Modification of a force plate system for equine gait analysis on hard road surfaces: a technical note

Studies on horseshoe materials have been limited to the analysis of kinematic data to determine slip times and distances, since equine force plate analysis is traditionally undertaken on a rubber-surfaced force plate. The purpose of this study was to modify a force plate for measuring ground reaction forces on a road surface and report preliminary data from the system. A steel-reinforced concrete top plate of 18 mm thickness and mass 23 kg, and a 12 mm thick top plate of 6 mm bituminous macadam wear coat (road surface) contained in a tray constructed of 2 mm thick steel, mass 21 kg, were constructed. The top plates were bolted to a forceplate and resonance frequency of the force plate top plate combinations were 278 Hz (concrete) and 218 Hz (roadway), respectively. Simultaneous kinetic and kinematic data were collected while a horse, shod in steel horseshoes, was trotted over the concrete-topped force plate until 8 foot placements were recorded. The foot slipped for mean +/- s.d. 35 +/- 7 mm in 29 +/- 8 ms after impact and both Fy and Fz increased during foot slip. The ratio of Fy/Fz during slip was relatively constant at 0.56 +/- 0.05. The top plates have proved resilient in use and have withstood a variety of horseshoe designs and tungsten-capped stud nails with minimal damage. They enable measurement of ground reaction forces on hard surfaces and the calculation of the energy dissipated via foot slippage by integration of the craniocaudal force-foot position data after impact.