48 TheHorse.com THE HORSE July 2012

STEP BY STEP

In Joe Johnston’s Hollywood depic-tion of Hildalgo, Viggo Mortenson as Frank Hopkins stoops down to scrape

up some of the sand covering the arid Saudi Arabian ground where his colorful mustang will race. His expression is grim, his mouth in a frown as he studies this “track.” It’s clear he knows the surface is far from ideal for racing, even for hardy mustang hooves.

A less-than-ideal riding surface is an understandable concern. Tragic race-horse accidents frequently call the

surface they run on into question (For instance, who could forget Eight Belles’ heartrending pair of broken fetlock joints after coming in second at the 2008 Ken-tucky Derby, or Rewilding’s cannon bone break mid-race at Britain’s 2011 King George VI & Queen Elizabeth Stakes?). Upper level sport horses, like the 2010 World Equestrian Games (WEG) triple-gold dressage champion Totilas or the 2006 WEG individual eventing cham-pion Toytown, sustain lameness-causing leg injuries and have to withdraw from

major competitions. Amateur competi-tion mounts and pleasure horses might be retired early due to conditions such as navicular disease. And these scenarios call us to consider: Was it because of the ground they trotted on?

Questions like this lead researchers to study “footing,” which refers to the sur-face horses are ridden or worked on in arenas and fields and on tracks and roads. The field of footing science involves un-derstanding how different kinds of footing affect equine health.

A riding surface impacts the entire equine musculoskeletal system; here’s what researchers are learning about footing biomechanics

Footing Science

CHRISTA LESTÉ-LASSERRE

TheHorse.com/Step-by-Step

Footing type, be it all-weather (shown), natural terrain, or traditional dirt/sand, can affect a horse’s performance as well as stride length and frequency, maximum speed, and symmetry.

DAV

ID Y

OU

NG

SBS_July.indd 48 6/6/12 3:27:35 PM

49July 2012 THE HORSE TheHorse.com

Footing’s Full-Body ImpactDespite its name, footing’s influence

isn’t limited to the horse’s feet. The inter-actions between the horse’s feet and the footing create various forces that can af-fect the entire musculoskeletal system, including bones, muscles, joints, tendons, and cartilage.

Footing type (all-weather, natural ter-rain, traditional dirt/sand, etc.) is un-questionably a potential risk factor in the development of musculoskeletal disorders—most commonly tendinitis and fractures (especially in racehorses), says Nathalie Crevier-Denoix, DVM, PhD. Crevier-Denoix is head of the equine bio-mechanics and musculoskeletal pathology unit of the Veterinary School of Maisons-Alfort, France, and the French national agronomic research institution. Footing also affects racehorse and sport horse per-formance, she adds, as it can play a role in horses’ stride length and frequency, maxi-mum speed, and symmetry.

Conformation and genetic predispo-sition are risk factors for injury as well, she says, “but the advantage of footing is that it’s a risk factor that we as humans can theoretically control. So if we better understand the relationship between the footing and the development of lesions, we can help prevent their development.”

Research ChallengesStudying footing isn’t an easy task, ac-

cording to Crevier-Denoix, which could explain why researchers have completed relatively few studies on this topic. His-torically, researchers have had difficulty associating injury occurrence to particu-lar types of footing. Other factors such as the horse’s physical type, age, and train-ing program, along with general footing maintenance—which can actually be even more important that the footing itself—could play a role as well, she says.

Researching the hoof/footing interac-tion in actual practice at high speeds has also presented a significant challenge. Un-til recently it has been physically impos-sible to place the research equipment on a fast-moving animal, and the equipment was not adaptable to the high stresses the equine locomotor system undergoes in training or racing conditions.

Elin Hernlund, DVM, PhD candidate in biomechanics in the department of anatomy, physiology, and biochemistry at the Swedish University of Agricultural Sciences, in Uppsala, recently conducted

Dr. Crevier-Denoix and colleagues can measure force, trajectory, shock of impact, and corresponding vibrations in working horses’ limbs using special shoes, accelerometers, ultrasound, and photography.

