Half Trees and Whole Truths: The Importance of Shoulder Freedom and Wither Relief for Maximum Performance

ARTICLE WRITTEN BY DR JOANNA ROBSON FROM INSPIRITUS EQUINE

Saddles are to horses like clubs are to golfers. They are considered a necessary apparatus for successful performance, and the correct size, design, and fit can make or break your game. There are numerous articles and videos available about the importance of correct saddle-fit for maximal pain-free equine functioning, and yet most of this information is geared towards dressage horses and show jumpers, or Western performance horses. There is one distinct group of horses for which saddle-fitting is almost never addressed, and who may, in fact, be the most greatly impacted equine athlete of all – the racehorse.

Compared to the average equine athlete, racehorses are started and competed at significantly younger ages, and also are asked to perform at the highest speeds with maximum stride extensions. Additionally, while any equine athletic injury can be at least financially and emotionally draining with lost training and competition time, accidents at top racing speeds can be catastrophic or even fatal for both horse and rider. Thus, proper biomechanical health and functioning is imperative for the welfare and safety of both racehorse and jockey.

While physiological factors may be influenced by specific training and conditioning, the basic static resting equine parameters are typically the same. Thus a discussion of saddle-fitting anatomy and importance of correctly fitted tack should remain constant regardless of the horse’s discipline: jumping, dressage, racing, or working cattle. Simply put, the horse’s anatomy dictates how the saddle should fit, not the subjective desires of the rider and trainer.

Exact data on the history of saddles and trees is widely variable depending on source; however, it is generally agreed that warriors of ancient times and soldiers/cavalry riders were quick to understand that if they protected their horse’s backs, their lives were better protected and more battles were won. A saddle-tree was crafted (as early as 700 B.C.) to evenly distribute pressure and weight from rider and gear while protecting the horse’s spine and the muscles beneath it. Racehorses of ancient times were often galloped bareback or in nothing but a cloth, but as modern racing evolved, racing saddles also progressed. The desire to create a light-weight saddle for increased speed continued, and lightweight, synthetic materials were also introduced. However, this is not without inherent problems.

When we discuss saddles of any type, there usually follows a conversation of the saddle tree, the frame which may be in many different forms and many different materials and ideally distributes pressure and weight. The average race training saddle may have a half tree or a full tree. “The half tree, while being lighter, is losing popularity as it creates unwanted pressure on the horse’s spine. Full tree saddles are heavier but better for the horse’s back in the long run. This is especially important in the sport of horse racing where the jockey places all his weight in his stirrups. Since the stirrups are attached to the saddletree, the tree helps to dissipate the weight evenly instead of allowing it to accumulate in one specific point on the horse’s spine which can lead to a number of different health problems.”1

Regardless of whether a horse is a Thoroughbred racehorse, a Quarter horse reiner, or a Warmblood dressage horse, their basic anatomy is essentially identical; musculoskeletal, nervous system and circulatory system anatomy remains the same from pony to Percheron. They share specific structures that should not be impeded in order to maintain pain-free maximal performance.

The horse’s forelimbs are considered attached by a “false joint.” Only soft-tissue structures (muscles and fascia) hold the forelimbs to the trunk (horses lack a collar bone), thus any restriction of those structures can impede full range of motion through extension and retraction of the limb. The top portion of the scapula is a cartilage cap, and the rest is bone. The thin trapezius muscle which has both a cervical and a thoracic portion, plays a role in forelimb attachment and movement, and also houses sensitive nerves which when triggered can cause a hollowing of the back and raising of the head, pain in the surrounding area, and behavioral or training problems. An ill-fitted tree can literally hang on this area, directly affecting the spine and nerves, causing pain, and directly influencing performance.

When studying growth plate closure in horses, one can see that vertebral closure may take 5-7 years, and wither caps may never fully solidify. Abnormal pressure in these areas can create inflammation leading to degenerative processes and osteoarthritis, and hyperextension may also result in kissing spine. Additionally, a saddle or tree that blocks the horse’s shoulder from a normal range of motion produces a choppy gait and restricted stride -- obviously a reduced cranial phase of stride would be undesirable in a racehorse. “A biomechanical model of running has been presented. A basic premise has been that the swing time is nearly independent of speed. In fact, both the racehorse and the trotter have nearly equal swing times. Consequently, as speed increases and the stance phase becomes shorter, the horse must compensate by increasing his extension or the length of the airborne phase (or both). The overlap between the legs appears to affect both the ultimate performance potential of the horse and also his prospects for soundness.” Type of racing surface, shoeing, and tack may all influence this stride.

Improperly fitted saddles can create pinching, restricted range of motion, pain, limited performance, behavioral issues, and permanent injury. “The load under poorly fitting saddles is distributed over a smaller area than under properly fitting saddles, leading to potentially harmful pressures peaks.” If one examines the standard half-tree in many racing and training saddles, this pressure is directed into a focal spot over the horse’s withers, usually because the small headplate is too wide for the horse (no base of support). Padding is also discouraged because it adds weight. Thermographic imaging confirms this pressure and inflammation and research also supports this finding. “At canter and gallop, all 3 saddles (treed, treeless and flexible) were mainly loaded in TD(front) (>80% of the rider's weight). Additionally, “when the horse transitions to a gallop, the peak pressures escalate, while the horse’s ability to redistribute the added pressure declines.” “Though more specific testing is needed in the field with a large number of cases, Based on using lowest over all force as a criterion for saddle fit (Meschen et al. 2007), the full-tree saddle is preferable for use. High variation between individuals indicates that the appropriateness of saddle fit should be considered on an individual basis.” In the specific study of pressures under racing saddles, “It was concluded that racing saddles exert high peak pressures over bony prominences known to be sensitive to pressure.”

If it is well known that pressure on a horse’s spine can lead to pain and lameness, decreased performance, and behavioral problems, then the obvious goal should be to alleviate this pressure by any means possible. “Back pain caused by spinal muscle pathology is likely frequent in performance horses and Thoroughbred racehorses.” While padding may be a step in the right direction, a lightweight full tree that properly distributes pressure and alleviates any wither pressure and shoulder restriction would be ideal. In a recent study article on the association with equine thoracolumbar asymmetries, horse and rider health, proper saddle-fit was found to be significant in maintaining appropriate thoracolumbar symmetry and musculature, certainly desirable traits in a winning racehorse.