A biomechanical analysis of relationship between the head and neck position, vertebral column and limbs in the horse at walk and trot

摘要

Back pain is a common problem, and one contributing factor may be the training method used. The head and neck position plays an important role in the training of horses. However, how different positions affect the back and limb kinematics of the horse is not well described scientifically. It is important to understand how the rider affects the kinematics of the horse during training in order to prevent injury and also to facilitate rehabilitation of a horse with lameness or back dysfunction. The purpose of this thesis was to evaluate the effect of different head and neck positions on the kinematics of the back and limbs of the horse. The horses used in the present studies were privately owned riding horses competing at different levels. The measurements were done with skin-fixed markers and high speed cameras. The markers were placed on the head, neck, back and limbs of the horse. Cameras were positioned around a treadmill and in study III and IV the treadmill was instrumented with a force measuring system. In study I-II, the horses walked and trotted on the treadmill with three different head and neck positions achieved with side and long reins respectively. In study III and IV six positions were evaluated with and without rider. The head and neck position influenced the back and limb kinematics significantly of the horse, especially at walk. The range of flexion-extension movement of the back and the stride length decreased when the neck was restrained in the high position. Even a low position restricted the movement of the back. The different head and neck positions also affected the curvature of the back. With a raised position of the neck the cranial part of the spine was extended while a low position caused a flexion of the spine. The unrestrained horse seems to rely more on the forelimbs for vertical support and use the hind limbs in a more horizontal direction. At walk the stride length and the movement of the pelvis increased, which can be useful for training purposes, while at trot the gait economy is likely improved with a free head and neck position. Extreme elevation of the head and neck caused the most dramatic kinematic changes. Working the horse in this position for a long period of time or at high intensity may therefore lead to transition from training effect to injury. Intervention on the head and neck position can markedly affect the movement pattern at walk, even if the rider’s hand is light enough to allow the horse a normal range of neck movement. At trot the movement pattern is less sensitive to differences in the position at which the head and neck is restrained, as long as not extreme, but the movements differ clearly between restrained positions and free position. The head and neck position also affected the limb kinematics, weight distribution between fore- and hind limbs and thereby the ground reaction forces.