Let’s Talk Biomechanics: Horse Skeleton

Let’s Talk Biomechanics: Horse Skeleton

The horse’s skeleton is made up of bones that form a strong support for the muscles and provide movement. It includes:

• skull bones;
• vertebrae that form the spinal column;
• ribs;
• breast bone – the sternum, to which 8 pairs of ribs are attached;
• bones of the fore and hind limbs.

It is difficult to find words to describe in detail what happens when more than 200 bones of a horse, 700 of its skeletal muscles begin to move, and how fascia, tendons, ligaments, neurotransmitters, hormones and other elements of its body are connected to this work. A map is not a territory, it always simplifies a complex world and gives us a limited view of reality.

In order to optimize the training of a horse, to understand the complex multidimensional reality of the organism of this animal in all its dynamics, it is necessary to study the map of the horse’s skeleton. Let’s start with the video:

Let’s talk more about the bones and joints of the horse’s limbs, then about the spine and associated ribs, sternum and skull.

Front and back legs

The fragile front legs of a horse support about 3/5 of its weight – this is called natural balance (balance) and is one of the reasons that in most cases it is the front legs that suffer from lameness, and especially the most “supporting” front leg.

That’s why we work on straightness – first we equalize the amount of weight that is on all four legs (the so-called horizontal balance), so that each leg carries 25% of the weight, and then we transfer the weight to the back, to the flexible hind limbs.

This artificial “riding” balance, in which 3/5 of the horse’s body weight is transferred to its hindquarters, relieves the fragile front legs and allows the horse to carry the rider’s weight without harming it.

To achieve this artificial balance, we need to stretch and strengthen the horse’s hind legs. There are seven joints in the hind legs, which help during movement and make the hind legs flexible and powerful:

1. The sacroiliac joint, which connects the spine to the hind limb.

2. Hip joint.

3. Knee joint.

4. Hock joint.

5. Putovy joint, metacarpophalangeal joint.

6. Putovy joint, proximal interphalangeal joint.

7. Coronary joint, hoof joint.

A joint is a movable connection between two bones and provides movement in response to muscle contraction and lengthening. The seven joints make the limb look like a spring and allow it to develop its bearing potential.

Through the sacroiliac joints, the energy that is formed from the back is transferred through the spine forward. The bones of the forelegs are shorter and straighter than those of the hind legs and have only three “spring” joints (pink dots) that absorb and absorb impact force, making the forelimbs quite fragile.

To develop the carrying potential of the hind legs, the six keys of Straightness Work will help you (Key number 4 – flexion of the inside hind leg; Key number 5 – flexion of the outside hind leg and Key number 6 – flexion of both hind legs).

But in order to get to keys #4, #5 and #6, we need to first access the first three keys, and we do this by working on the horse’s spine.

Spine

The spine is the part of the skeleton that forms the connection between the fore and hind limbs of the horse (except for the neck and tail parts of the spine).

The spine plays an important role in movement because in most Straightness Work exercises, such as circles and lateral movements, we want our horse to move with the proper level of LFS as a result of the first three Straightness Work keys:

Key 1. – L – Lateral bending – Lateral bending.

Key 2. – F – Forward down – Forward and down.

Key 3. – S – Stepping under – The back leg steps under the center of gravity.

When working on LFS, the spine will automatically flex, flex, and rotate:

The movements of the spine can be described in three dimensions by setting three axes: x, y, z.

Depending on their location, the spine will move in three different directions:

X – elongation / compression;

Y – rotation;

Z – lateral bend.

All three of these types of movement—lengthening/compression, rotation, and lateral bending—occur in every part of the spine.

semantic difference

There is a semantic difference between lateral flexion in a sectional measurement of the spine and lateral flexion in the whole body:

1. Lateral bend in the spine is a measurement of the spine. This is the physical ability of the horse to bend more or less in certain areas of the spine.

2. The side bend of the body refers to the whole body. This is a general collective term that we use in Straightness Work to describe everything that happens throughout the horse’s body (muscles, legs, spine, contraction, rotation, flexion) that enables the horse to bend in a circular arc in both directions and allows her body to perform lateral movements. This “side bend” is a metaphor, a figure of speech, because many factors create the illusion of a side bend of the body.

As a result, when people start arguing about lateral flexion, this semantic discussion begins. The metaphor itself arose in the course of history, so let’s dive into the past a bit:

History of “bending”

Gustav Steinbrecht (1808-1885) in his book “The Gymnasium of the horse” devoted several chapters to “bending / bending” What he describes in his book, from a modern point of view, is largely scientifically outdated information, but let’s see what the author was trying to tell us.

In the original German version of Steinbrecht’s book you will find the following chapters: 1. Flexion of the neck; 2. Flexion of the back of the head; 3. Flexion of the chest; 4. Flexion of the back; 5 Flexion of the hind legs.

