The type of footing on which a horse performs strongly influences whether the animal has a long and productive career, or whether it has that career cut short because of unsoundness or injury. Footing also influences how well the horse performs. Bad footing often is equated with a poor performance, and good footing frequently is equated with a stellar performance. Unfortunately, with footing, it is not a case of one size fits all.
The type of competition has a bearing on footing. The jumper, for example, requires a surface that is more yielding than does the dressage horse. The reining horse needs a surface that allows it to perform its signature sliding stop, yet is firm enough that it can demonstrate its other moves -- figure-eights and spins. The cutting horse needs a surface that is relatively deep and forgiving as it makes sudden stops and hard turns. The list goes on.
Racetrack surfaces also vary. A typical Thoroughbred racetrack is far different than a typical harness track. Because of the tremendous concussion with each stride, the track on which a Thoroughbred runs must be relatively deep and yielding. The trotter and pacer travel at gaits that are far less concussive and, as a result, race on much harder surfaces.
If we are to understand the difference between good and bad surfaces, we must first understand exactly what happens when a horse travels over that surface.
Hilary M. Clayton, BVMS, PhD, MRCVS, holder of the Mary Anne McPhail Dressage Chair in Equine Sports Medicine at Michigan State University, has spent much of her professional life studying equine locomotion. (A problem she faced at this writing involved the type of footing to be selected at the state-of-the art equestrian center being constructed at Michigan State University.)
We turn over to Clayton the portion of the discussion involving the way in which a horse travels.
The stance phase is the period during which the hoof is in contact with the ground. The following parts of the stance phase can be recognized and measured or described during gait analysis -- initial ground contact, impact phase, loading phase, and breakover.
Initial Ground Contact
The first contact of the hoof with the ground at the start of the stance phase is classified as heel first, flat-footed, or toe first. The manner of contact is influenced by gait, speed, farriery, and lameness. The hind limbs show a greater tendency for heel first contacts than the forelimbs. Heel first contacts occur more frequently during high-speed locomotion and when horses are trimmed with an upright hoof angle. The frequency of toe first contacts increases when the hoof is trimmed at an acute angle. In some movements, such as piaffe, toe first contacts are normal.
With certain types of lameness, the horse adopts an unusual gait as a means of reducing pain by shifting the loading away from the affected structures. The manner of initial ground contact is important because it affects the forces and accelerations applied to the limb during the subsequent impact phase.
This phase occupies the first 50 milliseconds (one-twentieth of a second) after the hoof contacts the ground. During this time, the limb undergoes rapid deceleration that causes a shock wave to travel up the horse's limb. The shock wave is characterized by high amplitude and a rapid vibration frequency. These characteristics are particularly damaging to the bones and joints, especially when they occur repeatedly, stride after stride, during locomotion. Prior to hoof contact with the ground, the muscles are pretensioned in accordance with the horse's expectation about how the surface will peel. The impact phase has such a short duration that there is insufficient time for the muscles to respond to unexpected changes in the surface in a manner that might protect bones and joints.
During the impact phase, the hoof is decelerated in both the vertical and horizontal directions. The fore hoof usually has a higher vertical velocity, but a lower horizontal velocity, than the hind hoof at the instant of ground contact. This might explain why there is greater concussion (defined as a combination of rapid oscillations and impulsive loading) and could be one reason for the higher incidence of chronic lameness in the forelimbs. As the shock wave travels upward through the bony column of the limb, it is attenuated (weakened) by flexion of the joint and deformation of the soft tissues.
The majority of injuries to the locomotor system occur not as a result of a single catastrophic incident, but as a consequence of the cumulative damage that occurs from the many strides taken during training and competition. Impact is the most damaging phase of the stride for the bones and joints. Factors that affect the amplitude or frequency of impact shock include speed, surface, and farriery. Faster speeds are associated with higher impact shock.
Horses which train and compete at speed often develop fatigue fractures or bone sclerosis as a consequence. Fatigue fractures are small fracture lines in bones (usually long bones) that have not adapted adequately to high-impact loading. Bone sclerosis represents over-adaptation, with the bone becoming excessively mineralized in response to high-impact loading.
A more chronic impact-related problem is degenerative joint disease, which is the most common reason for premature retirement of sport horses. The repeated traumatic effect of impact shock during years of training and competing is a primary factor in the development of degenerative joint disease, but the effects do not become apparent until permanent damage is present, and the horse becomes lame. Therefore, trainers must make every effort to reduce the effect of impact shock throughout the horse's career. This means working on good surfaces and taking care of hoof balance and shoeing.
