In-Situ Strain Measurement on the Equine Hoof

摘要

The mechanical interaction between hoof and track with every footfall during training and racing has many potential effects on the occurrence of injury and lameness in racing Thoroughbred horses. The purpose of this study was to use the hoof as a strain and acceleration transducer to characterize aspects of this interaction on natural (turf) and artificial surfaces. A triaxial piezoelectric accelerometer and 45° rosette strain gauge were attached to the right forehoof of each of 11 race-trained Thoroughbred horses. Our prediction was that surface would affect impact accelerations, but not strains. At the midpoint of the stance at constant velocity, the principal compressive strain is proportional to vertical force and impulse, which should be independent of surface. Recordings were made as the horses galloped over 200-m long straightaways on each surface in random order, and within 20 minutes. All trials were at the same nominal velocity of 10 m/s, with the same rider, and were sampled at 14 KHz per channel. Ambient temperatures were 18-20°C. Mean peak deceleration perpendicular to the hoof wall impact was 1074±412.5 m/s~2 on turf and 648±329.2 m/s~2 on the artificial surface, significantly lower (p<0.05). For every horse the acceleration on turf was higher. Mean principal compressive strain at mid-stance on turf was -2269±1049.1με, and on the artificial surface was -1932±593.3με. The difference was not significant (p>0.05), but every horse showed slightly higher strains on the turf. Thus, the artificial surface reduced impacts on the hooves of most horses compared with natural turf, while having no significant effect on strains. At least one caveat applies to interpretation of the data: They were recorded under a narrow ambient temperature range, and it is not known how temperature affects the properties of the sand-polymer mix that largely comprises the artificial surface.