In chapter 3 he discusses the ribcage region, the rib region, and chapter 4 deals with the lumbar region, the region behind the saddle. Currently, in the English version of the book, chapters 3 and 4 are combined into a chapter called “Bending the spine”, but it is interesting to study the original chapters in the spirit of the times:

Steinbrecht speaks of “flexing the ribs” and “flexing the chest”. What he means is the convergence of the ribs on the concave side of the horse. The author writes (пtranslated from the original German edition): “A correct and well-placed ribcage, or lateral flexion of the vertebrae of the back, is the chief characteristic of a good riding horse…… it is the soul of the art of riding…

… as part of the spine, the vertebrae of the back must flex laterally according to the same rules as the cervical vertebrae, but they are easier to work with because they are fixed by the ribcage and therefore have less tendency to kink or kink incorrectly.”

Over the years, science has brought new knowledge to the field of spinal movement: the horse evenly “bent” from head to tail, but modern research has proven that this is anatomically impossible due to differences in flexibility in different parts of the spine. We now know that rotation is required to create the “illusion” of side bend.

Steinbrecht often describes the illusion of bending that he “sees”, but what he “feels” is a combination of bending, rotation, and/or flexion in certain areas of the spine: “The rider learns about the correct, well-placed flexion of the chest of the horse by the feeling of comfort and security in the saddle, accompanied by a slight tendency to shift inward …” He further writes: “… the tendency of the rider to move inward, keeping both bodies in harmony, and at the same time complying with the laws of action of centrifugal forces when moving along curved lines … “.

Today, “side bend” is still the most useful image and metaphor among riders and trainers because when a horse “feels” and “looks” evenly bent from head to tail, it arcs and turns while maintaining balance, without falling inward through the inner shoulder and outward through the outer. And this is the most important thing.

But, again, we see how the body evenly “bends” in the spine from the back of the head to the tail, but anatomically it is clear that this is impossible, and let’s see why:

Lateral curvature of the spine

The spine can bend left and right, but is not equally flexible along its entire length due to the characteristics of the vertebrae:

Region 1: 7 cervical vertebrae. This is the most flexible part of the spine, so the horse can easily bend his neck. The neck can just as easily “overbend” without being aligned with the body.

Region 2: 18 thoracic vertebrae. This is a relatively stiffer and more immovable area, the reason for which is its connection with the ribs. Each rib is about 3-4 cm wide, and the space between the ribs is also about 3-4 cm. This is necessary for the horse to breathe. The first 8 pairs of ribs are connected at the top to the first 8 thoracic vertebrae, and at the bottom they are connected to the sternum / sternum. The mobility of the other 10 vertebrae and 10 “false” ribs is not much greater. Thus, the flexibility of the thoracic spine is limited due to the connection with the ribs. And therefore, bending the ribs according to Steinbrecht is anatomically impossible.

Region 3: 6 lumbar vertebrae. This area is more flexible because it doesn’t connect to edges. But there is a limitation due to the large lateral swings of the limbs, the bones could collide with each other if there was too much lateral flexion in this area.

Region 4: 5 connected sacral vertebrae. This area is not flexible and cannot bend because the vertebrae are united in the sacrum.

Region 5: 15-20 tail vertebrae. The tail usually moves to the left when the horse is turning left and to the right when it is turning to the right.

Flexibility of each region (neck, chest, region behind the saddle, pelvis, tail) depends on the shape of the vertebra (body, spinous process) and its design (connection to ribs or other vertebrae). Thus, the flexibility of the spine is different in each part of it.

The neck is the most flexible part (1), followed by the lumbar region (3). Bending in the region of the ribs (2) is possible with difficulty, and the vertebrae of the sacrum (4) are interconnected and cannot bend at all.

Therefore, when we ride in circles or do lateral movements, certain vertebrae and parts of the spine must also rotate and contract, and this three-dimensional spinal movement creates the “illusion” of a lateral bend in the body.

LFS

Let’s see what happens in the horse’s skeleton when we work in a circle on straightness within LFS.

Part 1. Cervical vertebrae.

The lateral bend is relatively even throughout the length of the neck, and the horse can easily ‘over’ the neck, so we need to keep an eye on that.

Elongation/compression is greatest at the joint that connects the head to the first cervical vertebra. This joint allows the horse to shake its head as if it were saying yes. This ability allows the horse to go over the vertical while working. When working on straightness, we ensure that the neck of the horse stretches “forward”, and the nose – “down” and slightly ahead of the vertical. We avoid lengthening the neck because the higher the head and neck are raised, the more the back begins to sag and the shorter the steps of the horse’s hind legs become.

