Reducing the pressure points - Scientists discover performance benefits of relieving five key pressure points under tack

Researchers detected peak pressures under commonly used tack that were of a magnitude high enough to cause pain and tissue damage. When horses have to manage this type of discomfort on a daily basis, they develop a locomotor compensatory strategy. Over time, this can lead to tension and restriction that inevitably affects performance. Physio interventions will usually ease the symptoms of tightness and soreness and, after a period of rest, performance may be restored and improved. However, this costly course of action only addresses the secondary problem. If the primary cause is still apparent—in this case pressure from badly designed or ill-fitting tack—the compensatory gait strategy will be adopted again, the tension will return, and the cycle will repeat.

Reducing the pressure that forces a horse to adopt a compensatory gait will not only improve performance, but it will also help prevent further issues which could have veterinary implications and reduce susceptibility to injury in the long term.

Saddle up 

When scientists tested the three most commonly used exercise saddles, they discovered every saddle in the test impinged on the area around the 10th-13th thoracic vertebrae (T10-T13)—a region at the base of the wither where there is concentrated muscle activity related to locomotion and posture. The longissimus dorsi muscle is directly involved in the control and stabilisation of dynamic spinal movement and it is most active at T12 (see fig 1).

Dynamic stability is the combination of strength and suppleness—not to be confused with stiffness—and is essential for the galloping thoroughbred. The horse’s back moves in three planes: flexion-extension, lateral bending and axial rotation—all of which can be compromised by high pressures under the saddle (see fig 7). 

Studies in sport horses have shown that saddles which restrict this zone around T13 restrict muscle development and negatively influence gait. This effect is amplified in a racehorse because they train at higher speeds, and faster speeds are associated with higher forces and pressures. In addition, gallop requires significant flexion and extension of the horse’s spine; and if this is compromised by saddle design, it seems logical there will be an effect on the locomotor apparatus.

Tree length

In addition, half-tree and full-tree saddles were shown to cause pressure where the end of the tree makes contact with the horse’s back during spinal extension at gallop. In the three-quarter-tree, high pressure peaks were seen every stride and either side of the spine, correlating with the horse’s gallop lead; this indicated that the saddle was unstable at speed (see fig 1).

Using a modified saddle design to achieve a more symmetrical pressure distribution, researchers saw a positive impact on spinal stability and back muscle activation. The hindlimb was shown to come under the galloping horse’s centre of mass, leading to increased hip flexion, stride length and power. A longer stride length means fewer strides are necessary to cover any given distance; and better stride efficiency brings benefits in terms of the horse’s training potential and susceptibility to injury (see compensatory strategy panel). 

Half-tree: High peak pressures consistent with the end of the tree

Three-quarter-tree: Peak pressure on one side of the back at a time, depending on the gallop lead  

Full-tree: Peak pressure was further back 

New design: The lowest peak pressures with a more uniform distribution

Improved hip flexion was recorded in the new saddle design (A) compared to a commonly used saddle (B)]

Pressure pad

The saddle pad acts as a dampening layer between the horse and the saddle, reducing pressures and absorbing forces. In a pilot study of thoroughbreds galloping at half speed over ground, a medical-grade foam saddle pad was shown to be superior at reducing pressure, significantly outperforming gel and polyfill pads. Preliminary findings show the forces were 75% lower, and peak pressures were 65% lower under the foam pad than those recorded under the gel pad. The polyfill pad reduced the forces and peak pressures by 25% and 44%, respectively, compared to the viscose gel pad. 

A pad with a midline ‘seam’ designed to follow the contour of the horse’s back and withers performed best, maintaining position and providing spinal clearance even at speed. Flat pads without any shaping or a central seam were observed to slip down against the spine as the horse moved, even when the pads were pulled up into the saddle channel before setting off. The pressure associated with a pad drawing down on the spine under the saddle will lead to increased muscle tension, reduce elasticity of the back and could potentially alter gait. Relieving pressure at this location improves posture, movement and propulsion.

It might be assumed that using multiple pads under an exercise saddle would improve spinal clearance or comfort. However, based on studies, this is not the case. In contrast, it can lead to saddle instability, which has the potential to encourage the jockey to overtighten the girth in an attempt to keep the saddle still. The added bulk puts a feeling of distance between the horse and rider, compromising the close-contact feel and balance all jockeys strive to achieve. 

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THIS ARTICLE FIRST APPEARED IN - NORTH AMERICAN TRAINER - ISSUE 29