Biomechanical responses of the back of riding horses to water treadmill exercise.

There is a lack of evidence for the presumed beneficial effects of water treadmills on the movement of the horse's back. The aim of the study was to evaluate the effects of water treadmill exercise on axial rotation (AR), lateral bending (LB) and pelvic flexion (PF) in horses. The back kinematics of a group of riding horses were studied at the walk in a water treadmill at different depths of water (hoof, fetlock, carpus, elbow and shoulder joint levels) over a period of 10 days. Skin markers were placed at anatomical locations on the back. AR, LB and PF were measured on days 1 and 10 using two high-speed video cameras. There was a significant increase in AR compared to baseline at the level of the carpus and at higher water levels, whereas LB was significantly lower than baseline values at water levels that reached the elbow and shoulder joints. PF was significantly higher than baseline values at each water depth other than hoof water depth. At increasing water depths, there were significant increases in flexion and rotation of the back. At the highest water levels, there was reduced bending of the back. After 10 days, horses exhibited more bending of the back.