Effects of equine racetrack surface type, depth, boundary area, and harrowing on dynamic surface properties measured using a track-testing device in a laboratory setting

The dynamic behaviour of racetrack surfaces during hoof impact is a likely risk factor for racehorse injuries and fatalities. A track-testing device that simulates equine hoof impact was used to assess the effects of surface type (dirt, synthetic), surface depth (2, 3, 4 layers), test boundary area (929, 6,606, 11,381 cm²), harrowing, and impact angle (0°, 20° from vertical) on dynamic surface properties. Surfaces were tested within a laboratory track-in-a-box. Surface type and depth, boundary area, and harrowing significantly affected dynamic surface properties during impacts (P < 0.05). The synthetic surface was generally less stiff, and had 26-73% lower maximum impact forces and load rates, than the dirt surface. Harrowing decreased stiffness and differences between dirt and synthetic properties. Measured surface stiffness was larger for the smallest depth and boundary area, but most surface properties were not significantly different between the larger boundary areas. Surfaces were less stiff with angled impacts than vertical impacts.