Fitting the Asymmetrical Horse: A Guide to Shimming and Panel Adjustments

Does your saddle consistently slip to one side, no matter how carefully you place it? Do you find yourself constantly shifting your weight to stay centered?

This common and frustrating problem leads many riders to blame the saddle, the pad, or even their own riding skills. But what if the answer lies deeper—in your horse’s own body?

The truth is, the vast majority of horses, just like humans, are not perfectly symmetrical. This natural unevenness is one of the most common yet overlooked factors in saddle fitting challenges. Understanding this is the first step toward creating a more comfortable, balanced, and harmonious partnership with your horse.

The Surprising Truth: Most Horses Aren’t Symmetrical

If you’ve ever noticed one of your horse’s shoulders is larger or more developed than the other, you’re not alone—you’re observing a widespread phenomenon. Research shows just how common this is: one study found that a staggering 74% of horses exhibited asymmetry in the longissimus dorsi, the large muscles running along either side of the spine.

This asymmetry isn’t a flaw; it’s a characteristic that can stem from a variety of factors:

• Natural ‘Handedness’: Just as we are right- or left-handed, horses often have a dominant side.
• Training and Development: Young horses or those in retraining are constantly building and changing muscle.
• Past Injuries: Compensation for an old injury can lead to uneven muscle development.
• Rider Influence: An unbalanced rider can inadvertently encourage a horse to develop asymmetrically over time.

The most common pattern is a more developed left side, but the key takeaway is this: treating an asymmetrical horse as if it were symmetrical is a recipe for poor saddle fit, discomfort, and performance problems.

How to Spot Asymmetry in Your Horse

You don’t need to be a veterinarian to start identifying potential asymmetries. A few simple, hands-on checks can give you valuable clues.

The View From Behind

Stand your horse on level ground and, from a safe position behind them, look over their back toward their withers. Do the muscles on either side of the withers look like mirror images? Or does one side appear fuller, higher, or more developed? Pay close attention to the area just behind the shoulder blades, as this is often where differences are most visible.

The Feel Test

With your horse standing squarely, run your hands down both sides of their spine from the withers to the croup, applying gentle, even pressure. Note any differences in muscle tone. Does one side feel harder and more developed, while the other feels softer or hollow? A hollow area often indicates that the saddle is bridging or putting excessive pressure elsewhere, causing the muscle to atrophy or waste away.

Under-Saddle Clues

The most obvious sign is a saddle that consistently slips to one side, usually toward the less-muscled or lower side. Other signs include:

• Your horse resisting a bend in one direction.
• Difficulty picking up a specific canter lead.
• Needing to adjust your stirrups unevenly to feel balanced.
• Uneven sweat marks after a ride.

The Vicious Cycle: Horse, Rider, and Saddle

This asymmetry creates a challenging cycle. An uneven horse causes the saddle to tilt. To compensate, the rider becomes crooked—often collapsing a hip or leaning to one side.

This crooked position then puts uneven pressure on the horse’s back, reinforcing the very asymmetry that created the problem in the first place. Breaking this cycle is crucial for the long-term health and soundness of both horse and rider. The solution lies not in forcing a standard saddle onto an uneven back, but in using an adaptable saddle system that creates a level platform for the rider while giving the horse freedom to move and redevelop its muscles correctly.

Corrective Solutions: Shimming vs. Adjustable Panels

Once you’ve identified an asymmetry, the goal is to compensate for the difference temporarily. This provides stability for the rider and relieves pressure on the horse, allowing the weaker muscles to rebuild. The two most common methods are shimming and professional panel adjustments.

What Are Shims?

Shims are inserts, typically made of foam or felt, that are placed into the pockets of a special corrective saddle pad. For a horse with a hollow or less-developed right side, you would place a shim in the right pocket of the pad to fill that gap and level the saddle.

Shims are an excellent temporary solution, especially for horses undergoing significant muscular change, such as those in rehabilitation or young horses just starting training. They can be easily added or removed as the horse’s shape evolves. The main downside is that shims can sometimes shift or create new pressure points if not used correctly. While they are a useful management tool, they work outside the saddle’s core structure.

The Power of Adjustable Panels

A more integrated and stable solution is a saddle with flocking panels that can be professionally adjusted. Saddles with wool-flocked panels allow a qualified saddle fitter to add or remove flocking from specific areas inside the saddle itself. This process is akin to creating a custom-molded orthotic for your horse’s back.

At Iberosattel, this principle is central to our design philosophy. We use fully adjustable wool-flocked panels because it allows the saddle to become a dynamic tool for the horse’s development. A fitter can precisely adjust the panels to support a weaker side, lifting the saddle into a balanced position. This creates a perfect, stable platform for the rider without requiring an external pad or shim.

The beauty of this approach is its adaptability. As the horse’s muscles develop and the back becomes more even, the flocking can be removed, allowing the saddle to adapt perfectly to the horse’s new, more symmetrical shape. The foundation of any adaptable saddle is understanding how to choose the right saddle for your horse and its unique conformation. This challenge is often magnified in certain body types, making a thoughtful approach to saddle fit for short-backed horses especially important. This level of customization, often paired with an adjustable gullet system, ensures the saddle can evolve with your horse over a lifetime.

A Note on Professional Guidance

While identifying asymmetry is a great first step, implementing a solution should always involve a professional. A qualified saddle fitter can accurately assess the extent of the asymmetry and recommend the best course of action.

They can ensure shims are placed correctly or adjust the flocking in your saddle with precision, preventing unintended pressure points and ensuring the solution is truly helping—not hindering—your horse. The ultimate goal is to create enough comfort and balance for the horse’s musculature to even out over time, allowing the corrective adjustments to be gradually removed.

Frequently Asked Questions (FAQ)

Can a poorly fitting saddle cause asymmetry?

Absolutely. A saddle that is too narrow or ‘pinches’ can cause muscle atrophy on one or both sides. Likewise, a saddle that constantly slides to one side forces the horse to compensate, leading to uneven muscle development over time.

Will my horse ever be perfectly symmetrical?

Probably not, and that’s okay! Just like humans, very few horses are perfectly ambidextrous. The goal isn’t perfect mathematical symmetry, but functional balance—where the horse can move freely, comfortably, and evenly in both directions without being restricted by tack.

How often should I have my saddle fit checked for an asymmetrical horse?

If you are using corrective measures while your horse is in active training, it’s wise to have the fit checked more frequently—perhaps every three to six months. As your horse’s muscles change, the saddle will need to be adjusted accordingly.

Is one shoulder always bigger than the other?

It is very common for horses to have one shoulder that is larger and more developed than the other, often the left. This can be due to their inherent ‘handedness’ or patterns developed during training. A well-designed saddle accounts for this by allowing the shoulders complete freedom of movement.

Your Path to a More Balanced Partnership

Recognizing and addressing asymmetry is one of the most profound things you can do for your horse’s comfort and performance. It transforms the saddle from a simple piece of equipment into a therapeutic tool that supports your horse’s physical development.

By paying attention to the subtle clues your horse gives you and working with a professional to find a balanced solution, you aren’t just fixing a slipping saddle—you’re building a stronger, healthier, and more harmonious connection.