As in many other sports, e.g. gymnastics, judging dressage riding is problematic because the score is subjective. The aim of this study was to find a suitable method to support education of dressage judges and training of riders with a measurable criterion for riding harmony in the trot. We analysed the consistency of motion pattern 40 different rider–horse systems in trot (20 horses and 2 riders). A high-speed (120 Hz) 3D video system for motion analysis was used to track 20 markers taped to the horse and the rider. The angle between the line connecting the rider’s head to the rider’s back and that between the rider’s back to the horse’s head was calculated. Angular velocity and angular acceleration were derived. The lengths of the resulting vectors (LV) in the phase space were computed. Riding harmony was defined in terms of the average deviation of LV in the phase space.
The results of our study showed the professional rider–horse system had a significantly (P < 0.05) lower average deviation of LV (11.5% ± 1.4) than the recreational rider–horse system (13% ± 2.8). Thus, the professional rider–horse system had a motion pattern that was more consistent than the recreational rider–horse system and this was correlated to the average dressage scores, which were significantly (P < 0.001) higher for the professional rider (mean score ± SD, 7.3 ± 2.7) than those for the recreational rider (4.1 ± 3.0). As motion pattern consistency is one of the main characteristics of riding harmony, the results of these measurements can be used for education of dressage judges and riders.