Surface variable effects on the dynamic properties of thoroughbred horse racetracks

Historically, equine racing surfaces have been selected and maintained without considering quantifiable data for horse biomechanics or surface mechanical properties. This approach is currently shifting in the racing industry, with an increased interest in understanding the mechanics of the hoof-surface interface to reduce injuries. This dissertation examines three components influencing the hoof-surface interface: 1) correlations between mineralogical composition of dirt tracks, track designs, and climate; 2) the effect of variable cushion depth on dynamic loading, and 3) the effects of different horseshoes on dynamic loading. The second and third pieces of this research are based on an experimental procedure designed to mimic in-situ performance.;In dirt racetracks, clay content is critical to moisture management and influences mechanical properties. Clay mineralogy was determined for 26 tracks representing three track designs: shallow sand, false base, and false base with a pad. Results demonstrate that shallow sand tracks occur in areas with the highest annual precipitation and have the lowest average clay content, whereas tracks with a false base and pad have the lowest annual precipitation and the highest average clay content. Understanding moisture and clay effects in racetracks can aid in quantifying track maintenance decisions.;The next tested parameter was the effect of cushion depth on dynamic loading experienced by the horse for a range of surface conditions. The difference of 5 cm in depth significantly affects the peak load and loading rate. This effect may be reduced when a surface material is maintained at a moisture level at which maximum dry density occurs.;Finally, three horseshoes--a flat racing plate, a serrated V-grip, and a shoe with a grab and heel calks--were tested on synthetic and dirt track materials. The shoes were not significantly different barring one exception: loading rate for the V-Grip shoe on a synthetic surface was significantly less than that of the other shoes. All other statistically significant differences were due to surface variation rather than shoe type.;Understanding these variables adds to the body of knowledge needed for more quantitative decision-making on racing surfaces and also adds to the data framework necessary for robust epidemiological studies.