CO

UR

TES

Y B

PLC

UN

IT, I

NR

A-EN

VA, F

RAN

CE

SBS_July.indd 49 6/6/12 3:27:37 PM

50 TheHorse.com THE HORSE July 2012

STEP BY STEP

a footing study on elite-level jumping horses. She used high-speed cameras to measure landing speed, angles, and direc-tions and braking speeds of each hoof as it struck, moved on, and left the ground. Her research revealed that landing speed and braking speed after a jump vary sig-nificantly from one hoof to another. But the study was limited in that she could not measure actual forces on the horse’s legs and body with camera equipment alone.

“The equipment historically used for testing (mechanical weights, cadaver hooves, etc.) often does not simulate the true conditions that the surfaces are sub-jected to when loaded by a horse,” she says. “This is a problem because footing is strain rate dependent, meaning it will respond differently depending on how fast the load is put onto the surface.”

In 2007 Michael Peterson, PhD, profes-sor of mechanical engineering at the Uni-versity of Maine, built a machine designed to simulate a Thoroughbred racehorse at a gallop. While it has been useful for moni-toring racetrack maintenance, the results have not yet been validated against the biomechanics of a living horse.

“The horse-surface interaction is com-plex; it varies between limbs (leading/trailing and fore/hind), and it depends on the horse’s weight and type and the type of movement,” says Hernlund. “It is chal-lenging to build a machine that acts like a true horse.”

In 2006 Crevier-Denoix, her colleague Henry Chateau, DVM, PhD, and biome-

chanical engineers began working with their first prototype of what has become known as the “dynamometric shoe.” This special “3-D” horseshoe, nailed into a hoof like an average steel shoe, measures force

in three spatial directions and the trajecto-ry of the center of pressure. The research-ers also attached a 3-D accelerometer to the hoof wall to evaluate the shock of impact and the corresponding vibrations.

Combined with a high-speed camera, an ultrasound system that measures force on the superficial digital flexor tendon, and a speed-measuring device, Crevier- Denoix and Chateau used the shoe to quantify hoof-ground interaction at the onset of the stance phase (the period during which the hoof is in contact with the ground) and maximal limb loading at midstance, a pa-rameter which is likely the most critical in injury occurrence.

Initially, the dynamometric shoe had to be attached to cumbersome computers via several cables, which limited the study to Standardbred trotting horses pulling a surrey. Today technological advancements have made it possible via lighter computer equipment to place dynamometric shoes on galloping racehorses and show jump-ing horses—even on two different hooves simultaneously.

In these studies researchers are un-covering certain benefits of all-weather “synthetic” footing that traditional foot-ing lacks, says Crevier-Denoix. “The all- weather waxed tracks (using wax-coated sand, rubber, fiber, etc.) have a ‘damping effect,’ ” she says, meaning they absorb energy and, therefore, reduce the shock of contact between the hoof and the ground. There’s also less maximum vertical loading at the midstance part of the horse’s step on these footing varieties.

However, these benefits are countered somewhat by a longer stance phase, es-pecially in the first part of the step (the damping phase), Crevier-Denoix says. This can make the footing feel “slower.” And there might be side effects such as lingering tendon tension and a prolonged effort sustained by the hind limbs. She acknowledges these issues require further investigation.

This is a very important issue in the U.S. racing industry, as an increasing number of synthetic surfaces are replacing tradi-tional ones (such as dirt), but it is also of

THE BIOMECHANICS OF FOOTINGFooting science is primarily an exercise in physics. It’s all about forces, vectors (direc-

tion of movement), and speed. In a living animal, the study of these aspects classifies as “biomechanics.”

When researchers delve into the biomechanics of footing, they’re looking at how different parts of the hoof strike the ground—and how the different parts of the ground strike the hoof. They’re also looking at how the hoof moves, vibrates, slides, slows down, speeds up, stops almost instantaneously (which it does even in a full-scale racing gallop), and how the ground is deformed and packed by the horse’s weight.—Christa Lesté-Lasserre

The horse-surface interaction is complex; it varies between limbs, and it depends on the

horse’s weight, type, and movement.

DR. ELIN HERNLUND

SBS_July.indd 50 6/6/12 3:27:37 PM

51July 2012 THE HORSE TheHorse.com

interest for the sport horse world. Again, further investigation into these areas is needed.

