Effects of treadmill inclination on kinematics of the trot in Dutch Warmblood horses

To evaluate the effects of uphill trotting on stride characteristics, 6 well trained Dutch Warmblood horses trotted at 4 m/s on a horizontal and on an inclined (6%) treadmill. This was done under 3 different conditions, unloaded, mounted by an experienced 90 kg rider and loaded with 90 kg of lead, to study whether extra weight provoked more or different alterations than the incline per se. In all 3 test situations (unloaded, mounted and lead-loaded), heart rates were significantly higher on the inclined treadmill than on the horizontal treadmill. Stride duration tended to increase on the inclined treadmill. Stance duration increased significantly on a slope, more in the hindlimbs than in the forelimbs. In the unloaded condition, maximal fetlock extension of the forelimb decreased on the incline, whereas maximal fetlock extension of the hindlimb and tarsal range of motion increased significantly on the slope in all 3 conditions. The overall effect was that on an inclined treadmill the hindlimbs seemed to carry more weight (higher maximal fetlock extension), and to provide greater propulsion (higher tarsal flexion and increased pro/retraction).