While horses have an amazingly designed back, I will only attempt here to give a brief picture of how they work, in very simplified form. My aim is not to give an understanding of the function of each muscle, bone and joint, (not to mention fascia, nerves etc) but rather to provide a basic and simplified illustration of some of what is important in relation to riding a horse and maintaining its health, particularly in relation to the back.
The head and neck of the horse acts a bit like a pendulum, to help to balance the horse. The vertebrae in the neck of the horse are the cervical vertebrae and form a bit of a gentle S shape. The cervical vertebrae do not all run along the top of the neck. The junction between the cervical and thoracic vertebrae is hidden behind the scapula, or shoulder blade.
The hindquarter of the horse is the powerhouse, the motor, and this is where propulsion is created. Power generated through the action of the hindquarters is transferred through the pelvic structure, then through the spine and its surrounding structures to the front end of the horse.
The forequarter of the horse is responsible for carrying weight, absorbing impact and balancing and supporting the body. Most of the weight of the horse is carried by the forequarters, so there is where injury is most likely to occur when the horse is overworked.
The back of the horse is the bridge that connects the horses back end with the front end. This might sound very basic, but it is often ignored. Please remember that the back of a horse is like a bridge.
Some of the ribs are attached to the breastbone and help to support the chest, and the ribs further back are involved with breathing. Each rib connects to a thoracic vertebra. There is very little movement that can occur through the thoracic vertebrae as they are connected to the ribs.
The loins of the horse correspond to our lower back, and are formed by the lumbar vertebrae. These vertebrae are not connected to the ribs so they have more movement, but they cannot bear weight. The weakest point of the back is the thoracic lumbar junction, or TL joint, where the thoracic vertebrae meet the lumbar vertebrae. Yet it is often here that weight is placed via the saddle.
The sacral vertebrae are fused together to form the sacrum, and are connected to the pelvis structure through the sacro-iliac joints. The lumbo-sacral junction is the hinge joint between the lumbar and sacral vertebrae that allows the pelvis to tilt. The vertebrae that continue on into the tail are the caudal vertebrae.
The sacrum (the fused sacral vertebrae) transfers the thrust created by the hindquarter from the rump right along the back, creating forward movement. The back muscles are highly enervated; one of the back muscles has one nerve fibre for each muscle fibre! The energy produced by the hindquarter fires the nerves in sequence along the back, from the sacrum towards the head, much like running one’s fingers along the keys of a piano in sequence. The energy is thus transformed into movement. This movement travels from the sacrum right along the length of the back, through the base of the neck and up through the cervical vertebrae of the neck to the poll.
Manolo Mendez likes to compare the spine to a train, which is easy to picture as we know that each train carriage is solid and fixed, and just the joints in between can allow a little movement that flows along the whole train. At the canter the spine undulates up and down while at the trot it undulates side to side.
The spine and muscles in the back need to be allowed to, and encouraged to, undulate and swing in their natural movement so that the horse can develop good natural rhythm, impulsion and overall movement. The term back mover means a horse which has a relaxed and swinging back; a horse which has been taught to carry and balance the weight of tack and rider with a relaxed back.
You have probably quickly seen that for energy to be converted to movement through the back, the back must be allowed to move under the saddle. This then, that the back muscles are movement muscles and not weight carrying muscles, is one of the most important things we need to know as horse people. The back must be allowed to move freely for the horse to move freely. The strength of the back muscles is of much less importance than the activity of the back muscles; they must be used for movement, not for weight carrying.
So now we think of a young horse being ridden. The horse is not designed to carry the weight of the tack and the rider, and will instinctively tense its back muscles in an effort to carry and balance the unfamiliar weight. As this tensing of the back is tiring and causes pain, the young horse may then drop the back in an effort to relieve the strain and pain. A cycle can quickly develop of tensing the back to carry the weight and find balance, followed by dropping the back to relieve the pain. Neither is beneficial.
Once the back has become tensed, the propulsive energy from the hindquarter is not able to be correctly transferred through the back, as the long back muscles are too tight, maybe even locked. Yet the back muscles are also connected to the rump muscles through the fascia, to the ribs, and to the forequarters. So a tense back means that the muscles in the hindquarter cannot function properly and the hindleg stride is adversely affected; breathing is affected; and the muscles in the forehand are also unable to function properly so there is restriction through the shoulder and the front stride is affected. Not to forget, the pelvis is negatively affected. Tension in the back also exerts additional strain on ligaments and tendons throughout the trunk of the horse which then stiffens, thus increasing the load on the legs, which can then cause damage in the legs.
So if a young horse under saddle naturally uses its back and thus its body in an incorrect way that leads to pain and poor function and movement, we must teach the horse to use itself differently, yes? It is generally assumed that as a horse is a big strong fast and powerful animal, it can carry us no worries, and we certainly don’t need to teach it how to do that. However, the truth is that if we leave it all up to the horse to battle its way through this unnatural situation, it will suffer tension, discomfort and pain, and will suffer damage that will affect it in the long term. It is very rare that I work on a horse that is not suffering from basic postural and movement problems caused by the horse trying unsuccessfully on its own, without assistance, to manage having a rider aboard.
Yet with some effort on our behalf combined with some simple training techniques we can help our horses to carry and balance our weight in healthy ways that take into account how the horses body works. Next time I will briefly discuss how the posture of the head and neck can have a profound impact on the health of the back, and thus the whole horse.