Reasons for performing study
The effect of racetrack surface (dirt or synthetic) on distal hindlimb kinematics of racehorses running at competition speeds is not known.
Objectives
To compare distal hindlimb and hoof kinematics during stance of breezing (unrestrained gallop) racehorses between dirt and synthetic surfaces.
Study design
Two-dimensional kinematic video analysis of 5 Thoroughbred racehorses galloping at high speeds (12–17 m/s) on a dirt racetrack and a synthetic racetrack.
Methods
The positions of kinematic markers applied to the left hindlimb were recorded at 500 Hz. Position, velocity and acceleration of joint angles and hoof translation during stance were calculated in the sagittal plane. Peak translational and angular kinematic values were compared between the dirt and synthetic race surfaces using mixed model analyses of covariance.
Results
Maximum and heel-strike metatarsophalangeal (fetlock) angles were greater (P<0.05) on the dirt surface than on the synthetic surface. Maximum fetlock angle occurred earlier during stance on the dirt surface (P<0.05). Greater horizontal displacement of the heel during slide occurred on the dirt surface (P<0.05).
Conclusions
During high-speed gallop, hindlimb fetlock hyperextension and horizontal hoof slide are greater on a dirt surface than on a synthetic surface. Synthetic race surfaces may mitigate risk of injury to hindlimb fetlock structures by reducing fetlock hyperextension and associated strains in fetlock support structures. Differences in hoof slide may contribute to different distal hindlimb kinematics between surfaces.
