Things worth knowing about the horse’s back, the rider and the saddle
Long before man discovered that the horse‘s back could be used to carry loads, this part of the horses body had to fulfil a number of important functions. Even if we today mistakenly assume that the back was made for riding, it is actually a subordinate function. The back is unquestionably central to the quality of the horse’s movement and, apart from the mouth, is one of the most sensitive parts of the animal’s body. Nevertheless, it bears the brunt of the burden and is put under most stress when the horse is ridden.
But what actually happens to the back of the horse when it is ridden and what is important for us when building the right saddle?
1. Structure of the back
We understand the horse’s back to mean the thoracic and lumbar vertebrae, along with the associated bones, joints, ligaments, muscles, nerves and tendons. It is closely linked to other parts of the body, such as the head and neck, the chest and abdominal wall, in addition to the shoulder and pelvic limbs. It also consists of a large number of different tissue elements that are closely linked to each other, but should be addressed separately. It is particularly evident in the back how the various structures, such as bones, muscles, ligaments, tendons and nerves interact with each other.
2. Functions of the back
Of the many important jobs it has to perform, a few are mentioned below:
- protection of the spinal cord
- protection for the heart and lungs
- support for the internal organs
- freedom of movement of the limbs
3. The bone structure of the skeleton
The thoracic and lumbar vertebrae make up the bone structure of the horse’s back. Compared with the cervical vertebrae, the thoracic and lumbar vertebrae have little curve and, due to their special structure, allow very little movement.
The individual vertebrae have a growth plate at the front the rear end to provide linear growth. The spine of a horse will continue to grow until quite late, with the last growth plates of the spine not fusing until around the age of six. In addition, the dorsal spinous processes of the thoracic vertebrae have their own centres of ossification, which do not complete their growth until the horse is over 10 years of age.
The horse‘s spine can be likened to a curved chain made up of differently shaped vertebrae. It is composed of 7 cervical vertebrae, 18 thoracic vertebrae, 6 lumbar vertebrae, 5 sacral and 18 to 21 caudal vertebrae. The back can be seen as a bridge construction, with the limbs serving as supporting pillars. When viewed from the side, we should really speak of a spinal bridge rather than a spinal column.
As a result of this structure, the horse‘s back can easily carry very heavy loads.
In 1892, the Swiss veterinary surgeon Erwin Zschokke was one of the first Europeans to take precise measurements of movements of the horse’s spine. He discovered that the dorsal spinous processes, together with the attached ligamentum supraspinale (supraspinous ligament), are important for the stability of the spine. He also observed that the average lowering of the back under loads weighing from 50 to 80 kg amounted to only 4 cm with intact dorsal spinous processes. He was the first person to describe the change in position of the dorsal spinous processes with respect to the head and neck position.
There are extensions on the thoracic, lumbar and sacral vertebrae projecting upwards, so-called dorsal spinous processes. They lean backwards towards the horse’s tail as far as the 15th thoracic vertebra. The 16th thoracic vertebra is upright, after which all the dorsal spinous processes are inclined towards the horse’s head. The 18 thoracic vertebrae provide lateral attachment on each side for the 8 pairs of supporting or true ribs and the 10 pairs of respiratory ribs.Together with the sternum, to which the ribs are attached via the costal cartilages, they form a stable, closed rib cage.
This protects the internal organs from injury, on the one hand, while at the same time giving the locomotor apparatus of the horse the stability required to support the rider’s weight.
Directions of movement:
Today, the four directions of movement are described as follows:
- Dorsiflexion – hollowing of the back
- Ventroflexion – arching of the back
- Lateral flexion – bending to one side
- Torsion – twisting
The greatest amount of lateral bending occurs when the horse is walking, while most arching and hollowing of the spine occurs when trotting. At walk and trot, we can measure a difference in the level of the spine of 4 to 5 cm, whereas at canter/gallop we measure a difference in level of only 3 cm.
From a practical viewpoint, the sternum also makes it possible for us to attach a girth in the first place, which enables us to ride horses.
4. The back muscles
Put simply, we can break down the muscles on the back into true and connecting back muscles. We also distinguish between short back muscles and long back muscles.
An important back muscle is without doubt the long back muscle, musculus longissimus dorsi, which stretches along the length of the spine. Its purpose is to cover the triangular section between the dorsal and the lateral spinous processes and also to extend over the dorsal spinous processes.
In addition to the muscles lying on top of the spine, other muscles are needed that run under the spine and also have to be trained just like the lumbar muscles.
