Horse Bio-Mechanics

Some of the common indicators that people use to determine if a horse is moving correctly include:

  • An arched neck with the head on the vertical
  • Lengthening the stride so the horse is over tracking its front hoof prints
  • Light or no rein contact
  • Fast speeds or exaggerated movement
  • The fact that the horse can do a maneuver or job

None of these common indicators however prove or disprove balance. They may be present once balance is achieved, but the presence of any one of these peripheral indicators in no way guarantees that a horse is moving in correct balance.

From Dr. Gavin Scofield:

“Because a body is a closed system, balance or imbalance in one part will always affect the rest of the body. In other words, true balance cannot be faked, or indicated in isolation. Every part of the body must be functioning correctly, appropriate to each form, or the entire body will be out of balance.”

Appropriate use of the body can more reliably be assessed through the observation of weight load distribution. If the horse in motion shows greater weight load through the front legs compared to the hind legs, then the horse is not functioning correctly no matter what the frame, head position, stride length, speed or ability the horse appears to convey.

Weight distribution indicates how forces are affecting the general structure of the horse. While a horse is quite capable of compensating to make one of its extremities appear “correct”, weight distribution actually confirms or denies the correctness of the movement. Compensation patterns for overall imbalance then become obvious.

When a horse learns to balance its weight equally side to side and carry a majority of its body weight on the hind legs then many of the popular indicators will begin to emerge as a result. A perfect frame, lengthened strides, power, speed and efficiency in maneuvers or jobs are the end result of balance, but not always the means to balance.

When trying to assess if a horse is moving correctly, it is helpful to know the horse’s body and some basic functions to further understand why weight bearing is so important.

Head and Neck
The head and neck are used by the horse to recover balance or compensate for inappropriate weight distribution through the legs. This area of the body is extremely mobile and flexible so the horse uses it to compensate for a loss of balance or to regain balance much like humans use their arms. The chosen head and neck position of the horse is a reflection of the current weight distribution through the legs. An unstable head and neck position simply reflects unstable weight bearing through the legs.

How this affects training:
“Setting” the head and neck or overly restricting movement with devices or rein contact can inhibit the horse’s ability to find or maintain balance. A rein contact should offer a horse support or guidance from the rider while still allowing a natural range of motion. When the horse is able to freely alter its head and neck position the rider gains true feedback about the horse’s weight distribution and the activity in the hindquarters.

Front Legs
The front legs are attached to the horse’s skeleton only with soft tissue. A horse does not have a collarbone like a human that attaches the arms to the rest of the skeleton. Instead the sling of muscles and soft tissue that connects the horse’s front legs to its body supports the position of the legs and allows an extensive range of motion.
The general shape, organization of joints or angles of the front legs are straighter compared with the hind legs. This design allows the front legs to act like pillars for stationary weight bearing while a horse is resting or grazing. The design of the front legs also shows us the weight load must fall straight through the front legs or they will be compromised. During movement, the front legs reach out and forward to cover ground, but then stabilize during the weight bearing phase of the leg movement. When the horse’s weight is borne primarily on the forehand in motion, the front legs will bear weight while at a backwards angle. When extending or lengthening a stride, it is critical that the front legs do not reach forward so far that they load while in a forward angle.

How this affects training:
Resting a majority of body weight on the front legs while stationary or grazing is a natural state for a horse. Since domestic horses lead a sedentary life compared to wild horses who move an average of 25 miles per day, domestic horses seldom discover how to shift a majority of weight off their front legs during motion. It is important that the training program includes teaching a horse how to use its hind legs for weight bearing in motion. Without active help, domestic horses will most likely continue to function with an inappropriate amount of weight on their front legs, even while being ridden.

Hind Legs
The angular positioning of the bones and joints in the hind legs compared to the front legs allows the hind legs to act as levers. As the horse’s body weight shifts to the hind legs, the joints flex and the legs bend, allowing the body to stabilize in motion and absorb concussion during the weight bearing phase of the leg movement. The flexing of the hind legs also allows the horse to push off the ground with greater force, increasing power and speed.

