Could Pressure Distribution Under Race-Exercise Saddles Affect Limb Kinematics and Lumbosacral Flexion in the Galloping Racehorse?

Back pain is frequently recognized 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 hypothesized that reducing pressures under saddles at thoracic (T) vertebrae 10-13 in galloping racehorses is associated with improved limb and lumbosacral kinematics. The objectives of the study were 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 and (2) compare limb and lumbosacral kinematics at gallop between 4 saddle types. Four Thoroughbred racehorses were galloped overground at standardized 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 ≤ .0001–.02). Saddle F had significantly lower peak pressures at T10-13, greater hip flexion, femur angle to vertical, and 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 the 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.