How the surfaces we ride on affect our horses’ soundness
In tedious rush-hour traffic one October evening in Paris, American show jumper and Olympic silver medalist Kent Farrington, dressed in a black suit and tie, spoke with me about footing. Uceko, he said in his relaxed Chicago accent, likes “big grassy fields.” The 2017 Longines Fédération Equestre Internationale (FEI) World’s Best Jumping Rider, on his way to claim his award at the Hotel de Ville, explained how it’s important to know your horse and his footing preferences.
At home in Wellington, Florida, Farrington has two sand arenas, one grass field, and a dirt track. He trains his horses on all four, as well as on trails. The idea, he said, is to encourage good mental health by changing up the environments. But equally important, he added, is promoting good musculoskeletal health.
In his experience, he said, “varying footing helps prevent injuries,” noting he’d read recent scientific studies to support this. “So in addition to keeping their minds fresh, alternating the workplace makes horses stronger and improves the health of their ligaments and feet.”
Farrington puts this knowledge into practice—with good results. His horses Uceko and Gazelle, for instance, have remained sound and competing in five-star events well into their mid- to late teens.
Still, there’s a lot scientists don’t know about footing and its connection to lameness and other health issues. Equestrians, event organizers, barn managers, and even researchers don’t always agree on which footing is best in which situations, and why. Whether it’s hard sand, soft sand, dirt, mud, turf (grass), synthetic mixes, concrete, or asphalt, each footing has its own variants.
The Limb-to-Surface Dynamic
To understand the effects of footing on equine locomotor systems, it’s important to visualize what happens when the hoof hits the ground. Think of it as a collision of different force types in various directions and intensities that evolve throughout the milliseconds the hoof is in contact with the surface. The hoof and the footing are constantly moving and reacting to each other’s forces until the foot becomes airborne again, says Nathalie Crevier-Denoix, DVM, PhD, Dipl. ACVSMR, of the Equine Biomechanics and Musculoskeletal Pathology department of the Ecole Nationale Vétérinaire d’Alfort (ENVA), in France.
Using a force-measuring shoe on a moving horse, combined with 1,000-frame-per-second video recordings, Crevier-Denoix and her team have analyzed in detail how hooves and surfaces react during the “stance” phase of a stride (when the foot is in contact with the ground). Their work reveals the multiple forces exerted in many directions, the vibration of the foot, speeds, acceleration and deceleration rates, and every angle of every structure within the leg and foot—joints, tendons, ligaments, etc.—at any precise instant of the stance. With wireless technology they’re collecting this data for each of the four feet during all gaits, in straight lines and while turning and jumping.
Dynamics vary between disciplines, horses, gaits, and even feet within the same movement, she says. For example, they noted a distinct difference in the foot-surface interaction between the leading and trailing forelimbs during canter and jumping. In jumping the trailing limb lands first and experiences the highest forces, which are vertical.
The leading limb lands next and with- stands lower forces, but it comes into the surface “progressively” and at an oblique angle—putting it at greater risk of injury, especially if the footing doesn’t cushion the blow appropriately.
“Is the footing deforming?” Crevier-Denoix asks. “If not, the foot is.”
“We can’t really move forward with understanding the effects of footing on horses’ biomechanics and health until we can first agree on how we’re describing the footing,” says Lars Roepstorff, DVM, PhD, professor of equine functional anatomy at the Swedish University of Agricultural Sciences, in Uppsala.
So, one scientific objective is simply getting people to “speak the same language” when they’re characterizing surfaces, he says.
While Crevier-Denoix’s shoe is an invaluable tool in understanding how a horse reacts to a surface, it’s not one that can be used as a global standard because it would require using the same horse, Roepstorff says. A machine developed by Mick Peterson, MS, PhD, executive director of the Racing Surfaces Testing Laboratory and professor of biosystems and agricultural engineering at the University of Kentucky, in Lexington, on the other hand, drops weight into surfaces to mimic the loads and speed of a moving horse.
While the method doesn’t use an equine limb, it applies the same force and movement to the footing every time to allow for standardized verifications, he says.
The goal is to provide riders with comprehensible and comparable descriptions of surfaces, says Roepstorff. “It’s not to say if the surface is ‘good’ or ‘bad’ but to rate various aspects on a scale so people can learn to associate that rating with what they feel,” he says. “But that has to start with a more universal language.”
