Latest research and best practices for training, competition, and your horse’s soundness
Reprinted from the June 2014 Issue of USDF Connection
By Hilary M. Clayton, BVMS, PhD, Diplomate ACVSMR, MRCVS
In the March issue, I covered the main points of the recently released Equine Surfaces White Paper, a document published by the Fédération Equestre Internationale (FEI) covering the latest in footing research (“Horse Health Connection: Technology and Footing Research”). This month, I’ll delve into practical application of the findings.
Review: Key Points Photo courtesy of the McPhail Equine Performance Center
The Equine Surfaces White Paper describes the mechanical properties of footing that affect a horse’s performance and safety. These include hardness, friction, cushioning, and rebound.
Hardness. The footing material should be soft enough to allow the hoof to sink into it immediately after it hits the ground so that the downward movement of the hoof is decelerated gradually and concussion on the limb is reduced.
Friction. Frictional resistance determines how far the hoof slides forward. Too much friction stops the hoof abruptly and contributes to concussion; too little friction allows the hoof to slide uncontrollably. Frictional resistance also stabilizes the footing so that the hoof can push off effectively.
Cushioning. Cushioning decreases stress on the limb when it is loaded by the horse’s weight.
Rebound. If the footing rebounds at the appropriate time, it may make the surface feel more lively. The recipe for appropriate hardness, friction, cushioning, and rebound is different for each sport, which presents quite a challenge in providing footing for multipurpose arenas, such as those used for both dressage and jumping. The importance of providing safe footing was underscored at the 2004 Athens Olympics, where footing problems were blamed for severe injuries to three jumpers.
Footing for Competition Arenas
Dressage horses perform a range of gaits and movements that involve different types of interactions between the hoof and the footing. Highly collected movements, such as piaffe, are performed at slow speed and are highly reliant on the horse’s having good balance. Performance is facilitated by grooming and leveling the arena so that the horse can anticipate exactly how the surface will feel during these high-precision movements.
In the extended paces, the horse must generate large propulsive forces to push off the ground into a lofty suspension. The surface needs to offer sufficient frictional resistance to support these propulsive forces, but it should also allow the fast-moving hoof to slide further forward at landing in order to avoid an increase in concussion. Evidence of hoof slide is seen when the footing sprays forward in front of the hoof (Figure 1). In lateral movements, such as half-pass, the medial (inner) and lateral (outer) edges of the hooves should be able to dig into the surface as the horse rolls sideways over the hoof (Figure 2).
By comparison, the primary footing requirement of jumping horses is security during push-off , landing, and turning. Jumpers exert much larger forces than dressage horses, both at push-off , when adequate frictional resistance is needed; and during landing, when good cushioning is required. A surface that performs optimally for jumpers is safe for dressage, but dressage riders may feel that it lacks rebound or feels “dead” to ride on. At competitions in which dressage and jumping are performed in the same arena, it is difficult to provide footing that is optimal for both disciplines, and some compromises may need to be made.
Footing Considerations During Training
Good footing is invaluable for producing a top competitive performance (Figure 3) and for maintaining long-term soundness; but it’s not necessary— and probably not in the horse’s best interest—to ride on optimal footing all the time. Horses benefit from regular exposure to a variety of footing materials and to different types of terrain (Figure 4). If their only experience is with fl at, perfectly manicured turnouts and impeccably groomed arenas, they will not be well prepared to cope with the footing challenges they may encounter at clinics or competitions. Different types of footing, uphill and downhill slopes, and uneven terrain are part of the normal equine environment. Without them, the horse is deprived of valuable sensory input that stimulates the development of appropriate coping mechanisms to protect against unexpected events, such as stepping in a hole.
Preserving your horse’s soundness is another reason to vary the surfaces you ride on. If a horse always trains on the same surface, then the same type of stress is applied to the limbs day after day, and damage may eventually accumulate to the point that it becomes evident clinically as a repetitive-strain injury. For example, although waxed-sand composite surfaces have the advantages of imposing lower concussion and providing better cushioning as compared with sand, they also have higher frictional resistance that stops the forward sliding movement of the hoof more abruptly than sand or dirt. Interestingly, some racetracks are now reverting to dirt.
A few years ago, race tracks changed from dirt to synthetic surfaces, based on the assumption that footing consistency and horse safety would be improved. The statistics show that the transition to synthetic surfaces was indeed associated with a reduction in catastrophic injuries (fractures), although some veterinarians believe that there has been a corresponding increase in soft-tissue injuries. Research is needed to determine whether dressage horses working exclusively on synthetic surfaces are predisposed to specific types of injuries.
It is important to do some training on a surface similar to what you will encounter in competitions, given that training and competing on dramatically different surfaces is likely to have a negative effect on performance. If necessary, ship to a facility where you can work on a surface similar to that installed at the show grounds at least a couple of times before the competition.
Footing Materials Turf is the traditional surface for equestrian arenas but is seldom used nowadays in top-class competition venues. The biggest problem with turf is that its mechanical properties are highly dependent on the moisture content of the soil, meaning that the weather has a major influence on the state of the footing.
The majority of arenas today are sand-based, often with other materials added. Sand varies in its mineral content and in the size and shape of the grains. The mineral content determines the hardness; harder sand is preferred in arenas because it is more durable. To determine the hardness, put a small amount of the sand on a hard surface and crush it with the back of a spoon. Soft sand will turn to powder, while hard sand will resist being crushed.
