Why is it important to understand the biomechanical function of the horse? If we do not understand how a horse works, then we cannot fully understand just what it is we are asking for of our horses under saddle. I hope that this introduction to biomechanics opens the door to a better understanding of our equine friends, and possibly a desire to dive deeper!
First Thing’s First
A horse is not made to carry weight, A horse Is built to suspend their weight! Think of your horse more so as a suspension bridge, with many mechanisms in place in order for it to function optimally. There is no one aspect of the horse’s physiology that is more important than others. They all need to function harmoniously for the horse to lift and suspend weight.
When we speak of a horse working correctly, we often hear trainers and instructors say that the horse is working over the back, or using the hind end correctly. Both of these statements are not wrong, but I feel that they do not help in painting the bigger picture. In order for the horse to work correctly “over the back” much more than just the back needs to be functioning collectively. The Longissimus Dorsi muscles are the long back muscles that attach at the base of the wither/scapula and run parallel to the spine. These large muscles are not solely responsible for the lift of the back and activation of the hind end, though are important to develop. There are also the trapezius muscles, Splenius and Serratus Ventralis of the neck that work collectively to lift the horse from the neck, withers and base of the withers. This muscle group, along with the Thoracic Sling, work collectively to lift the withers, back and chest. Without this engagement, we cannot help the horse to truly work “over the back” and engage the hind end. This lifting of the front end and back allows for what we call “uphill” movement, and “lightness” of the front end. With conditioning, the horse will begin to strengthen these muscles and be capable of carrying more weight on the hind end. With a consistently light front end, the excess weight of the rider will not cause the forehand to be heavy and the horse will be less reliant on the front limbs to hold itself up. The hind legs will also be able to come through with more fluidity and ease as the front limbs no longer restrict and inhibit movement.
The Thoracic Sling
This is a very important and crucial system that needs to be accounted for when developing the horse. What is it? This mechanism is responsible for holding the chest cavity in place! Horses do not have a collarbone that stabilizes their chest cavity, therefore they rely on this mechanism of ligaments, fascia and muscle to stabilize their chest cavity.
Why is it so important? When we speak of asking the horse to use their back or work through/over their back, this mechanism needs to be activated. The thoracic sling is what aids in lifting the back and withers, and activating their core. It is just about impossible for a horse to become light on their forehand, lift their back and come through and under with their hind end when the thoracic sling is dropped and inactive.
And so, in training and working our horses it is much more than just getting a horse to have an activated and working hind end, there is an entire system at work that needs to come alive in the horse!
This drawing shows the internal difference between a “dropped” and “lifted” chest cavity via activation of the thoracic sling mechanism.
How do we go about asking the horse to lift the chest? Often times, many horses are used to being ridden “hollow” with a concaved spine and dropped chest cavity. Sometimes they will need a bit of outside help via body work. But there is a way to work through this change and teach the horse to lift through ground work and riding! But first and foremost we need to train our eye to be able to see the difference!
Below are some examples of a dropped mechanism and an active one:
Totilas is a prime example of a horse that has been ridden hollow in excess and resulted in serious injury and retirement at just 12 years old. The above image is a young Totilas ridden quite nicely in an extended trot as a 5 year old. The bottom image is Totilas being ridden in a Grand Prix test. Can you see the drop of his spine just behind the withers, causing the rider to “fall” deeper into his front end? In the top image the rider looks as if Totilas is lifting him up, allowing the rider to sit lightly and in a more balanced position. In the above image, Totilas in his entire form takes the shape of a suspension bridge, being convex from poll to tail. He is not consistently behind the vertical, and his limbs do not appear heavy as his body is working collectively. The bottom image is quite the opposite, with his body being concaved, heavy and over expressive limbs needing to work much harder, a braced and hyperflexed neck resulting in a horse being consistently behind the vertical. Just as a swinging bridge is concaved and the two points of connection allow for the mass in the center to hang, so is Totilas. His sacrum/hind end and withers and scapula are responsible for “holding up” the center mass. This is extremely painful and leads to a large array of physical ailments in the horse. Including but not limited to: Tendon and ligament injuries of the distal limbs, muscle atrophy, early onset arthritis, degradation and ossification of major joints, nerve damage, kissing spine, lordosis, ligament damage in the neck, tmj, overall regular soreness and a reactive horse.
This before and after image is of my personal horse Pharra, a 16hh arabian mare that I rescued close to 5 years ago. The top photo was taken just hours before the bottom one before a body work session. Due to injury, incorrect training and treatment, Pharra learned to brace and “protect” herself by dropping her chest cavity, keeping her muscles in her back, withers and neck tight and braced and constantly moving in a hollow frame. It was becoming difficult in her groundwork to continue further and so it was time to have her get regular body work to help us get over a plateau. This side view beautifully demonstrates how stuck she was and just how impossible it was for her to really lengthen her topline and become more elastic, which effected her just about everywhere! In the bottom image, we see how allowing the thoracic sling to lift her up immediately allowed for her to lengthen, stretch and allow the neck to drop! Since this body work session a year and a half ago, she has not reverted to the above image, but it also became more clear that her bracing was how she could tolerate a rider and so with helping her soften through regular body work and rebuild her “lifting” muscles and mechanism she is no longer rideable as it causes her too much pain. She stays in consistent ground work to help her maintain a level of comfort out in the pasture with her herd mates and physically looks the best she has ever been! The process will be never ending and a life long commitment to help her continue to get better, and it has been so rewarding to be able to help her in this way.
Where To Start!
To begin asking your horse to lift and develop self carriage (aka activation of the thoracic sling and lifting of the front end), we first need to establish suppleness through stretching. This can be done on the ground as well as under saddle. It is always best to introduce something new to your horse on the ground, especially when you are also wanting to develop your eye! Make your lunging and ground work count and start to introduce suppleness, relaxation and stretch. When the horse becomes more and more supple, they will wish to seek that and keep it as it feels much better than constant brace. This suppleness will extend from the jaw all the way to the hind end and it will seem as if every muscle and aspect of the horse is working effortlessly and collectively. In this the horse will develop more and more strength and over time will find no issue in having rhythm, balance and lightness in all 3 gaits!
Below, Caterina shows off her lovely developed stretch on the ground!
Once the horse seems to be in a good place with stretching and building suppleness on the ground and under saddle, you can begin to ask for full body engagement in transitions to really help activate the thoracic sling and get the back and withers to lift! In order to do so, we also must be sure that we are not getting in the horse’s way, whether it is on the ground or under saddle. We need to develop consistent contact with our horses through our seat as well as our hands. With the horse being relaxed, supple and accepting of aids and our hands, we begin to teach the horse to specifically lift and lighten one shoulder or the other. This will activate the muscles in the thoracic sling and strengthen them further!
As we continue, we can further develop the horse in a way that we can ask for more collection as the horse has developed an understanding of self carriage as well as the muscle development to sustain it through difficult and advanced movements such as piaffe, passage, canter pirouettes and tempe changes!