Other ConsiderationsResearchers are still a long way off from

having the right answer for all footing situations. “There is certainly footing out there that is kinder to horses’ legs, but I believe that there is no one footing that is good for all horses,” says Paul McClellan, DVM, owner of the San Dieguito Equine Group Inc., in San Marcos, Calif. “With all the different conformations and foot types and ambulatory variations (the way a horse moves over the ground), one foot-ing will suit one horse but not another.”

The horse/rider combination can also affect the hoof/footing interaction, Mc-Clellan adds. “Good riders can change the dynamics with very little effort by how they sit and balance the horse,” he says. “Researchers have put their heart and soul into the biomechanics of this business, but the real world reality is there are many complex challenges to it. Any great solu-tion is going to be slow in coming.”

Another challenge footing researchers face is the significant variation in biome-chanical forces among disciplines. “Differ-ent sports put different demands on the performance of the surface,” Hernlund says. “Grip is crucial for the show jumper, for example, but it can’t be too pronounced in a surface for reining horses that need to do slide stops.”

Cross-country course footing is per-haps one of the trickiest to manage. “It’s hard to control the amount of rainwater on natural terrain and prevent wear on the surface,” Hernlund continues. “Plus, the rooting system of the grass is crucial to prevent horses from slipping. Cross-country course designers and caretakers might have one of the most challenging situations when it comes to keeping the surface safe for all competitors.”

And it would be a mistake to assume it’s just competition surfaces owners and trainers should be concerned about, says Crevier-Denoix.

“On the competition ground, the horse is going to make maximum efforts, so it’s clear that the quality of the ground should be optimal there,” Crevier-Denoix says. “But generally speaking, musculoskeletal pathologies (tissue disease/damage) in sport horses occur over time with a build-up of training. So obviously we need to be paying attention to the footing where the

horse is training every day.”Pleasure horses are subject to injury risk

as well, she says, even though their train-ing might be less frequent or strenuous. All horses worked in harness or under saddle can develop musculoskeletal pathologies as a result of inadequate footing.

Put Your Best Footing ForwardOwners and their horses can benefit

from some common-sense footing rec-ommendations: First, be aware of your horse’s reactions to the footing, says Mc-Clellan. Knowing your horse well will help you recognize his comfort level on a day-to-day basis and gauge whether the foot-ing suits him. Also, walk and jump around on the ground yourself—is it comfortable to you? If so, it’s more likely to be comfort-able for the horse as well. Make sure the ground drains well in rainy seasons to pre-vent puddles and mud, and water it well in dry seasons to avoid excessive dust.

And be sure to maintain the footing by harrowing (dragging) it regularly. “The shock of impact on a harrowed track is twice or even three times lower than on one that hasn’t been maintained for sev-eral days,” says Crevier-Denoix.

Above all, if you find your footing isn’t right for your horse, change it. If you can’t

change it, McClellan’s advice is simple: Find another facility with better footing. Although horses tend to adapt to the sur-face they travel over, they might sustain injuries along the way or not adapt at all. Don’t rely on boots, wraps, and gadgets to help; if the problem is with the foot-ing, only changing the footing will fix the problem.

If you do have the means to change your footing, don’t simply rely on a good marketing campaign or word-of-mouth, and don’t be won over by claims of easy maintenance, McClellan says. Check with your veterinarian and read up on the latest research as it emerges.

Take-Home MessageIt might take some time before we

know exactly what kind of footing our horses need. But fortunately researchers are building on these technological devel-opments, providing the answers we need to keep equine musculoskeletal systems healthy. h

ABOUT THE AUTHORChrista Lesté-Lasserre writes fiction and nonfiction with an international perspective, specializing in equine topics. A native Texan, she rides English, breeds German Warmbloods, and raises three young equestrians in Paris, France.

Dr. Michael Peterson built a machine designed to simulate a Thoroughbred racehorse at a gallop; this tool has been useful in monitoring race track maintenance (shown here at Churchill Downs).

CO

UR

TES

Y D

R.

MIC

HAE

L PE

TER

SO

N

SBS_July.indd 51 6/6/12 3:27:39 PM