The effect of a saddle on the kinematics of the thoracolumbosacral spine at walk and trot in-hand

There have been significant advances in research investigating horse-saddle-rider interactions. However, evidence on the effect of a saddle without rider on the horses’ spinal kinematics is limited. This study aimed to quantify the thoracolumbosacral kinematics with and without a saddle at walk and trot in-hand. Thoracolumbosacral kinematics of eight horses (10±4 years, 1.68±0.05 m) were quantified using eight inertial sensors (4.7×3.0×1.1 cm) placed on the head, T5, T13, T18, L3, TS, left/ right tuber coxae. Data were collected walking and trotting in-hand on a hard surface with/ without saddle. Saddle and girth fit were checked subjectively by qualified saddle fitters. Translational, rotational, and differential rotational ranges of motion (ROM) for each condition were analysed using paired t-tests. Stride time did not differ between conditions (P>0.05). At walk, T13 and T18-L3 yaw increased by 21% and 21% respectively and sacrum pitch by 4% in the saddle trials compared to the trials without, whilst T5 roll decreased by 18% and T5-T13 yaw by 22% (all P≤0.05). At trot, T13 pitch, T13-T18 and T18-L3 yaw increased by 20, 77, and 27% respectively in the saddle trials compared to the trials without, whilst T5 dorsoventral flexion, laterolateral flexion, and roll decreased by 5, 17, and 21% respectively (all P≤0.05). These findings suggest that a saddle without rider alters the horse’s spinal kinematics at walk and trot in-hand, with an increased ROM in caudal thoracolumbosacral segments and decreased ROM in cranial thoracic segments. It is emphasised that the saddle plays a significant role in the horse-saddle interaction.