With respect to the muscles in the trunk and neck, a distinction is made between the upper, middle and lower muscle groups. The upper muscle group includes the long back muscle and the splenius muscle, the middle group includes the long neck muscle and the inner lumbar muscles, and the lower includes the straight abdominal muscle.
As a result of repeatedly engaging its hindquarters, the horse is forced to round its back. This is also known as bascule.
The opposite would be a sagging back or swayback. Close examination of the vertebrae reveals that the dorsal spinous processes between the 14th and 16th thoracic vertebrae are almost upright, i.e. this is where the centre of arching of the spine lies and thus the centre of stability.
Dupaty de Clam, musketeer to the King of France, wrote in 1769 in the last chapter of his book on the art of riding on the importance of the centre of gravity of the rider and the horse, and of the effect each one had on the other.
Fauques in 1982 was the first person to measure the distance between the dorsal spinous processes on a living horse in motion with respect to the position of the head. He discovered that the distance between the dorsal spinal processes was not dependent solely on the gait, but on the position of the head.
The lowest point of the saddle must lie in this area, therefore, as even a fully grown horse would not be able to endure the stress caused by the weight of an incorrectly positioned rider for an extended period of time.
Let is now take a look at the spinal column of the rider. All we have to do is make sure that the posture we adopt in the saddle is aligned with our biomechanically predetermined plumb line, i.e. in line with the natural curves of our spine in order to bring the plumb line of the horse in harmony with our own plumb line.
- The plumb line must be dropped from the ear, go through the shoulder and hip down to the ankle.
- Correct riding posture means sitting upright, placing the weight evenly over the left and right seat bone.
- Sitting upright does not mean raising the pelvis, but rather letting the pelvis lean forward.
- Good balance means having unrestricted movement of the joints and supple muscles to maintain equilibrium in motion.
It is assumed that the kissing spines syndrome is the result of repeated forced, not physiological, lowering of the back. The declining tensile strength of the back muscles and restricted head movement, along with the associated decline in the tension of the spine, may be possible causes.
A saddle is used to make riding more comfortable and safer for the rider and the same time to protect the animal’s back. The saddle that fits both the horse and the rider well will help us to improve our riding, it will place us where the horse would place us if there were no saddle, which would be just behind the withers.
The saddle must fit the horse perfectly, which means it must provide optimum freedom of movement for the shoulder blades, the withers and the curvature of the spine.
From the saddler‘s viewpoint, the withers is one of the most important parts of the horse’s back. This is where the saddle is placed and, when the rider’s weight is added, is the position on the back where the total amount of extra weight has to be supported. It should be noted that a horse at rest already supports 55 per cent of its weight on its forelegs and 45 per cent on its hind legs.
The horse’s natural balance point, its centre of gravity, is roughly at the level of the sternum, below the middle of the belly. In addition, the thick, approximately 3cm wide back edge of the shoulder blade lies just under the withers. This saddler must also attach considerable importance to this point as well, because this is the where movement of the shoulder blade occurs.
In well-trained horses in particular, the trapezius muscles are well developed behind the shoulder. The trapezius muscles extend upwards, branching out into the long back muscles, with the rib muscles and back muscles intertwine.
The saddle must permit unrestricted movement of the shoulders. To make this possible, the panels must open on each side at the front. The movement of the shoulders is restricted by the design of conventional panels, as the shoulder comes up against the front edge of the panels with each movement. Mistakenly, many saddles are heavily padded and narrow in this area, instead of modifying the saddle tree and gullet plate and leaving the panel open.
The so-called front point strap can increase tension in the shoulder by pulling too tightly on the saddle at the front of the saddle tree. This leads to tenseness of the muscles, which, due to the interweaving of the muscles, can extend as far back as the medial and superficial gluteal muscles. This can result in a “cold back“, problems getting the horse on the bit, fear of being mounted, unwillingness to work, flinching when being groomed and lots more.
The shape of the saddle panels must also follow the anatomy of the horse’s back as closely as possible. Considerable back problems can occur due to the use of narrow panels especially as a result of the intertwining of the rib muscles with the back muscles. The ideal saddle panel should overlap the rib and back muscles at the point where they meet. If the panels are too narrow, they will press the long back muscle upwards against the vertebrae and the dorsal spinous processes and press the rib muscles downwards..
As we can see, a saddle is not only required to accommodate an elastic gait and long stride, it should actually encourage them. This has resulted in a number of fundamental rules of saddle design and construction that are closely adhered to by professional craftsmen in every SOMMER saddle that leaves our premises.