Meeting Abstract

P3.193  Sunday, Jan. 6  Ground reaction forces during transition from trot to canter NAUWELAERTS, S.*; AERTS, P.; CLAYTON, H.M.; University of Antwerp, Belgium sandra.nauwelaerts@ua.ac.be

Gaits are defined based upon specific inter-limb coordination patterns characteristic to a limited range of speeds and of which one or more defining variables change discontinuously at a transition. With changing speed, horses perform a repertoire of gaits, walk, trot, canter and gallop, with transitions between gaits. The underlying mechanics involving such transitions are still unclear. In a previous study on the kinematics of the transition from trot to canter in miniature horses, early and short placement of the forelimb that becomes the leading limb in the canter was observed due to a shortened swing phase prior to the stride where the first phase shift (dissociation) away from the trotting pattern occurs. Based on this observation, we proposed that the transition was initiated by the fore limb perturbing the cyclical patterns of the trot resulting in a cascade of dynamic changes designed to restore the dynamic stability of the system. We expect the dynamic changes to become apparent by a change in the loading of the leading forelimb in the transition stride. To test this hypothesis, we measured joint kinematics and ground reaction forces of the forelimbs of four miniature horses transitioning from trot to canter. Twenty-four trials were recorded using a ten camera MotionAnalysis camera system and four Bertec force plates. Peak force, impulse and force rate at impact were measured for each hoof at each stride in the trial. Stride zero was defined as the stride, starting with contact of the leading forelimb and included the first dissociation in the swing phase of the dissociating diagonal limb pair. Vertical ground reaction forces under the leading, dissociating fore limb were lower in stride zero compared to the other strides, but horizontal forces did not change. The change in force magnitude and orientation will be coupled with kinematics and implications for motor control will be discussed.