The first two cervical vertebrae have much more ability to rotate than the other five, which is why the horse can tilt and rotate his head during work (the ears are not at the same level, one is lower than the other). The horse may begin to turn his head to the side if the rider uses too much pressure on the inside rein. But this lean can also be the result of the inside hind leg not stepping well under the horse’s body, because what happens at one end of the spine is often linked to and affects what happens at the other end.

Part 2. Chest and rib area

When it comes to lateral flexion, the ribcage area of ​​the spine is very limited in its ability to flex due to its connection to the ribs. The first 8 ribs are even stiffer due to their connection to the sternum. Therefore, to create the “illusion” of a lateral bend in the body, rotation is necessary.

Correct rotation of the thoracic vertebrae allows the rider to sit inside while working on straightness (probably because the inside stirrup drops a little lower), but the horse must be supple to allow for proper rotation.

Tension in the muscles and flexion of the neck can interfere with proper rotation in the thoracic region. When the rider overextends the horse’s neck, combined with a shift in the center of gravity to the outside shoulder (falling on the outside shoulder), he and the saddle often slide outwards (the outside leg and stirrup drop much lower than the inside). Also, proper rotation can disrupt the rider’s displacement of the impact of the external seat bone during lateral movement.

Elongation/contraction occurs in the chest area. It’s about sagging and rounding the back. When a horse carries a rider and its back sags, there is a risk of “kissing vertebrae”. Therefore, when working on straightness on top, we always encourage the “forward down” trend.

Part 3. Lumbar region (the area behind the saddle)

Through a combination of flexion and rotation of the lumbar vertebrae, the horse can perform the hip-in exercise (pictured above).

The junction of the last lumbar vertebra and the sacrum (lumbosacral joint) – after the neck – is the most flexible area when it comes to lengthening/compression. You can easily see this during a sliding stop, when the horse lowers his pelvis as far as possible.

Part 4. Sacrum (the area where the hind legs connect to the spine)

The sacrum consists of five interconnected vertebrae, so it cannot bend, only rotate. The hind legs are connected to the pelvis, which is connected to the sacrum through the sacroiliac joints. As the horse circles to the right, the right hind leg will step further under the center of gravity.

It is very interesting to watch the horse from above while walking in a straight line (see video below). The pelvis can be seen tilting from side to side depending on which foot is on the ground. This up and down movement is transmitted through the sacrum to the lumbar vertebrae and then to the chest area, so the horse’s stomach swings from left to right and back.

(Video available at https://www.facebook.com/camila.morandini/videos/10207610330128747/)

Spinal motion studies

A significant amount of research has been done to determine the amount of motion in three directions in different regions of the spine. In addition, the equestrian literature contains many different, often conflicting, opinions about the movement of the spine.

Research results are often presented in inches/centimeters, percentages and degrees, and are sometimes offered as “absolute truth”.

I will give some examples.

The results of some studies show that the maximum possible curvature of the entire spine is 15 cm, the results of others – 18 cm.

Some results indicate that the greatest amount of rotation is observed in the chest area at the level of the 11th and 12th thoracic vertebrae. Other results indicate a decrease in rotation from 9th to 14th. Another source states that the greatest rotation is possible at the 18th thoracic vertebra, because it is associated with the lumbar region, and the possibility of rotation of the lumbar vertebrae is greater than that of the thoracic vertebrae, because the downward tilt from the pelvis and sacrum caused by the engagement of the inner hind leg horse, is transmitted forward along the spine through the sacrum, to the lumbar vertebrae and to the thoracic vertebrae.

Some books state that the thoracic vertebrae should rotate outward, others state that they should rotate inward.

Some reports describe specific horses with an “S-curve” where the head and neck are bent in one direction and the ribcage in the other, so the thoracic vertebrae rotate in the opposite direction to the curve of the neck. A number of reports indicate that every horse inherently has an “S-shaped bend”: “left-bent” horses are bent at the neck to the left, and their thoracic vertebrae rotate to the right (and vice versa, in the case of right-bent horses). Thus, the literature states that the thoracic vertebrae have a preferred direction of rotation that will be maintained no matter which direction the horse is moving. The neck bends to the left or right, and the vertebrae of the chest area continue to rotate in the same direction.

The reason why there are different results, opinions, and “truths” is because context is important when it comes to research and experience.

Importance of context

It is very important to look at each study, analysis, experience, book and article in its context.

Some research is done on dead horses when the most extreme modes of movement can be measured. Studies conducted on live, naturally moving horses show different results.

Sometimes the analysis is carried out on the example of an untrained horse (horse with natural asymmetry, enslaved and not elastic). Such studies can be contrasted with those conducted with trained (straightened and flexible) horses.

Sometimes some studies are done on large warmblood horses with long backs, while others are done on short horses with short backs.