Loading and unloading occupy the period from the end of the impact phase until breakover. During this phase, forces are applied more gradually than during impact, and without the rapid vibrations. In trotting horses, the vertical force increases steadily, peaking at midstance, after which there is a period of unloading. The longitudinal force retards the horse's forward motion during the loading phase and provides forward propulsion during unloading.
During the loading phase, the elastic structures that run down the back of the cannon region and over the fetlock are stretched. These structures, which include the deep and superficial digital flexor tendons and the suspensory ligament, store elastic energy as they lengthen.
Midstance of the forelimb occurs when the cannon segment is vertical, which corresponds with the time when the fetlock joint is maximally extended and the vertical force reaches its peak value. At midstance, the fetlock sinks to its lowest point and the joint is maximally extended. The magnitude of the peak vertical force determines the amount of fetlock joint extension.
After midstance, the vertical force declines steadily until the hoof leaves the ground. At the same time, the fetlock joint rises and flexes. During the unloading phase, tension in the flexor tendons and the suspensory ligament is reduced, and they start to recoil elastically. The release of the elastic energy helps flex the distal (lower) limbs during the subsequent swing phase. The longitudinal force is propulsive during the unloading phase.
This begins when the heel leaves the ground and starts rotating over the toe of the hoof, which is still in contact with the ground. Breakover is initiated by tension in the distal check ligament acting through the deep digital flexor tendon, combined with tension in the navicular ligaments.
On a hard surface, the hoof remains flat on the ground until heel liftoff. On a softer surface, the toe rotates into the surface prior to heel liftoff, which reduces tension on the distal check ligament, deep digital flexor tendon, and navicular ligaments. This, in turn, reduces pressure in the navicular region. Therefore, a surface that allows the toe to dig in during push-off usually is beneficial, especially for horses with navicular syndrome or other types of caudal heel pain. Toe liftoff is the instant when the toe leaves the ground, after which the elastic tendons and ligaments are able to recoil and flex the joints.
In the swing phase, the limb is initially protracted (pulled forward) then, in the final part of the swing phase, it is retracted (pulled backward) prior to initial ground contact. The purpose of this "swing phase retraction" is to reduce the horizontal velocity between the hoof and ground at initial ground contact. The swing phase retraction has a considerably longer duration in the forelimbs than in the hind limbs, and this explains why the horizontal velocity is lower in the forelimb than the hindlimb at ground contact.
During the swing phase, the limbs act in a pendulum-like manner. The forelimb rotates with its pivot point in the upper part of the scapula. Since horses do not have a clavicle or a shoulder girdle, the whole scapula is free to rotate back and forth on the side of the chest wall. The hind limb rotates around the hip joint in the walk and trot and around the lumbosacral joint (just in front of the croup) in the canter and gallop. The lumbosacral joint is the only part of the vertebral column from the base of the neck to the tail that allows a significant amount of flexing (rounding) and extension (hollowing) of the back. At all the other vertebral joints, the amount of motion is much smaller. Moving the point of rotation from the hip joint to the lumbosacral joint increases the effective length of the hind limbs, therefore increasing stride length.
Movements of the proximal (upper) limbs are the result of muscular action. Movements of the distal limbs tend to follow passively -- without active muscular contraction and as a result of inertial forces. When the hoof leaves the ground, elastic recoil of the flexor tendons and the suspensory ligament raises the hoof, pastern, and cannon to initiate flexion of the carpal (knee), fetlock, and coffin joints. In the later part of the swing phase, these joints are extended in preparation for the next ground contact. In the hind limb, flexion and extension of the stifle, hock, and fetlock joints are coupled through the action of the reciprocal apparatus, which consists of strong, thick tendinous bands on the front and back of the limb.
Surface To Surface
With that thorough explanation from Clayton as background, we now can turn our attention to footing that either helps or hinders a horse as it goes through the various stride sequences.
There are extremes at either end of the spectrum -- a surface that is much too hard or a surface that is much too soft.
A hard surface, such as concrete or sun-baked clay, says Clayton, has high-impact resistance because it absorbs little, if any, of the impact energy. Consequently, the impact shock wave of the loading phase of a step must be absorbed almost entirely by the loaded leg. This means that high-impact resistance is associated with heavy concussion.
