Leading the Way in Equine Research

Equine Biomechanics

Dr. Sue Stover has conducted several studies looking at different surface areas that equine athletes compete on and how they impact the biomechanics of the horse. 

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Dr. Symons Honored with Wilson Award

Dr. Jen Symons received the 2018 James M. Wilson Award in recognition of her contributions to equine research. As a mechanical and biomedical engineer, she collaborated with Dr. Sue Stover and other researchers on the study ‘Modelling the effect of race surface and racehorse limb parameters on in silico fetlock motion and propensity for injury.’

At the time of the study, she was part of the Biomedical Engineering Graduate Group at UC Davis. She is now an assistant professor of mechanical and biomedical engineering at the Shiley School of Engineering at the University of Portland. She explains her role in this project as follows:

Previous studies have measured galloping horses on different race surfaces. However, the relationship between race surfaces and racehorse limb motions is complex involving many factors within the horse and race surface, like tendon stiffness and race surface depth. The aim of this study was to consider the effect of changing factors on fetlock motion during gallop, and to determine which factors produce the greatest changes.

We used a computer model of a virtual racehorse galloping on a virtual race surface that has produced consistent limb motions with those measured from actual galloping racehorses on measured race surfaces. This computer model is an economical tool that allows us to gain knowledge of many different factors related to race surfaces and racehorses, without subjecting any animals to research protocols.

Study results indicate that the depth of the upper, softer layer of the race surface has the greatest potential to influence fetlock flexion. Increasing the depth of this layer within the model decreased the degree of simulated fetlock flexion during gallop. Practically, this parameter is related to race surface maintenance, specifically depth of harrowing. Other parameters that produced lesser changes in fetlock motion included lower layer race surface mechanics and racehorse tendon/ligament stiffness. Changes in friction between the hoof and race surface produced the smallest changes in fetlock motion.

These computer model results provide evidence to guide race surface management decisions to reduce the incidence of fetlock injuries in racehorses, particularly through the depth of harrowing race surfaces.

Thanks to generous donors, the Center for Equine Health has been able to fund research that advances equine veterinary medicine over the past 45 years. Dr. Sue Stover, professor of veterinary anatomy and director of the J.D. Wheat Veterinary Orthopedic Research Laboratory, has conducted a variety of studies that improve racing safety and provide insight into how different surface areas of tracks and arenas impact equine athletes.

After completing extensive work evaluating the effect of race surface on injuries in Thoroughbred racehorses, Dr. Stover began in investigate the effect of arena surface on fetlock motion in jumping horses. Injuries to structures that support the fetlock, pastern, and hoof (suspensory ligament, superficial and deep digital flexor tendons) are the primary causes of performance limitations in show jumpers. The likelihood of injury to these areas increases with high limb loads and greater fetlock extension. Characteristics of the arena surface affect maximum limb loads, and thus the risk for injury.

The project studied both dirt and synthetic arena surfaces with the approach that a less stiff, more compliant arena surface, with sufficient strength to support the hoof, could result in lower limb loads and lesser fetlock joint hyperextension, and thus have a lower likelihood of inducing common injuries.

Investigators found that the dirt arena surface was stiffer and had higher vertical impact loads than the synthetic surface. Therefore, the dirt arena had more resistance to deformation of the hoof into the surface. However, the synthetic arena surface had higher cohesion (i.e. resistance to horizontal motion or slide of the hoof). During take-off for the jump, fetlock extension and hoof movement were greater on the synthetic arena than the dirt arena surface. During landing, fetlock extension was greater and the toe of the hoof penetrated further into the synthetic arena than the dirt arena surface.

Because extreme fetlock and hoof motions increase the risk for injury, arena surface design and management have the potential to prevent injuries in show jumping horses. However, further work is needed to determine the optimum arena surface design and management for injury prevention.

This study and the summary for many others can be found online in the 2018 CEH Research Review.