Research can be done on a single horse or on a group of horses. Some studies involve race horses, others dressage horses. Some studies are done at the walk, others at the trot or canter.

Sometimes the number of movements between two vertebrae is mentioned, and sometimes the movement of one vertebra is observed in 3D.

Some books describe processes based on lunging horses with side reins, others are based on loose horses.

Some authors describe a bend/rotation theory based on riding with constant equal contact on both reins, others base their theory on riding with a flexible/soft inside rein and contact on the outside rein.

Many similar examples can be cited that cause contradictions. It is pTherefore, when dealing with written materials and scientific research, it is always important to understand their context and the basis on which the results are based.

Whether the rider rides with constant or strong contact on both reins or whether the inside rein is relaxed to allow the horse to seek out the outside has a huge effect on the movement of the spine.

It also makes a huge difference whether the horse is being worked “on the bit”, “behind the vertical”, “resisting the hand” or “seeking the hand” – all four styles will affect the movement of the spine in different ways.

The asymmetry of the rider in the position of his own pelvis and spine also affects. And the way the rider sits during lateral movements – inside or outside.

To be clear, this article is not meant to be a “truth-seeking” or dive into detailed scientific discussion. I wrote it only to show the “big picture” and to understand that there are different “truths” and “opinions” and they can be true in their own context. But we must be careful with generalizations!

Remember the story about scientists:

“Five scientists on a train travel through Scotland. They look out the window and see sheep in the pasture. The first says: “All sheep are white.” “No, all the sheep in Scotland are white,” protests another. “No, all the sheep in this pasture are white,” says a third. “No, this sheep is white, ”a fourth voice gives. “We can say with certainty that the side of the sheep that faces us is white,” sums up the fifth.

Just observe and define your own individual base position:

• What equestrian discipline do you practice?
• What is the breed, age, condition, stiffness, asymmetry, degree of training of your horse?
• What style of riding do you practice, how do you use the reins (contact / free rein / on the reins / behind the vertical / resisting the hand / yielding / finding the hand)?
• Are you left handed or right handed?
• What about preference in using your legs, which one is dominant?
• How do you use your seat and center of gravity?

What is most important?

When you know your basic position, the most important thing is to reduce imbalance and stiffness in both yourself and the horse. It is important that you and your horse develop symmetry in the body and limbs so that you strive for the correct balance in riding, which will help you avoid unnecessary wear on the horse’s front legs and back.

Remember: by nature, the horse prefers one of the sides, fore and hind legs, it is easier to work to the left than to the right or vice versa. This preference and dominance not only causes stiffness when we start to ride, but also causes a diagonal shift in the center of gravity (red dot), which leads to a fall over the outer or inner shoulder (where she is unwilling and unable to turn).

When this happens day in and day out, in extreme cases your horse may begin to limp on that “supporting” limb because he is carrying the most amount of weight each time. Also, this shift negatively affects the health of the horse’s back. Diagonal imbalance is a destructive phenomenon and must be avoided if we want to ride a horse without harming its health.

It is important to teach the horse to turn correctly in both directions, to train him to maintain the center of gravity in the correct position and to step under it with his back foot. Only then can we shift the center of gravity to the rear in order to develop the carrying potential of the hind legs.

LFS is key

To teach a horse to turn properly, we need an LFS where L, F and S are closely related.

By asking the horse to stretch and bend forward, to go forward on the rein, we relax the longissimus dorsi muscle, encouraging the horse to stretch his head forward.

The lateral bend we provide on the reins or on the lunge affects the lumbar region and pelvis, prompting the horse to step with the inside hind leg under the center of gravity. At the same time, when we encourage the horse to step under the body with the hind legs, it affects the pelvis, loins and chest, improving the lateral bending of the whole body from the hindquarters, which causes the horse to yield to the inside rein and seek out the outside one. Thus, we can and should work with the lateral bend of the body in both directions.

When the horse pulls forward and down, it activates the hind legs: they swing and move further towards the center of gravity, taking ever wider steps forward.

Thus, the first three keys are closely related to each other and cannot exist one without the other. It is necessary to train the horse in harmony.

That’s why we use the term “LFS” to focus on these three keys as a whole while working on straightness.

When working on straightness, we practice LFS first in the hands and on the lunge without burdening the horse with the extra weight of the rider and, as the horse becomes more symmetrical in body and limbs, we begin to work under the rider.

LFS allows the horse to follow the path of the arc in both directions while maintaining proper flexion. The correct amount of flexion/rotation in each area of ​​the spine will be set automatically as you focus on maintaining LFS:

And once the LFS is reached, the horse’s hind legs will be able to take the weight following the logical system of progressive exercises.

Maraica de Jong (source); translation by Valeria Smirnova.