"Horses working on such surfaces," says Clayton, "tend to move conservatively in order to avoid excessive shock to their limbs. Under these conditions, riders find that their normally free-moving horses have become short-strided and stiff as they struggle to protect themselves against the unfriendly footing."
At the opposite end of the scale, other footings -- such as deep wood shavings -- create a surface that has low-impact resistance. This type of surface absorbs the energy of the footfall, thus reducing concussion on the legs. But at the same time, it requires a great deal of energy on the part of the horse to provide forward and upward propulsion.
"Normally," says Clayton, "a horse's leg stores some elastic energy in the ligaments and tendons during loading that is released to bounce the leg off the ground during unloading. To imagine what it is like for your horse to work on deep wood shavings, think of running on a track covered in pillows. This type of low-impact surface absorbs so much energy that your -- or your horse's -- muscles work much harder to provide sufficient propulsion. It has the effect of transforming a bouncy basketball into a medicine ball, and when this happens, there is premature onset of fatigue."
Riders should be aware of fatigue factors, says Clayton, such as raised heartrate, labored breathing, profuse sweating, and a detioration of performance.
When a horse is fatigued, there is a much higher risk of injury to muscles, tendons, and ligaments, and the potential for tying-up also is increased, says Clayton.
Time to learn still another new term -- shear resistance.
This term describes the resistance of the surface to penetration, for example, by the toe of the hoof during the push-off phase of a stride.
"Ideally," says Clayton, "the toe should be able to penetrate the surface in the terminal (end) part of the push-off. It is at this time that the navicular region experiences the highest forces. The higher the density of compaction of the footing, the higher is the shear resistance, making it more difficult for the toe to dig in. This explains why horses with navicular disease cannot perform well on hard footing."
On the other side of the coin is a loose surface, such as deep, dry sand or shavings. In these cases, the shear resistance is low so that the toe penetrates easily, but because the footing continues to yield during the critical push-off phase, it provides little or no support to the foot.
"Consequently," says Clayton, "the muscles must work harder to produce the necessary propulsion. Low shear resistance -- a condition referred to on racetracks as a 'cuppy track' -- not only leads to a rapid onset of fatigue, but because of the instability, invites excessive lateral movement in the joints and thus increases the possibility of sprains -- a condition exacerbated by fatigue."
Friction between hoof and ground is another important aspect of footing. As the word implies, friction determines the amount of resistance when the hoof is sliding over the surface.
When the hoof makes contact with the ground, it is traveling forward. If friction is high, the hoof will stop abruptly. friction equates to dramatically increased shock waves to the limbs.
If friction is too low, the foot might slide forward uncontrollably.
Not only does inappropriate friction set the stage for injury, it also can have a detrimental effect on a horse's attitude and performance.
In discussing inappropriate friction, Clayton used dressage horses as an example in explaining how it can affect performance.
"Either too much or too little friction reduces your horse's confidence in the surface and causes him to step shorter and adopt a shuffling gait, losing impulsion altogether. It often takes a horse a while to regain his trust in his footing, so even if the footing in the show ring is inviting; when you have to warm up on slippery grass or trappy mud, your horse may go through an entire test before he feels secure enough to 'loosen up.' Too much time spent riding on high- or low-friction surfaces risks making long-term changes in your horse's posture and locomotion."
The next question to Clayton is an obvious one: What constitutes ideal footing?
"Ideally, an arena surface is somewhat deformable to absorb impact energy, yet sufficiently resilient to give the horse more spring. It allows him to move so that his hooves slide gently into the loading phase. It provides penetration during breakover as well as stability during pushoff."
The next question is just as obvious. How does one go about making this ideal surface?
This can vary from one region to another, she says, with materials also varying.
In 1995, Klaus Fraessdorf won the United States Dressage Federation Footing Award for the footing in his main ring at the Clarcona Horseman's Park in Orlando, Fla.
Fraessdorf's ring was a mixture of screened limestone (30% and shredded (pea size) car tires (70%). The surface, which is three to four inches deep, allows a 1 1/2-half inch indentation by the horse. It lies on an extremely hard bed of limestone that has been compacted to the density of a highway roadbed. Because of the sandy Florida soil, it needs no other drainage system.
The riding rings at Tempel Farms in Illinois provide excellent footing, but with different materials than those used in Florida. It is at Tempel Farms that the Champion Young Rider in dressage has been determined for the past decade.
