Could pressure distribution under race-exercise saddles affect limb kinematics and lumbosacral flexion in the galloping racehorse?

Abstract Back pain is frequently recognised in racehorses, but saddle fit and design are rarely assessed. In sport-horses, relationships between horse-saddle interaction, back pain and altered kinematics are established, but few studies investigating horse-saddle interaction in racehorses exist. We hypothesised that reducing pressures under saddles at Thoracic (T)10-13 in galloping racehorses is associated with improved limb and lumbosacral kinematics. Objectives: To 1. determine pressure magnitude/distribution under 3 frequently-used race-exercise saddles and a saddle designed to reduce peak pressures at T10-13 on racehorses at gallop; 2. compare limb and lumbosacral kinematics at gallop between 4 saddle types. Four Thoroughbred racehorses were galloped overground at standardised speed wearing half tree, three-quarter tree, full tree race-exercise saddles (Saddles H/Q/T), and a saddle designed to reduce paraspinal pressure at T10-13 (Saddle F), in a cross-over design. Pressure distribution under saddles was recorded using a pressure-mat system, and gait features using high-speed-motion-capture. Results were compared between saddle types within horses. Maximum peak pressures at T10-13 occurred at trailing forelimb vertical, but pressure distribution varied significantly between saddle types. Peak pressures, femur-angle-to-vertical and hip-flexion angle were significantly different between saddle types (p≤0.0001-0.02). Saddle F had significantly lower peak pressures at T10-13, greater hip-flexion, femur-angle-to-vertical, forelimb and hindlimb protraction than Saddles H, Q and T. These findings suggest the femur has greater protraction in saddles with lower pressures at T10-13, indicating importance of race-exercise saddle design. Saddles with lower pressures at T10-13 could potentially allow increased range of spinal motion and altered muscle use, supporting improved hindlimb function.