The forces exerted by a rider on a horse have a direct influence on the mechanical load experienced by the horse and consequently on its motion pattern. The aim of this thesis is to explore the biomechanical interaction between rider, saddle and horse in order to get insight in the loading of the horse and to identify potential opportunities to reduce load-related injuries.
The influence of man on the horse is mediated trough tack, which functions as an interface between the horse and the human being(s) using it. The tack is often connected to both horse and rider and is therefore well-positioned to incorporate measuring devices that can record the forces between horse and rider.
So-called saddle-pressure measuring devices have been used to evaluate saddle-fit and could also be a useful tool to study the interaction between horse and rider. However, not much was known thus far about the validity, reliability and usability of these devices for this purpose. Therefore, the first studies in this thesis focussed on this topic. The FSA system was only reliable in highly standardised circumstances. The Pliance system provided reliable and repeatable results and can be used indeed to study the interaction between horse and rider. In this thesis it was used to evaluate the effect of rider position on the force distribution beneath the saddle and to study the signals given by the rider to the horse performing lateral movements in dressage.
One of the important physical properties of the rider that influences the horse is the rider’s weight. The effect of tack and weight on the movements of the horse was therefore studied. The introduction of a mass with considerable weight on the horse’s back induced an overall extension that might contribute to back injuries.
During trot, the rider can either rise from the saddle during every stride (rising trot), or remain seated (sitting trot). The back movement during rising trot showed characteristics of both sitting trot and the unloaded condition, with a higher degree of extension during the sitting phase and less extension in the standing phase. In the standing phase peak force on the stirrups is higher, but the overall vertical peak force on the back of the horse is less. This supports the general assumption that rising trot is less demanding for the horse than sitting trot.
Three spring-(damper-)mass models were constructed to evaluate the biomechanical requirements the rider has to comply with during sitting trot, when using the modern riding technique adopted by jockeys during racing, and in rising trot. The models demonstrate which combinations of rider mass, spring stiffness and damping coefficient will result in these riding modes. Optimization to minimize the peak force of the rider and to minimize the work of the horse resulted in an “extreme” modern jockey technique, which is not adopted by actual riders. The incorporation of an active spring system for the leg of the rider, was needed to simulate the rising trot.
The general discussion argues that the simultaneous use of a variety of approaches is required to further our understanding of the interaction between horse and rider. A combination of experimental research, which makes use of cutting-edge techniques to measure kinematics of horse and rider, forces acting between horse and rider and between horse and environment, and muscle activation patterns of both horse and rider, with mathematical modelling is the way forward. This combined approach could answer questions concerning the external and internal biomechanical loading of horse and rider of several horse riding and training techniques. Techniques that minimize risk of injury of both horse and rider could possibly be identified, reducing welfare problems of the equine athlete.