Speed dependency of motion pattern consistency.

Treadmills are widely used in equine motion analysis. For the evaluation of the trot of a horse, a trotting speed with low variation between motion cycles is necessary to make the measurements reproducible. The aim of this study is to show how an individual 'optimum' trotting speed for lameness quantification can be determined. In this study, the stability of a horse's gait pattern was evaluated by calculating the standard deviation (S.D.) of motion-cycle speed (MCS). In trot, eighteen horses were analysed at several speeds. The measurements were taken with the ExpertVision System (Motion Analysis Corporation) every 3 km h(-1) (= 0.83 m s(-1)), from the lowest to the highest individual trotting speed. At the different speeds the S.D. of MCS and the asymmetry of the vertical head motion were compared. At the speed where standard deviation was minimum, motion asymmetry was maximum. In twelve horses this optimum speed was situated in the middle of the individual trotting speed range, and in six horses the optimum speed was the maximum speed. The method presented in this study allows the determination of an optimum trotting speed and so contributes to precision and consistency of equine lameness analysis.