locations, higher rates of remodeling were associated with more cumulative races in the 10 months prior to death.