Saddle fit is an important part of a horse’s performance and health as an ill-fitting saddle can decrease performance and lead to injury. Dr. Russell Mackechnie-Guire indicated in The Horse that there is a notion in the horse industry that fitting saddles too wide will allow the thoracolumbar region of the horse to increase its range of motion and improve muscular function. However, there is no science to support this opinion. The thoracolumbar, or t-l, area is from the withers to the pelvis where the saddle fits.
A research team tested different saddle fits that were correct, narrow and wide on the movement of horses. The team fitted 13 sound horses with a validated sensor system and glued inertial measuring units along each horse’s poll, withers, middle of the back, lower back and hips. All horses were ridden by two similar-sized right-handed female riders using a general-purpose Kent and masters English saddle because the tree width is adjustable. The saddles were fitted correctly, narrow and wide by five master qualified saddle fitters and the differences in tree widths were 10% increase or decrease. The horses were warmed up and cantered on both reins and were ridden on a calibrated track. Results indicated horses wearing the wide saddle tree had significantly less flexion and extension of the middle of the back compared to the correct width tree. Horses wearing the wide saddle tree had more axial rotation at the withers but less axial rotation at the middle of the back and at the lower back where axial rotation is rotation around the horse’s spine. Also, the narrow tree saddle reduced lateral bending at the middle of the back so width of the tree does make a difference, and increasing the width may not be good for all horses.