Phases of the stance
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Two research projects that contribute new knowledge into the interaction between the equine hoof and the ground were presented at the 15th International Equitation Science Conference, hosted by the University of Guelph.

The findings are part of an ongoing and massive collection of data by the laboratory of Dr Jeff Thomason at the Ontario Veterinary College (OVC), which is taking a detailed look at the interaction of the hoof with the ground, including the shock and forces acting on the horse’s leg on a wide variety of surfaces and conditions, in racing and other sport horse disciplines.

Dr Thomason has been measuring joint loading since 1985 when he put his first strain gauges on a hoof. Each of the following two studies add to the growing body of knowledge, which ultimately serves to optimize surfaces in order to reduce sports injuries.

Effects of surface and horse size on hoof loading

Ontario Veterinary College student, Alexis Szpakowski presented the preliminary findings on the interaction between body size and surface type on hoof loading to a packed audience at the University of Guelph’s Rozanski Centre on Tuesday 20th August 2019.

Szpakowski’s study included ten horses of varying breed and ranging in size from approximately 356 kg to 673 kg.  The horses were fitted with three strain gauges and an accelerometer, which were glued to both front hooves to measure the strain, as a surrogate of force, and acceleration experienced by the hoof while the horse is in motion.

The same rider piloted each horse at a trot on two surfaces:

  1. an indoor arena with firm sand mix,
  2. a soft sand outdoor ring.

Loading measurements were recorded from impact, slide, and midstance for a minimum of 10 stances. The stance phase is the phase during which the hoof remains in contact with the ground as depicted in the infographic.

When comparing the two surfaces, preliminary results revealed the loading measurements for impact, slide and force at midstance were all lower for the soft sand ring by 10 – 60%.

When horse size was added to the results, slide values were not affected, however, the impact accelerations decreased in the firmer sand mix (indoor arena) but not in the softer sand (outdoor ring). Midstance loading increased as the size/weight of the horse increased in the soft sand outdoors but not on the firmer surface indoors.

This result surprised the researchers and suggests that larger animals experience higher loading at the midstance on the softer surface and lower on the firmer surface. While there is a lot more to study in this area, this preliminary data contributes to the ongoing research being undertaken at Dr Thomason’s laboratory and elsewhere about the way horses’ limbs interact with the surfaces they train on.

“Footing is very important simply because the characteristics of each surface directly affect the loading of the hoof,” says Szpakowski, “I loved the hands-on aspect of data collection in this study and how even preliminary results, such as mine, can contribute to a growing body of knowledge to improve equine health and help reduce injuries related to footing including lameness and limb fractures.”

Asymmetrical limb loading in Thoroughbred racehorses as a possible cause for injury

Ontario Veterinary College graduate student, Danielle Halucha presented findings from a second study titled ‘Asymmetrical limb loading in thoroughbred racehorses as a possible cause for injury’ at the 15th International Society for Equitation Science conference.

Working under Dr Thomason’s direction, Halucha’s study set out to quantify mechanical changes in loading comparing both forefeet of Thoroughbred racehorses among various locomotory conditions that are normal for training and racing:

  • speed,
  • lead (left lead or right lead), and
  • curve (turn or straight).

The research aim was to identify changes within locomotory condition that are sufficiently large to be implicated in the causation of injuries for which these conditions are known risk factors.

In this study, comparing loading of the forelegs, Halucha explained, “Mid-stance stood out as having the greatest average percentage change for both means and variances compared to other phases of the horses stride.”

The stance phase – when the hoof is on the ground – is subdivided into four phases:

  1. primary impact,
  2. secondary impact,
  3. midstance, and
  4. breakover.

During each of this sub-phases, the hoof experiences different forces and accelerations. Each of them is associated with a risk factor for injury; however, it has been difficult to identify a mechanical cause of injury.

For this research, Thomason’s team attached hoof sensors and accelerometers, to record over 30 measurements per footfall; all of which tell of the shock, loading and timing.

This particular study looked at risk factors for injury and loading of the hoof under different conditions. These conditions were chosen from the Equine Injury Database and current epidemiologic studies conducted on North American racehorses.

“There are many risk factors for injury in North American racing that have already been documented through various epidemiologic studies,” says Halucha.

“Some of these include the age of the horse, experience and the racing surface. However, the underlying mechanical causes of injuries are not well understood.

“In order to minimize the risk of mechanical injuries, we must understand what, in regards to mechanical loading, is changing or going wrong.”

In this study, the researchers were able to note significant differences in the variances, raising the possibility that some degree of unpredictability in loading should be further investigated when addressing the causes of injury.

“I would love to go back and examine the outliers and potential outliers more closely and see what information they might hold,” says Halucha.

“With regards to biomechanics research in general, I think that by continuing to dissect the complexities of loading and what can affect it, we are getting closer to the potential mechanical causes of injury.”

(In statistics, an outlier is a data point that differs significantly from other observations. Outlier points can indicate faulty data, erroneous procedures, or areas where a certain theory might not be valid and are, therefore, usually excluded from the data set.)

The commonly held idea that the horse ‘took a bad step’ suggests that the variability and the outliers in the data set collected might provide more information than the magnitude of loading or mean changes in loading when identifying risk factors for injury.

Find more related news at EquineGuelph.ca

From the Ground Up – 10 years of exploring surfaces
Racing Surfaces White Paper
Health Studies with an Impact – Reducing Catastrophic Racing Injuries

Save the date for the 16th International Society for Equitation Science Conference – August 11-14, 2020 at Hartpury University, United Kingdom
with the theme: “Succeed with science: performance, practice and positive wellbeing”

This article was edited from materials distributed by the International Society for Equitation Science (ISES) a not-for-profit organisation that aims to facilitate research into the training of horses to enhance horse welfare and improve the horse-rider relationship.

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