MOTION PATTERN CONSISTENCY OF THE RIDER-HORSE SYSTEM
Keywords: riding, phase-space, trot, horse, kinematic, motion pattern
AbstractINTRODUCTION: Dressage riding is difficult to judge, because the aesthetics of the performance cannot be measured simply. The aim of this study was to show a method of visualizing and quantifying the harmony of the motion of a rider and a horse by evaluating their coordination. Rider and horse have a natural frequency when trotting; they can therefore be considered a system of coupled biological oscillators. The characteristics of such a system are determined by the innate and learned motion patterns, anatomy and physical condition of both participants. Any periodic motion can be described as a limit-cycleattractor in the phase space. The characteristics of an oscillator or a system of oscillators can be depicted as a phase plane diagram (PPD), which is a suitable method to visualize the characteristics (e.g., longterm behavior and limit-cycle) of a complex system, such as the ridden horse. METHODS: Twenty horses aged 4 to 22 years on different training levels were measured being ridden at trot by a professional rider and a hobby rider. The measurements were carried out from the right side, with six cameras (sample rate 120 Hz, resolution 240 x 833 points) tracing 20 reflecting spherical markers placed on the horse’s and rider’s right side. At least eight recordings of five seconds each were taken with the ExpertVision System of the Motion Analysis Corporation with the horse trotting on a 12 m long pressed sand track in an indoor riding arena. At least eight motion cycles of each rider-horse combination were analyzed. The 3-dimensional movements of the markers were used to deduce the angle between the linkages of rider’s head to rider’s back and of rider’s back to the horse’s head. Then the data were normalized to 100% of the length of the motion cycle. Angle velocity and angle acceleration were computed and from all three data-sets, scaled to 100% of the professional rider’s angle, angle velocity and angle acceleration; the trajectories in the phase-space were plotted and the lengths of the resulting vectors (LV) in the phase-space were computed. The mean and average deviation (variation of LV) of LV of every horse and rider were determined and grouped for each rider. The normal distribution of each group was tested with the Kolmogorov-Smirnov test. The Student test of paired samples and one-way analysis of variance were used to check the differences between the mean of the groups of LV and average deviation. RESULTS AND DISCUSSION: There was no significant difference in the mean of LV between the 2 riders, but there was a significant () difference in the average deviation of the LV, showing that the motion of the horse-professional rider system is more consistent than of the horse-hobby rider system. With this method the rhythm and the natural balance of the rider-horse system can be evaluated, and this information might prove a useful feedback for the education of riders.
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