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Lydia F. Miller, D.V.M., AAEP Owner Education Director
What makes one footing better than another? Is it possible to find a surface that maximizes your horse’s athletic potential while at the same time protects him from injury? And what can you as owner, trainer or rider do to bring out your horse’s best and maintain his soundness when faced with less than ideal footing?
Ideal footing varies with the sport, local climate, natural ground type and gradient, and location (indoors or outdoors). It is easier to choose a suitable surface for a single sport in an indoor arena than it is to cater to the needs of several different sports in an outdoor arena, where the unpredictable effects of the weather play a role. The capital investment and the practicalities of maintaining the surface on a day-to-day basis are also important. As a result, the end product is often a compromise between the ideal and the practical/affordable, which may not be in the best interest of the horse. In this article, how horses move will be taken into account with footing in order to help reduce the risk of performance-related injuries.
By studying equine biomechanics, or how horses move, researchers have been able to tell what part of the hoof or limb is undergoing stress during each phase of the stride. Although it seems that the more we uncover about gaits the more there is to uncover, fortunately much of what has been done in human biomechanics can be applied to horses.
For example, in people, the repeated shock of impact with the ground is responsible for the development of osteoarthritis (degenerative joint disease or DJD). Activities that involve running or jumping--in which there is an airborne phase--are much more damaging than walking or stepping--in which there is always at least one foot on the ground. This is why people tend to get fewer injuries when doing low impact aerobics. Similarly, the shock of impact of the hoof with the ground is the most important phase of the stride in relation to the development of DJD in the horse. A description of the chain of events that occurs as the hoof contacts the ground helps explain why this is so.
As the hoof approaches the ground, it is moving forward and downward. At the instant the hoof strikes the ground, it is rapidly slowed down. Although the hoof acts as the initial shock absorber for the skeletal system, this rapid "deceleration" sends a shock wave up the horse’s limb. As the shock wave travels up the limb, two specific types of tissue aid in its dispersion: bone and cartilage. While bone is a fairly efficient shock absorber, excessive impact shocks may lead to microfractures. Cartilage is an even more effective shock absorber than bone, but because it is present in such a thin layer in the joints it makes a relatively small contribution to reducing the shock impact. Repeated impacts, especially of great force, can lead to progressive and irreparable cartilage damage, eventually resulting in DJD.
Effects of Footing
Reducing impact shock, then, is one aspect of footing that should be considered when choosing or evaluating a work surface for performance horses. "Impact resistance" is the term used to describe the ability of footing to absorb impact energy. It affects primarily the hoof’s downward motion. Surfaces with high impact resistance (e.g. concrete) absorb little energy on impact and are associated with high impact shock. Surfaces with lower impact resistance (e.g. wood chips) absorb more energy on impact and result in lower impact shock.
It is useful to compare the physical characteristics of different surfaces in relation to their effect on the horse. Hard surfaces such as concrete, asphalt and hard soil have high impact resistance. Consequently, the limbs are rapidly decelerated after contact leading to high impact forces and considerable concussion. Because hard surfaces also do not allow the toe of the hoof to penetrate, there is great pressure applied to the navicular region. Therefore, hard surfaces are particularly damaging to horses with navicular problems.
Sand, on the other hand, has a somewhat lower impact resistance than hard soil. However, deep or dry sand can lead to injuries other than those caused by impact shock. In addition, the horse must use a greater muscular effort to overcome the tendency of sand to give way underfoot. The working heart rate can be up to 50% greater on deep or dry sand, which explains why sand is so tiring for horses to work on. Anyone who has run on a beach has experienced this phenomenon for themselves.
Characteristics of turf, including its impact resistance, depend on several factors, notably the moisture content of the soil. For example, as the soil dries out, the impact resistance increases. Although a high moisture content lowers the impact resistance, too much moisture allows slipping. Well-maintained turf provides excellent footing, but it is difficult to keep the turf in this condition. Deterioration in surface characteristics under conditions of drought or excess rainfall is a problem for turf arenas and tracks.
There are many more components of footing that affect your horse’s potential for performance (and potential for injury) than are presented here. The best suggestion for reducing the risk of acute and chronic injuries due to footing is to use common sense:
Try to train on the same type of footing that you will be competing on. Abrupt changes in footing are one of the leading causes of injuries.
Avoid inconsistent footing. Surfaces that have soft and hard spots, deep and shallow spots, or dry and slick spots can be dangerous.
Make sure your horse is trained and conditioned for the job you are asking him to do. On the other hand, overtraining and overconditioning a horse can also lead to injuries as fatigue enters the picture.
And finally, eliminate or reduce the effects of other causes of performance-related injuries such as shoeing; training, conditioning and competition schedules; conformation; and pre-existing conditions.
Your local veterinarian can be a great place to get started learning more about all the things discussed in this article. In addition, your local extension office will have information specific to your region; organizations representing your specific breed and discipline may have information specific to your sport. Footing companies are another excellent resource as are pamphlets and books such as "Under Foot" by the United States Dressage Federation and The Equine Arena Handbook by Robert Malmgren from Colorado State University.
This article was written with the help of Hilary Clayton, BVMS, PhD, MRCVS, Mary Anne McPhail Dressage Chair in Equine Sports Medicine at the Michigan State University College of Veterinary Medicine www.cvm.msu.edu/dressage and Annual Convention Proceedings of the American Association of Equine Practitioners (AAEP) 1990-1999, of which she is an active member.
AAEP Mission Statement: To improve the health and welfare of the horse, to further the professional development of its members, and to provide resources and leadership for the benefit of the equine industry.
AAEP contact information: 4075 Iron Works Parkway, Lexington, KY 40511 606/233-0147 www.aaep.org