The effect of loading on the equine spine: a preliminary study

Although equine spinal motion has been analysed in vivo and in vitro, spinal pathophysiology and the mechanisms of injury are not well understood. Most horses are exercised mounted, yet the effect of a load on the spine is still unclear. The purpose of this study was to assess the effect of load placed on the spine on motion at the lumbosacral junction and the withers.

6 treadmill-trained Thoroughbreds were fitted with a saddle, hoof accelerometer and 2 MT9 inertial sensors (placed on the lumbosacral junction and withers), and spinal motion was analysed at walk (1.6 m/s) and trot (3.0 m/s) on a treadmill (condition 1). This was repeated whilst adding a load (2 sandbags, 30 kg, placed over the saddle) to the horse (condition 2). 3 of the 6 horses were re-tested a third time with the load removed again, this being identical to condition 1 (condition 3). The data were processed using Matlab™, and mean and standard deviation obtained and inferential statistics applied.

Spinal motion was significantly increased at the lumbosacral junction for mediolateral and pitch displacement at trot, and for roll displacement at the withers at trot when comparing condition 1 and 2. No significant changes were found when comparing all 3 test conditions. Loading of the equine spine altered motion in some movement directions at the lumbosacral junction and withers at trot, but not in any movement direction at the lumbosacral junction or withers during walk. Further studies combining spinal motion analysis and muscle function are required to enhance knowledge of the effects of a rider on equine spinal biomechanics.