Epsilon Open Archive

Abstract

This thesis is a study of the hoof deceleration and the propagation of impact related shock waves through the structures of the distal limb in the beginning of the stance phase. The equine limb has an in-built shock absorbing capacity, with an anatomy that gives a successive disto-proximal loading that prolongs the time of loading uptake. The repetitive impulsive loading subjected to the limb following each hoof impact has been suggested to be an important factor in the mechanical stress that if sufficiently repeated may lead to subchondral bone damage. The horses used in the study were Standardbred trotters. The deceleration pattern of fore- and hind hooves were recorded with accelerometers at different circumstances. In the first study, horses trotted at slow speed over a force plate. One accelerometer glued to the hoof wall, and one fixed to the third metacarpal bone, in order to record the transmission of impact transients. The initial impact peak was assumed to be negligible proximal to the fetlock joint. The length of the hoof braking seemed to influence on the attenuation of the following peak decelerations. In the following studies only hoof mounted accelerometers were used. In the second study the deceleration patterns of the fore- and hind hooves were compared over the force plate on a sand surface at slow trot. In the third study the hoof deceleration was compared between two different surfaces. The forth study was a field study on the hoof decelerations at different speeds (4.7-12.7 ms-1) on a training race track. The hoof deceleration is suggested to be divided into two parts. The first is characterized by large impact peak that is mainly attenuated distal to the fetlock joint. The second part is characterized by the onset of loading of the fetlock joint and the following rapid movements of distal bone segments, and the interaction between the ground surface and the hoof. The loading rate and the magnitude of the horizontal peak decelerations increase with speed and with a higher friction between the ground and hoof. The results improve the knowledge of the shock absorbing capacity of the equine limb and the mechanisms behind indicators of mechanical stress to the limb.