Treadmill study of the range of back movement at the walk in horses without back pain.

Abstract

To evaluate back movement during walking in horses. 22 adult horses with no history or signs of back pain. 3-dimensional movements of markers on the hooves, head, and back were measured with a motion analysis system while the horses were walking on a treadmill. The positions of markers on the hooves, head, and the skin above the spinous processes of T5, T10, T16, L3, and 2 sacral vertebrae were recorded. From a minimum of 6 walking motion cycles/horse, marker movement and the time of occurrence of minimum and maximum marker positions within the motion cycle were determined. Angles were calculated between the markers on the head, T16, and S4 or S5 and between the markers on T5, T16, and S4 or S5. Lateral back movement was maximal at L3, where it reached (mean +/- SD) 3.5 +/- 0.8% of the horses' height at the withers. Maximum dorsoventral back movement was found at the sacrum, where it reached 4.7 +/- 1.3% of the height at the withers. In the horizontal plane, the angle between T5, T16, and S4 or S5 was altered by 11 +/- 2.5 degrees during the motion cycle. In the sagittal plane, the angle between the head, T16, and S4 or S5 was altered by 7 +/- 3 degrees. Results of this study may be used as basic kinematic reference data for evaluation of back movement in horses.