Breezing Thoroughbred Hoof Accelerations on Dirt and Synthetic Surfaces

Abstract

IntroductionRacetrack surface type has been shown to affect horse injury rates, limb kinematics, and ground reaction forces. Understanding hoof‐surface interactions may direct surface design to reduce the incidence of musculoskeletal injury. Hoof accelerations have been recorded at the trot on different surfaces. This study extends these analyses to racing gallop with quantified surface properties.MethodsLeft fore‐hoof accelerations (triaxial, ± 500 g, 1000 Hz) were collected during gallop (10–16 m/s, 5 Thoroughbred racehorses) on dirt and synthetic surfaces of known shear strengths (shear vane). Accelerometric vectors were filtered (5th order Butterworth, stance 85 Hz, swing 30 Hz). Peak accelerations and stance phase durations (limb preparation, hoof landing {heel‐strike and slide}, support, and grab) were compared using a mixed model analysis of covariance with surface, lead, stride frequency, and interaction fixed effects, and horse random effect.ResultsPeak dorsopalmar accelerations were 40% greater during landing on the synthetic surface (P = 0.06). Grab phase was 32% shorter on the synthetic surface (P = 0.02), with 34% less dorsopalmar impulse/mass (P<0.01). Previously reported failure shear stress of the synthetic surface was 20% greater, compared to dirt (normal stress >400 kN/m2, equivalent to trotting racehorse).ConclusionsDorsopalmar hoof accelerations were greater on the surface with greater shear strength (synthetic). The finding that accelerations were greater on the synthetic surface compared to dirt is in contrast to that of trotting horses on all‐weather waxed and crushed sand surfaces. This discrepancy may be due to differences in horse gait, but also large variability in surfaces. Consequently, it is important to quantify surface behaviors to understand the effect of surface design and maintenance on limb biomechanics and propensity for injury.Ethical Animal ResearchStudy protocols were approved by the University of California, Davis Institutional Animal Care and Use Committee and owner informed consent was obtained for all study horses. Sources of funding: Grayson Jockey Club Research Foundation Inc., Southern California Equine Foundation. Competing interests: none.