That language includes terms such as cushion, firmness, grip, responsiveness, and consistency. Currently, though, there’s “not even a consensus yet on what ‘soft’ and ‘hard’ mean,” Crevier-Denoix says. Objective measurement should help, she adds, but if it’s going to provide reliable information about injury risks, the tool needs to reproduce the movement and timing of a horse foot.
The Sweet Spot
Although not officially defined, the terms hard and soft footing basically indicate whether the ground deforms and to what degree, Crevier-Denoix says.
Hard surfaces, including dry dirt and pavement, are associated with lower limb lesions, including in the pastern, fetlock, and coffin joints, in clinical cases, says Jean-Marie Denoix, DVM, PhD, director of ENVA’s Centre d’Imagerie et de Recherche sur les Affections Locomotrices Equines. If these surfaces are irregular and hard (e.g., frozen pastures in winter), resulting in uneven foot placement and torque on the lower leg bones, the injuries are worse.
Crevier-Denoix’s research also reveals “obvious” correlations between hard surfaces and superficial digital flexor tendon (SDFT) injury risk, she says. She found that Standardbreds trained on hard sand were far more likely to have early signs of SDFT and fetlock damage visible during image-based screening within four months than those training on soft sand.
Meanwhile, in horses jumping on a sand-fiber-mix footing, she noted increased impact shock and vertical loading rate on limbs—increasing injury risk—when the softer top layer was only 7 cm thick compared to a cushier 13 or 20 cm. “If you try to cut costs with a thinner top layer, you’re just going to end up with more lameness,” she says.
Hard surfaces are even more problematic with repetitive training, long rides over extended distances, and/or frequent circling, says Denoix. “Riding club horses experience more trauma to the lower joints when they’re constantly turning in circles in hard-surface arenas,” he says.
Endurance horses face similar risks because of distance traveled. “They’re covering 100 kilometers (62 miles) or more, so if the ground is hard, this isn’t going to be ideal for their joints, and (they) could even develop ‘road founder,’ a form of laminitis,” he says.
However, the occasional cross-country run on firm ground is less likely to be a risk factor for joint injury because the distance is shorter and the number of jumps doesn’t compare to the “repetition of strides” experienced in disciplines such as endurance, he adds.
Risks can multiply due to the nature of a hard surface, says Crevier-Denoix. Firm footing provides better push-off, making horses move faster. This creates a “double penalty” because higher speeds are, themselves, a risk factor for injury, she says.
Riders need not avoid hard surfaces altogether, however. Horses can adapt to working on roads (e.g., police horse patrols, road hacks, etc.) without significant injury risk, provided they start slowly and increase work gradually, says Roepstorff.
Hard surfaces can even be beneficial in some scenarios, such as during tendon healing. “When they’re already healing well, after about four months or so, short trotting sessions of just a few minutes at a time on hard ground can help promote remodeling,” if done under a veterinarian’s guidance, says Crevier-Denoix.
On the flip side, a surface that’s too soft can create issues for the tendons, says Denoix. “Again, we see issues with riding club horses, this time the ones working continuously in soft or deep sand arenas where their tendons are constantly solicited, predisposing them to digital flexor tendinitis (of either the deep or superficial digital flexor tendon) or suspensory (ligament, which lies beneath the tendons) disease,” he says.
The fetlock stays extended for long periods when the ground is too soft, Crevier-Denoix says. This slows the horse down, which reduces speed-related injury risks but can, again, predispose him to soft tissue injury. Notably, horses with a history of tendon injury should avoid very soft footing, she says. Ideally, they should work on “soft but firm” surfaces.
In areas such as stalls and walkways, footing has little bearing on soundness, provided it’s deep enough to allow horses to avoid twisting their fetlocks—which are hinge joints and don’t pivot—when getting up and lying down, says Roepstorff. “The intensity is low since they’re mostly just standing, and the horses’ bodies usually adjust well,” he says.
Moisture: A Delicate Balance
Water can be troublesome for all sorts of surface types, our sources say. Too much or too little can create significant footing issues that can lead to lameness.
“If you don’t water your arena it gets too deep and soft and, by contrast, if you water it too much, it gets too firm and compact and even becomes hard,” Denoix says. “Hardness is especially detrimental in sport horses, as short turns induce rotational stresses on distal (lower) joints.”
Think about walking on a sandy beach, says Crevier-Denoix. “The closer to the water you get, the harder the sand gets,” she says. “Where there’s no water at all, it’s so soft and deep it’s hard to walk, but at the water’s limit it’s very hard. Your best footing is where it’s firm but still a little soft.”
