Nineteen dressage horses were evaluated trotting in‐hand on a firm surface and ridden by their trainer in an arena with sand‐fiber footing at collected and extended trot. Data from inertial measurement units (IMU) on the head, withers, and pelvis measured maximal and minimal heights, ranges of data describing vertical motion, and
left‐right asymmetry under the three trotting conditions. IMUs on the cannon bones measured left right symmetry in limb pro/retractions.