The study team identified four factors associated with particularly high odds of injury in this population of racehorses:
- First-born Two-year-old Thoroughbred (who were the first-born of mares) were found to be at increased risk, particularly for shin soreness, which is more formally known as dorsal metacarpal disease;
- Two-year-old horses who had a total preparation length of between 10 and 14 weeks;
- Thoroughbreds of all ages that ran a total distance of 2.4 to 3.8km (12–19 furlongs) at a fast gallop (faster than 15 m/s; 13 s/furlong; 900 m/min; 55 km/h) in the four weeks preceding injury; and
- Horses three years and older that ran 3.0 to 4.8km (15–24 furlongs) at three-quarter pace and above (faster than 13 m/s; 15 s/furlong; 800 m/min; 48 km/h).
“We recommend that these horses should be monitored closely for impending signs of injury,” the study team said.
Increasing total preparation length was linked to higher odds of injury in horses of all ages, but particularly in two-year-old horses. An increasing number of days exercised at a slow pace decreased the odds of injury in horses of all ages.
“This is consistent with other reports and our understanding of response to exercise, as the magnitude of the forces and strains generated during slow work are less likely to result in tissue failure than those forces experienced during high-speed exercise. “Increasing the number of days worked at a slow pace may be more effective for preventing injury, if horses are perceived at a higher risk, than resting the horse altogether,” they said.
Two-year-old horses are likely more at risk of injury as total preparation length increases because they need the rest period to enable their tissues to repair and adapt to the effects of race training, the authors said. “In contrast, tissue adaptation has already occurred in older horses and they can withstand longer periods in race training.”