Part II

(E-mails after e-mails!  We have been submerged by riders, trainers, and horse owners recognizing ghosts around them. The surprising abundance of responses gave birth to the idea that it would be productive to compare, one by one, the empty theories that are lurking on the web with actual knowledge of the equine physiology. The purpose is not to educate the ghosts, since they already know it all, but instead to unravel the danger of opinions and theories unrelated to the horse’s physiology.)

I was cited in a reference of a strange theory and entered a discussion about the telescopic action of the neck. I pointed out that even as a metaphor, the expression “telescopic action” was inappropriate since there is no telescopic action at all in the neck. Rapidly the exchanges turned into useless diatribes, where the opponents were changing statements from one e-mail to the other. What became scarily obvious was that they had a very distorted understanding of the way cervical muscles, ligaments and vertebrae operate.

Even simple looks at the neck structure quickly dismiss the telescoping theory. The cervical vertebrae are always aligned in an S shape. The S shape is evidently deformable allowing different neck positions. As early as 1915, Virchow observed that at the most the lower loop of the cervical S can be practically straight. “The cervical vertebral column can be stretched only so far that the vertebrae are lying in a straight line.”  Three decades later, E. J. Slijper made the same observation adding that the cervical vertebrae were aligned in straight line to allow grazing but never flexed in the opposite direction.  The Dutch scientist also pointed out that in order to reach the grass, the horse also separates the front legs.

The same observation was made in recent studies about the nuchal ligament. The nuchal ligament is attached on the fourth thoracic vertebra at one end and the cervical vertebrae and the skull at the other end. The general consensus is that the nuchal ligament is holding the neck in an alert position and yet is elastic enough to allow grazing. In reality, the nuchal ligament is not under tension when the neck is in a frame such as the one demanded at FEI level, and does not have enough elastic compliance to allow grazing. The horse compensates the limited elasticity of the nuchal ligament by separating the forelegs for grazing. The real function of the nuchal ligament is dynamic. The ligament replaces 55% of the work of the neck muscles at the walk and between 34 to 36% at the trot and canter. The horse lowers the neck after work in order to use the elastic compliance of the nuchal ligament and therefore ease the work of his upper neck muscles.

The muscular work does not pull the neck out of the shoulders as suggested in the telescopic rhetoric. Instead, upper and lower neck muscles are mainly focused on flexing or straightening, bending laterally, as well as lifting or lowering the neck. The main neck muscles involved in the lowering of the neck are the splenius and the semi spinalis capitis.  The semispinalis capitis muscle does have a tendon in the middle and this tendon elongates as the neck lowers. The work of the muscle cells is complex but more in the sense that within the same muscle, some muscle fibers are working concentric while other are working in isometric hold.

Muscle cells working in isometric hold can change their work into eccentric contraction when an outside element such as lowering of the neck is stimulating elongation. Eccentric contractions are extremely powerful. In his study R. C. Payne refers to eccentric contraction as being capable to absorb 15 times more energy than concentric contraction. In another study, Karen Gellman say that the power of the cell's contraction almost double. The author induces then an interesting thought. Muscles in isometric hold can only elongate 1 to 2% of their neutral length. Gellman regards the power of eccentric contractions as a protection mechanism preventing the muscles cells from becoming ripped by excessive elongation.

The results of scientific studies are directly influenced by the specific angle of the investigative technique. If the purpose of studying a study is to better train the horse, one needs to read the whole procedure, including the material and methods used for the experiment. The ghosts are only reading the first lines until they find a word or a line fitting their opinion. They then credit their opinion as “scientifically demonstrated.” Tom Gilovitch (psychologist) explains the phenomenon. “When we want to believe a proposition, we ask, ‘Can I believe it?’ – and we look only for evidence that the proposition might be true. If we find a single piece of evidence, then we are done. We stop. We have a reason we can trot out to support our belief.”

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Eccentric contraction is often referred to as active stretching. However this is not the stretching suggesting compliant elongation of the whole muscle. Instead, active stretching is a form of muscular contraction where the muscles greatly increase their power. A very simple question permits to shift from utopia to reality. The head and neck weight approximately 10% of the horse’s body mass. The burden of the head is aggravated by the length of the lever arm, which is the neck. Upper neck muscles and ligaments are working to resist gravity, which is pulling the neck onto the ground. Instead of thinking about a lowering of the neck pulling on the back muscles and therefore stretching the back muscles, one needs to think about back and extrinsic muscles of the forelegs resisting the force of gravity which is pulling the horse head and neck down to earth.

The second point contradicting theories of muscle elongation and increased range of motion is that the primary function of the back muscles is precisely to protect the throracolumbar spine from an amplitude of movements that would exceed the thoracolumbar spine’s possible range of motion. Efficiency is not achieved through greater range of motion but rather through better orchestration of numerous and minuscule muscles contraction and compensatory contractions.

The feeling of roundness and lift that one feels in association with a longer neck posture has been explained through different perspectives. For instance, Jean Marie Denoix introduces in 1999 a very interesting concept referred to as Instant Center of Rotation. Denoix discovered that when the neck is lowered, the center of rotation, which is a theoretical point around which one vertebra is turning around the other, is moving down and forward toward the intervertebral disk. Such displacement of the center of rotation tends to ease the stresses induced on the lower part of the intervertebral disk. The study does not speak of  how long or low the neck is placed,but  it would be rational to think that the horse would by himself adopt the neck posture which is gives greater ease in its vertebral column mechanism.

At the point of today’s knowledge, there are great disadvantages in forcing the horse into a given neck position. According to the horse’s morphology and muscular development, the neck position enhancing the horse’s vertebral column mechanism is proper to each individual horse. Imposing an artificial neck posture is forcing the horse to compensations that are likely to disturb the horse’s biological mechanism at many levels.

Saturday June 11, Immersion II, which will be organized at our place in Georgia will focus on the understanding and the practical application of the most recent research studies about longer neck posture. The event will be a three day event. In response to popular demands, Friday June 10 will be a repeat of Immersion I which is about quality of the gaits and the work in hand. Saturday June 11 will be about the practical application of the most advanced scientific discoveries related to the horse’s neck posture. Sunday June 12 will be Introduction, Explanation and Demonstration of the fact that lateral bending is always coupled with a movement of transversal rotation. Everyone is welcome. We can even invite the ghosts. They will not come anyway; they already know all.

Jean Luc Cornille

 

For price and itinerary of Immersion program email helyn@scienceofmotion.com

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