Posted by on 13. June 2018

Fairy tales of biomechanics of the spine frequently quoted

I would like to get rid of some of the misinformation I heard during lectures on the biomechanics of the horse’s spine.

  • Horses must not let their necks fall while riding, the nuts and bolts of riding are the work in collection. In a lowered head-neck posture, only the lower neck muscles would work anyway.

  • The spine cannot bend at all (flexion), but can only carry out a rotational movement.

In general, one should know that the muscles do not only work in contraction. And this working principle must be kept in mind, no matter what movement is analyzed.
Musculature has not only the 2 states contraction and relaxation. The term relaxation does not mean that a horse with drooping ears and slobbering limbs shuffles through the track.

A muscle that decontracts returns to its basic tone (tonus = isometric muscle work see below) and that is not zero. But a state in which the muscle and its synergists together hold the joint in a zero position against the force of the antagonists.
This means that the joint is exactly in the middle of its physiological range of motion. Whether the horse has the tension 3 or 8 in its agonists and antagonists depends on the level of training and education.

    The only important thing is
    Tension of all agonists = Tension of all antagonists


    Tension left side of body = Tension right side of body

This creates balance as a basic prerequisite for the rhythm in gaits.

If this equilibrium is not given, we speak of an osteopathic lesion or dysfunction

But you can give day-long lectures on tact, suppleness and contact to bit. I also think that this is much more important than dealing with collection. Collection comes of its own accord when a horse is trained according to the scala of education and certain basic biomechanic rules are known and observed.

So let’s take a look at the

    Muscular function:

      1. concentric work i.e. the muscle tension changes and the muscle shortens (positively dynamic)
      2. isometric work i.e. muscle tension changes and muscle length remains constant
      3. eccentric work i.e. muscle tension changes and muscle lengthens (negative dynamic, heaviest form of work)

Flexion and extension of the spine and its benefits for horse and rider

    Part 1: Neck posture

      In a correct head-neck position, the under-neck muscles work in concentric work – not with regard to lowering of the head – but because parts of the under-neck muscles are responsible for lifting the front limb.
      That’s why they work concentrically. Otherwise they work isometrically for the most time.

      The upper neck muscles especially the M. longissimus colli but also the long head extensors work eccentrically. So they are not limp or relaxed, as is sometimes so misrepresented.
      The dorsal neck and back muscles are slack only in sedation, then the head hangs, as far as the neckbands permit it, namely until briefly over the ground. However, this does not mean that horses that stretch to just above the ground when awake have no tone in the upper neck muscles.
      In a correct stretching posture, the upper neck muscles work in so far as they carry the head of the horse against gravity. Eccentric and with highest possible force.

      And damage to the neckbands is not due to the horses dropping their necks particularly low. But therefore that they are ridden with the head behind the vertical (no stretch in the throatlatch). This overstretches and damages the head extension and the neckbands.

    To assess how hard concentric or eccentric muscle work really is, you can simply test what is more strenuous:

      Take 5 kg (2 kg should be enough for delicate persons) in your right hand and hold your arm in a 90° bend.
      Slowly bend the arm with the weight and stretch it back up to 90° and test how hard it is for you.
      And then you can stretch your arm to fast 180° and bends back to 90°. Always hold against the weight and make the movement nice and slow.
      Just try how many repetitions you make in the bending and how many you make in the stretching.

This would clarify whether the upper neck muscles have to work in the stretching posture.
Yes, more than the lower neck muscles.

And the question how high or low, short or long the horse should carry his neck is answered from

    1. The training level of the respective horse

      The neck of the young horse, lowered and stretched forward, is nothing more than an aid with which the horse seeks its balance (the neck as a balancing pole) and with which it initially tries to carry the rider’s weight through the neckband and not through the muscles. Muscular can fatigue. Not the neckband.
      The higher the neck is worn, the less the neckband carries. Horses with little developed supporting musculature fatigue fast in this position.
      The higher the neck is worn, the higher the horse’s centre of gravity is. And it is all the more difficult for an unbalanced horse to find his balance.
      The shorter the neck is made, the less it helps the horse as a balancing pole: this makes it more difficult for the horse to find balance again.
      All this has nothing to do with what I believe, but is simple physics.
      You probably won’t find a single tightrope walker holding a toothpick high above his head with his arms outstretched.

    2. Anatomy of the horse

      Horses with a powerful muscled, short trunk can be trained faster and have to carry out less work in the back muscles. That’s why you can collect them faster than a thoroughbred rectangular horse. These horses are probably also faster in balance. However, they also develop less momentum.

    3. The presence of osteopathic and orthopedic problems

      Horses with osteopathic lesions or even bony changes in the area of the cervical vertebrae near the thorax are not particularly grateful if you straighten them in the neck. It is important to know that the flexion of the spine facilitates the lateral inclination and rotation of the individual vertebrae. If the horse’s mobility is restricted by arthrosis or muscle tension and ligament lesions, it makes sense to facilitate its movement by flexion.
      This does not only apply to horses with problems in the cervical or back spine. But also for the healthy horse.
      Once the spine is in flexion, you can bend your horses more easily.

And just because the horse carries its head low, it does not have to fall on the forehand.

Whoever believes that has not understood the term “relative erection”.

Collection has nothing to do with the height of the head, but with the ability of the horse to lift and carry itself between its forelegs.

Nor has collection something to do with the head held up or down (always assuming the throatlatch is in a stretched posture and the horse stretches to the bit).
Really well-trained horses manage to keep their head low above the ground while remaining in a stretched position and still clearly lifting their withers between their front legs.

Waiki training lunge, Andrea Bethge, playful.piaffe

Of course, the work in the hindquarters changes (angulation in the hip joint becomes smaller), which simply has to be taken into account.

Biomechnics of the spinal column part II will follow soon. The focus here is on the biomechanics of the thoracic and lumbar spine.