Synthetic footing isn’t as likely to harden due to moisture, says Peterson. but it’s still at risk of flooding if drainage isn’t ideal.
Water in footing can also freeze, making an entire surface hard, he adds. Worse, when weather cycles between above and below freezing daily, horses’ hooves can make imprints in soft footing that later freeze. “This creates serious inconsistencies in the footing, in addition to being hard, making it doubly dangerous,” Peterson says.
Consistency Is King
No matter what footing material you use, keeping your horse injury-free requires consistency across that material, our sources say. The various qualities—cushion, firmness, responsiveness, grip—must be the same across the entire surface where the horse will be working.
“When you change the properties under the horse’s feet, you’re putting that horse at risk,” says Peterson.
That’s because the horse adapts to the surface he’s working on; a sudden change can result in inappropriate forces—such as striking the ground too hard, says Crevier-Denoix. “A good example is a dirt surface where suddenly the horse runs into slippery mud, and he slides,” she says.
Varying moisture content—caused, for example, by different drying times after rainfall, especially if parts of a surface are shaded—can cause areas to have inconsistent firmness or grip, Peterson says.
The solution to moisture and inconsistency is fairly simple: Maintain the surface. “Harrowing and rolling can make a huge difference in both water content and consistency,” Peterson says. Rolling can “block out” incoming rain, and harrowing can open the surface to help it dry out evenly. “Maintenance makes a huge difference in injury risk,” he adds.
In her study on sand-fiber mix footing, Crevier-Denoix found that rolling created landing forces and angles that put jumping horses at greater risk of injury compared to harrowing, she says. But even a harrowed arena can lose its benefits if it gets compacted from frequent use.
This compacting caused by treading hooves doesn’t just happen when training at home, it happens in competition, too. “Think about show jumping,” Peterson says. “These horses follow the same path and compact that surface with each stride and jump. There’s going to be a competitive advantage for earlier hors
Consistent, With Variation
You want your footing consistent across a training surface, but for optimum orthopedic health you want to switch up the surfaces on which you train. Horses can adapt to these surfaces, provided they have the chance to do so gradually, our sources say.
“It’s important to habituate horses to different surfaces, from very soft to relatively firm, so that his bones and muscle coordination can adapt and the stresses on tendon are better adjusted by the nervous system,” says Denoix.
A gradual buildup—starting with slow gaits for 10 to 15 minutes at a time—on new surfaces allow the horse’s musculoskeletal system to adjust, Roepstorff says.
The body adapts by sustaining microscopic damage to bone—in particular, subchondral bone, which lies beneath and supports joint surface cartilage—and then remodeling. But taking it slowly is critical. Fatigue fractures and other lesions occur when the remodeling process can’t keep up with the rate of damage.
Roepstorff says one of his favorite surface-related training methods is “road work on tarmac or hard gravel, by working up gradually in intensity and amount. It’s a very good example of understanding that there are no poor surfaces, only poor use of surfaces.”
Know Your Horse and Your Surface
If there is an “ideal” surface, says Roepstorff, it’s a very broad category of surfaces due to the many factors at play.
One of the main factors is your horse, he says. Depending on his conformation, discipline, genetics, prior health issues, and personal preferences, your horse will probably work better and have less risk of injury on certain surfaces than others.
To determine what that surface is, know your horse and surfaces in general. “Read up on the properties, biomechanics, and characteristics of the different kinds of surfaces,” Roepstorff says. “Get familiar with terminology and textures, and know how these surfaces feel.”
That doesn’t mean going out and stomping around the arena—although you could, says Roepstorff. “The best way is to … listen to your horse,” he says. “Do you feel him changing his gait or his willingness to move? Consider how he acts on different surfaces, and keep in mind that this could always relate back to injury or soreness.” If you notice different behavior on a new surface, give him time to adapt.
Roepstorff’s team developed a thorough, easy-to-follow, science-based footing guide that riders can download from the FEI at bit.ly/3doVXIt. “It’s a great way to understand how complex the horse-footing dynamic is and how it can affect the biomechanics—and, therefore, the soundness—of the horse,” he says.
The footing beneath your horse’s feet affects his overall soundness. As studies on surfaces continue, we’re finding that the horse/ground dynamic is extremely complex, and there is no perfect surface for all situations. Likewise, as long as it’s well-maintained and consistent, there’s no terrible one for all situations, either. The best riders can do today is know their horses and their surfaces and make sound decisions about riding on them.