ARCHIVE - ARTICLES 2008

June 2008 - Biomechanics - surfaces and their effect on locomotion and shoeing

 

Archive - Forge Magazine - June 2008
Biomechanics - surfaces and their effect on locomotion and shoeing

by Kathy Carter

 

In the first of this series, we looked at how preventative techniques can help avoid equine injuries that can be attributed to imbalances of the feet, such as joint, tendon, and ligament stresses. One such technological example is Equinalysis biomechanical gait screening, which as farrier Haydn Price DipWCF has explained, can help farriers to shoe horses according to the animal’s individual conformation, level of training and the dynamic loading of the limb.

One simple benefit of biomechanical screening is the fact that both farrier and owner have a visual record of a how the horse moved on a particular day. This can be invaluable when the horse is responding to training, and the quality of his stride, as well as his strength and flexibility, are improving. However, the dynamic assessment of a horse, or lack thereof, is an area of concern for some owners, according to Haydn Price. “Farriery is by virtue of the equine, ‘dynamic’,” he says. “One over-riding complaint that regularly crops up from horse owners is, “my farrier just gets the horse out, and never even looks at him walking or trotting.” My question to farriers is, how can you be expected to initiate a continued treatment process in the form of a shoeing schedule, if you do not have a benchmark of assessment for the horse in question?”

Slowed down footage – of great benefit

Haydn’s is a pertinent question. The human eye operates at just 12 frames per second, where as cameras operate at 50 to 1,500 frames per second. So, while a visual assessment is better than no dynamic assessment at all, it is still limited in terms of the practical benefits of having a horse’s locomotion on video tape – for example, the ability to stop, rewind and play a particular stance or movement. According to farrier Martyn Elliott AWCF, being able to evaluate horses with video-based technology has been extremely beneficial to him professionally. “Without the ability to watch slowed-down movement of the horse, I could not even hope to see if there is a specific problem, or if I have any influence on the problem,” he states.
Farrier Mark Aikens DWCF agrees that dynamic assessment is key. “I believe it is important for farriers to observe the horse moving prior to shoeing, as more information can be gathered when assessing dynamic, as well as static balance,” he says. “Watching a horse walking and trotting from all angles allows us to assess the horse’s soundness and observe how each limb loads. But, when we assess a horse’s movement, our observations are subjective by their very nature; what we can see will differ to other people’s views, to a greater or lesser extent. With experience, our powers of observation will improve, but even the most perceptive onlooker will have limited accuracy, as two people will look at the same horse differently. Slow motion video footage permits farriers to be more informed about an individual horse’s dynamics, although of course it will still be an unquantified appraisal.”

The phases of equine dynamics

Haydn Price says that by videoing the horse in a straight line, farriers are able to more closely look at the two different phases of dynamics. “The ‘swing’ phase is generally dictated by conformation,” he states. “However, when we start to look at specific aspects, we may wish to alter the end of the swing phase, for example, the ‘point of contact,’ or the point at which the horse’s foot engages with the ground, to assume a more proactive output. This type of work is more prevalent when shoeing hind limbs. Alternatively, we may have to influence the point of which the foot leaves the ground – the breakover stage – that can have a major effect on joint angles within the swing phase.
“The second aspect of equine dynamics is the ‘stance’ phase, when the joints and limb begin to load with descending body weight,” Haydn continues. “As the horse moves forward, the weight increases through the lever arm. This aspect probably tells you the most, and is the one associated with lameness within the joints or soft tissue. This type of proactive, performance shoeing can really make a difference to a horse’s action and soundness, and can be honed considerably using video-based techniques.”

Biomechanical technologies

So, why isn’t the use of video footage more commonplace within farriery practise? “It is hard to estimate just how many farriers are familiar with biomechanical technologies,” muses Martyn Elliot. “I have spoken to some farriers who fully understand; some who understand but don’t really care; some who think they know, but don’t; and others who are completely clueless. One thing I will say is that it is very hard to be motivated when you are presented with a horse in a muddy gateway, or one that is trying to pull you from one side of the yard to the other.
“How the horse is presented to the farrier is key in terms of carrying out a shoeing session to the best of your ability,” Martyn continues. “When you are trying to assess the way a horse moves, it is imperative that you have a flat, level surface, and that the horse is compliant with being lead in a straight line at both walk and trot.
“The benefits to the farrier of being able to watch a horse before and after shoeing are tremendous; without watching the horse at least in walk, you might as well throw the shoes on from 10 paces, in my opinion. Every horse should be looked at prior to shoeing, whether it is a happy hacker, or a top class performance horse. It may be that some horses do not require any more than being observed walking too and from the stable, however, if you are trying to gain more performance out of a potential medal-winning dressage horse, it may require a more in-depth look. There is a form of biomechanical evaluation to suit every need and pocket.”

Arena characteristics

Excessive ground reaction force can affect the performance of all horses, from the leisure horse to the Olympic equine. Much work has been done in recent years to ascertain the affects of different surfaces on a horse’s soundness, from surveys aiming to establish whether arena characteristics and surface maintenance affect performance, to computer models that predict how surfaces ‘dampen’ the vibrations caused by hooves hitting the ground at speed. The Animal Health Trust has demonstrated that significant relationships exist between injury in dressage horses and particular features of surfaces on which horses regularly work, and experts agree that dressage horses are at particular risk of proximal suspensory desmitis (PSD), a widespread cause of injury to athletic horses and an increasingly common cited cause of ‘loss of use’ in insurance claims.
A poor arena surface can also easily result in long-term equine injuries; too-hard arena surfaces don’t absorb energy and can cause concussive injuries, while deep surfaces can cause strains. “I am increasingly concerned about the increase in equine PSD cases, and am very interested in the effects of surface characteristics on soundness,” says Haydn Price. “Fortunately, I am not relying on subjectivity to show me these effects – by simply filming a horse on a flat, hard surface and then again in a sand arena, it is possible to clearly see the compensatory work carried out by the horse’s limbs and joints once in the arena. For example, the hock may rotate excessively in a deep or soft sand arena as the foot lands and the loading phase of the limb begins; this can of course be physically detrimental to a horse being asked to perform high level movements. I am convinced that slowed-down video footage will be a very useful tool in the continued research into the causes of PSD.”