Tempel Farms enlisted the aid of Hermann Duckek, an internationally renowned footing expert. The surface of the main arena is comprised of an equal mixture of No. 2 sand, the kind used on baseball diamonds, and bagged pine shavings to a total depth of no more than two inches. The ring sits on a rock-hard base of four to five inches of screened limestone. The limestone was laid on hard clay that was carefully left undisturbed during the process of removing the rich Illinois topsoil.
As mentioned earlier, locale can have a bearing on what materials are used. In Oregon, western Washington, and British Columbia, makers use a tanbark indigenous to the area. It is heavier than shavings, so that on impact it condenses to provide stability in the loading and breakover phases of the step while increasing energy in the unloading phase. The character of the bark and natural soil is such that these rings also require no drainage other than an engineered crowning of the ring.
Across the country in Virginia and Maryland, show rings use crushed rock or limestone, often mixed with sand. The sand prevents the limestone from compacting. They sometimes add pea-size wood chips or rubber for buoyancy. The absorbency of the stone precludes the necessity of additional drainage as the rings remain stable even under standing water.
Mix And Match
It is obvious that there is no single magic formula for good footing, and that a variety of products in a variety of combinations are being used.
However, there does appear to be one basic requirement that must be met whether one is providing footing on a racetrack or in a performance arena -- a base that is level and so hard that it can't be penetrated by a hoof. As already mentioned, a common material for this hard base is crushed limestone. The other requirement is that the surface material that covers this base must have elasticity because the base has none.
There is a great variety of surface materials available today, ranging from ordinary sand to such exotic components as coconut fibers and shredded athletic shoes and car tires.
A company that specializes in providing arena footings is Footings Unlimited, which is headquartered near St. Louis, Mo. The company, which advertises itself as "offering the largest selection of footing products in North America," also is quick to point out that no two riding arenas are exactly alike and different disciplines require different footings.
In its promotional literature, the company discusses the complexities involved in obtaining and maintaining good footing.
"Before you make any purchase, you need to decide just what it is you are trying to accomplish. Do you want to reduce dust, improve drainage, reduce shock, reduce watering, eliminate packing, modify take-off resistance, improve uniformity of density, improve grip, increase versatility, reduce dragging and maintenance, minimize effects of freezing, or increase/ decrease depth?
"As you can see, there is a bit of thought that needs to go into deciding just what you want from your arena footing. Unfortunately, you can't have it all. If any manufacturer tells you their product can do it all, you would probably do better to look elsewhere. No footing on the market today is dust-free, and all footing breaks down over time.
"There is, however, one thing you can be absolutely sure of -- maintenance is the key to good footing. Properly designed maintenance programs may very well save you the cost of replacing your footing. There are many things that can be done to improve your footing that involve little more than some time and creativity."
One component that has become popular in the footing world is rubber, either from tires or tennis shoes. A case in point involves the Empire Polo Club and Equestrian Center in Indio, Calif. Center management decided they wanted the surface of the training rings to be more forgiving for the jumpers that were preparing for a major competition.
To accomplish this goal, the training rings were covered with the shredded remains of 80,000 pairs of Nike athletic shoes. The shredded material was mixed in with existing sand to provide a more resilient surface.
Wayne Gregory, general manager of Footings Unlimited, said that his company sold about 200,000 pounds of material to the equestrian center at 25 cents a pound.
The shredded shoes, he reported, were rejects from Nike and not worn-out shoes. The uppers of the shoes were turned into fluff and the soles were ground into bits of rubber.
The shredded rubber used in arenas has variations. For example, Footings Unlimited offers the product in nine different sizes, four quality grades, and 45 colors. Colors are made from virgin rubber. The size and quality will depend on what it is being mixed with in the arena.
In some instances, if the size of the rubber is too large, it will come to the surface of the arena. On the other hand, if the rubber pieces are too small, they can become airborne and simply blow away creating a dust problem. About the only way to determine what type of rubber product is appropriate is first to have the material of the existing arena analyzed. Only then can it be determined what type of rubber should be added.
Nutty But Nice
Perhaps the most exotic arena footing material on the market is a substance made from coconut fibers. It also is one of the more expensive materials.
