Movement symmetry and back range of motion in reining quarter horses

Back disorders and clinical lameness are often interrelated in equine athletes. To better diagnose and treat these conditions, it may be useful to investigate the relationship between thoraco-lumbo-sacral movement and movement symmetry, and to establish baseline values for thoraco-lumbo-sacral range of motion (ROM) in specific groups of horses. Using a nine-sensor inertial measurement unit system (EquiGait), we quantified differential rotational and translational thoraco-lumbo-sacral ROM and head and pelvic movement symmetry in twenty competitive reining Quarter Horses (AAEP lameness grade < 2/5) in walk and trot in-hand and during lunge exercise on hard and soft ground. General linear regression models were used to investigate the relationship between movement asymmetry parameters and thoraco-lumbo-sacral ROM. Along with establishing baseline thoraco-lumbo-sacral range of motion data for reining Quarter Horses, this study found that even subtle forelimb and hindlimb asymmetries have a significant effect on thoraco-lumbo-sacral range of motion. Increased movement asymmetry was associated with a decrease in thoraco-lumbo-sacral ROM, particularly for rotational movements. Specifically, forelimb asymmetry was linked to a decrease in flexion-extension and axial rotation in the sacral region and a decrease in flexion-extension in the cranial thoracic region. Hindlimb asymmetry was linked to a decrease in lateral bending in the lumbo-sacral region. Both forelimb and hindlimb asymmetry were consistently associated with increased lumbo-sacral dorsoventral ROM. Further studies should compare the baseline values for ‘normal’ horses established in this study with horses showing clinical evidence of ‘back pain’ and investigate different breeds and equestrian disciplines.