Meeting Abstract

91.4  Friday, Jan. 7  Energetic cost of transitioning between trot and gallop and back in horses NAUWELAERTS, S.*; AERTS, P.; CLAYTON, H.M.; University of Antwerp/Michigan State University sandran@ua.ac.be

In their classic 1981 study, Hoyt and Taylor suggest that gait transitions in horses occur to reduce the metabolic cost of locomotion at a given speed. This view has been challenged by more recent research proposing that a reduction in forces is the mechanical cue to switch gaits. Most of the previous research was performed on animals running on treadmills or both compared gaits were at steady state. The aim of this study is to unravel the mechanics of the transition itself. In this study, we performed a full kinematic analysis of 5 miniature horses transitioning over ground using a Motion Analysis System consisting of 8 infrared cameras. We aimed at having five strides (two before and two after the transition) at a steady acceleration. Thirty-six reflective markers were attached at the joint centers of each body segment. Footfall patterns were obtained, joint and segment angles were calculated and mechanical energy calculations (kinetic, potential, rotational) were performed. We hypothesize that the kinematic changes will show up in the proximal joints rather than the distal ones (traditionally described as “passive”), and that the mechanical energy will show a peak at the transition. Since the horses accelerate at a constant acceleration, the difference in intercept between the regression lines through the mechanical energy calculations plotted against speed, will determine the cost of transitioning. We will also test the hypothesis that the cost of down transition is higher than the up transition.