Natural coconut fibers, say its supporters, absorb shock, reduce compaction, improve traction, and help the arena maintain a proper moisture content. Coco-nut fibers have great strength. The fibers are extracted from the husk of the coconut through a time-consuming process that takes more than three years. The husks are placed in netted bags and hung in the sea for a year. Then they are taken out and beaten to soften them. The process is repeated again the following year, and ultimately, in the third year, the fibers are carefully separated.
The fibers then are converted into a commercial product that is designed to be mixed with the dirt or sand of an existing footing.
Another footing material available to horsemen is polymer-coated sand. A similar substance, called Equitrack, was installed at Remington Race Track when it was constructed in Oklahoma City. The coated grains of sand compress when a horse's foot makes impact, providing both resiliency and proper shear resistance. While horses at Remington Park had fewer leg injuries than runners on conventional surfaces, Equitrack eventually was removed and replaced with a conventional surface.
Today, material of the same type has found a home in a number of arenas. In addition to its resiliency and appropriate shear resistance, it is as dust-free as a footing can be and needs no watering.
Fibresand is another material used with success on a couple of raceracks in England and was the footing for the World Equestrian Games in Stockholm.
It is a mixture of silica sand and tough, rot-proof synthetic fibers. One of the reasons for experimenting with the material in England was the difficulty involved in maintaining the traditional turf tracks during the frequent wet spells, especially during the winter months. Water infiltrates quickly through the material, and it is resistant to freezing.
Also available for today's arenas are plastic granules that are used to loosen tight clay footing.
Various components are available for treatment of footing materials, ranging from oil-based products to organic soil conditioners. A number of companies are competing for their market share with these products or others that are similar.
Back To Basics
While there are many variables for footing, there are some basic constants if you are building or renovating an arena.
For example, the arena should be located on dry, well-draining ground. The arena site should be level with a slight (one- to two-degree grade) to allow rain water to pass through the surface and flow off the base.
The base might be naturally occurring material or something that is added. Whatever the case, the base must contain no stones, and it needs to be packed or tamped as hard as concrete.
Before starting a project or adding material, one should find out what is already there by having the footing evaluated by a soil testing laboratory.
Once an arena is established that meets the above requirements for the discipline involved, one can rest assured that the footing should enhance, rather than detract, from the horse's performance capability and its desire to perform at an optimum level. And, most importantly, it should help to keep the animal sound throughout its career.
Away From Home
However, other problems can crop up. What if you head off to a show and find footing in the arena inadequate? The important thing is that first consideration be given to the horse. Anything less can have dire consequences.
For example, several years ago at a mid-Atlantic dressage show, four inches of new sand were added to the show ring the night before the performance. One of the competitors whose horse had not been conditioned on that type of surface decided to show on it anyway. The result was that he permanently compromised his horse's soundness.
This writer can recall arriving at a mid-western cutting arena to find that the footing was comprised of worked up heavy loam with many clods of dirt that were rock-hard. While some cutters opted to ride, another group of us simply loaded up and headed home. I don't know that any of the competing horses suffered injury, but I do know that those of us who left without competing did so with sound horses.
On another occasion, some dressage riders used an innovative approach to solve a problem. The competitors arrived at a prestigious east coast show to find the surfaces of the warm-up rings hard and unyielding. Fearing that the hard surface would bruise their horses' feet, the innovative riders rose at dawn and used the outer perimeters of the "groomed to perfection" show ring for schooling.
It's very important, Clayton emphasizes, that the horse train regularly on good footing in his home arena. Perhaps your horse can get by performing occasionally on bad footing at a show arena, she says, but soundness could be severely compromised if the horse trains daily on bad footing at home.
As was stated at the outset, one size doesn't fit all in the matter of footing. We have learned from Clayton why good footing is so important if our horses are to remain sound and perform well. Just what it takes to provide that kind of footing in different locales varies. The important thing is that the footing be suitable for the discipline involved. Determining just what that footing should be might require help from an expert in the field. At the very least, one should seek advice from someone experienced with footing. h
Editor's Note: Dr. Hillary Clayton is involved in research of footing surfaces to help horse owners; however she does not do consulting work. In seeking advice from a footing expert, please choose a company that does consulting in this area.
About the Author
Les Sellnow is a free-lance writer based near Riverton, Wyo. He specializes in articles on equine research, and operates a ranch where he raises horses and livestock. He has authored several fiction and non-fiction books, including Understanding Equine Lameness and Understanding The Young Horse, published by Eclipse Press and available at www.exclusivelyequine.com or by calling 800/582-5604.
POLL: Radiographs for Hoof Care