The sand grains may be more or less angular or rounded in shape. Angular grains fit together more tightly, whereas round grains tend to roll over one another like tiny ball bearings. Sand with rounded grains rolls under the horse’s hooves and shifts more with use. Angular sand with grains in a variety of sizes is more stable under foot.
The sand used in riding arenas is usually washed to remove the fine particles that turn to dust when the surface dries out. It is usually recommended that sand in a dressage arena be two to three inches deep.
The properties of sand-based footing are most affected by its moisture content. Watering increases sand’s hardness and frictional resistance. Deep, dry sand lacks stability and tends to give way as the horse pushes off , which makes it very tiring for the horse. If the rider is not careful, the early onset of fatigue associated with this type of footing can lead to soft-tissue injury.
Inconsistency in moisture content is a common problem, from wet spots caused by uneven drainage, to dry spots in areas that receive direct sunlight, to varying moisture content resulting from sprinklers that do not water the surface evenly. Inconsistent footing may cause the horse to shorten his stride, trip, slip, or lose his balance.
Additives are often mixed with sand to improve its performance as a riding surface. One inexpensive option, rubber, is available as crumbs about 0.25 inch in diameter that are mixed into the sand, or larger pieces of one to two inches in size that are laid on top of rolled sand. Rubber crumbs reduce surface compaction because the rubber pieces do not change in volume under compression; when the hoof steps on the rubber crumbs, the crumbs bulge sideways and open up pores in the sand surface. In addition to reducing compaction, rubber increases the elastic rebound of a surface.
Good footing is invaluable for producing a top competitive performance and for maintaining long-term soundness, but it’s probably not in the horse’s best interest to ride on optimal footing all the time.
Another relatively inexpensive option is wood chips. Regular and frequent arena maintenance is important rubber pieces in order to maintain surface consistency and to reduce the risk of slipping.
Other materials that are commonly added to sand are fibers, felt, and polymers. Fibers, which act in a similar manner to the roots of turf grasses, are particularly effective in stabilizing sand. There are several proprietary brands of footing, each having a specific mix of various types of natural or synthetic fibers and rubber that are added to stabilize the surface, reduce compaction, and increase elastic rebound.
The application of wax to arena surfaces binds the particles together, which improves cohesion, decreases dust, and reduces the need for watering. Waxed surfaces tend not to develop deep hoof prints, and they give the horse more security when turning. However, synthetic surfaces tend to compress with heavy use and may become harder as a competition progresses unless they are maintained with sufficient frequency.
The wax material usually consists of byproducts of the petroleum refining process, along with paraffin and other waxes. In hot climates, some components may soften and melt in the sun. If this happens, the characteristics of the surface will change. On racetracks with synthetic waxed surfaces, race times are slowest when the temperature is highest, which is due in part to melting of the wax. Cold weather also affects the characteristics of a waxed surface. The wax needs to be reapplied periodically, with the frequency depending on arena use, maintenance procedures, and the local environment.
Even if your footing is perfect, it won’t stay that way without regular maintenance, which may include watering, harrowing, leveling, and rolling (Figure 5). The goals are to reduce compaction and to maintain the consistency of the surface throughout the arena and over the course of time.
Harrowing reduces the hardness of dirt or sand footing by breaking up areas of compaction, and it fluff s up the surface by introducing air into the footing material. Rolling compresses loose footing material and levels the surface. Watering keeps dust down, and the surface tension of water also increases the footing’s hardness and frictional resistance. Deep, dry sand especially benefits from watering to reduce hoof slide at contact and to provide resistance during push off . Footing manufacturers can provide specific information regarding the ideal maintenance procedures for each type of footing.
The type and frequency of maintenance needed for your own arena depend on many factors, including construction of the base, drainage, type and depth of surface material, the local environment (including whether the arena is indoors or outdoors), how much it is used, and for what purpose. In general, dirt surfaces require more maintenance than synthetic surfaces. Removing manure and other contaminants is an important part of keeping an arena in good condition.
Dressage-specific research on arena maintenance is lacking, but in the racing world it has been shown that the fewest injuries occur in races run immediately after the track has been groomed. Inconsistency of the surface— uneven compaction, moisture, or depth—is known to increase the risk of injury. Even a small change in the way a surface is maintained may affect the way a horse moves.
The surface’s moisture content affects the adherence of the footing particles. To a point, watering increases footing’s shear strength (frictional resistance) and stability; but when the surface becomes saturated, shear strength decreases. For sand, maximal shear strength is achieved when the moisture content is between 8 and 17 percent. The optimal shear strength varies with the discipline; for dressage, it should be low enough to allow the hoof to rotate on the surface when the horse’s body is turning (Figure 6). For jumping arenas, the ideal moisture content is usually a little higher than for dressage arenas.
Before you make decisions regarding footing, consider the longer-term effects on the environment. Synthetic surfaces may pose a disposal issue because the materials will not reintegrate into the environment, and the cost of disposal in a landfill can be significant. It may be possible to reuse the material in a landscaping project, such as to create a pathway.
Although the type of footing affects your horse’s performance and safety, many materials are quite adequate for training dressage horses if they are well maintained in a manner that is appropriate for the specific type of footing. Just vary the terrain and the type of footing to reduce the risk of repetitive-strain injuries.