Asymmetries of horses walking and trotting on treadmill with and without rider

Abstract

Background: Left-right movement symmetry is a highly desirable characteristic in sport horses. Objectives: This study compared movement symmetry in well-trained dressage horses in unridden and unrestrained position and ridden in a dressage frame, and investigated possible associations between gaits. Study design: Experimental study. Methods: Seven sound, high-level dressage horses were measured at walk and sitting trot on a treadmill at several speeds under two conditions: with and without rider. Left-right differences in stance duration, stance protraction and retraction based on longitudinal hoof positions, ipsilateral limb tracking, minimum and maximum vertical positions of the dorsal spinous processes of the sixth thoracic (T6), third sacral vertebrae (S3) and wing of atlas, and vertical ground reaction forces were calculated and analysed in mixed models. Results: At walk, five body variables indicated increased asymmetry in the ridden condition compared with unridden condition: forelimb stance duration (unridden/ridden left-right differences 9 vs 13 ms; P =.008), forelimb stance protraction (P =.004), stance retraction (P =.001) and first force peak (P =.003), and hindlimb stance retraction (P =.01). At trot, six body variables were more asymmetrical in the ridden condition: forelimb stance duration (2.5 vs 3.8 ms, P =.004); hindlimb stance protraction (P