How this affects training:
While there are many benefits to working a horse at various speeds, most horses must learn how to bear weight on their hind legs during motion before the speed and power can be released with healthy function instead of adrenaline or patterns of compensation. In other words, a horse may need to slow down and shorten its stride for time to learn how to balance its body weight correctly. Allowing a horse to stabilize increased weight bearing on the hind legs first, at any speed or stride length, then allows the horse gain power and agility through correct function.

The Pelvis
The hind legs of the horse are attached to the rest of the skeleton through the hip joint and pelvis. The position of the pelvis and hind legs determine the hindquarter’s relationship to the body and the degree of engagement or capacity for leverage.
A neutral pelvis allows the hind legs to be straight down underneath it. The hindquarter is neither engaged nor disengaged and may be at rest. During engagement of the hindquarter the pelvis rotates up at the front end and down at the back end. This rotation of the pelvis allows the hind legs to reach farther forward, closer to the center of the horse’s torso for stability and leverage.
During disengagement the pelvis rotates the opposite direction, down in front and up in back, causing a loss of stability and leverage. During disengagement the position of the hind legs will be farther from the center of the horse’s barrel, lessening their capacity to bear weight, absorb concussion or create thrust.

How this affects training:
It is a trained skill for a ridden horse to learn how to engage the hindquarters correctly and without tension. The result of practicing disengagement as a training technique can create even more challenges for a domestic horse to achieve correct, engaged motion. Increasing speed, stride length or incorrect lateral work before a horse is stabilized in correct engagement can also make engagement more difficult to achieve.

The back acts as a bridge between the hindquarters and forehand of the horse. When the hind legs flex and pelvis rotates during engagement, the back lifts the horse’s front end which allows greater mobility of the lighter front legs. The muscles of the back must be supple enough to stretch into a complete range of motion during engagement and strong enough to support the lift of the spine and suspension of the front end.
The back is actually lifted back to front and bottom to top – meaning that the hindquarters must engage first. Then, as the hind legs step closer to the center of the barrel, the layers of muscles in the abdomen contract.  The contraction of the abdominal muscles more accurately pushes up the back by lifting the ribcage from the bottom. This process also acts to normalize the pressure in the abdominal cavity helping with gut function and reducing tension in the long back muscle, allowing the back muscle to move through a healthy range of  motion.
The long back muscle (longissimus dorsi) is one of the longest muscles in the horse’s body, attaching in front around the withers and in back around the pelvis. If this muscle is restricted, tense or weakened at either end it affects the entire function of the back. Fascia, a strong, fibrous soft tissue that is less pliable than muscle, covers the back of the horse over the long back muscle as well as the gluteal muscles in the hindquarters and continues down into the hind legs creating a continuous chain reaction between the back and the hindquarter.

How this affects training:
If the back is too tight or tense it will not able to lengthen when the pelvis rotates during engagement. This can have the effect of restricting the position of the entire hindquarter and impede engagement. If the abdominal and back muscles are not strong enough to sustain support while lifting the front end, then adding the extra weight of a rider will make engagement of the hindquarters very difficult for the horse. The back of the horse must be both visibly strong and palpably soft for the horse to function correctly with the weight of a rider. This is why groundwork is so important to successful riding.

The spine runs from the back of the skull through the horse’s top line, right into the tail. Similar to the horse’s back, in entirety it also acts like a bridge. The spine properly aligned acts like a giant lever, lifting the front end of the horse as the hind end lowers, providing stability and power to the entire body. As the spine lengthens or extends, it lifts or suspends and become integrated as a complete unit, which can then act as a lever. Each vertebra in a horse’s long spine moves only a little but each movement is critical. If one joint of the spine is corrupted with too much flexion, too much extension or is laterally rotated out of place, then the entire spine is compromised and its ability to act as one lever becomes extremely difficult. When each segment of the spine is able to operate freely, then the joints can align appropriately, extend slightly and the entire spine can then act as one unit. Correct lift of the spine creates an overall impression of roundness in the horse’s posture during motion without unnatural looking curves in any one section of the spine. The suspension of the spine creates more suspension in the horse’s movement and the entire frame will become slightly more compact from nose to tail. This is not a frame or posture that would appear uncomfortable or difficult with exaggerated curves. It would appear instead almost a neutral but powerful posture with natural and comfortable looking curves.

How this affects training:
There are two different ways to describe, lifting the spine and this term can be a source of great confusion. A spine can be lifted by rounding the back and extending the spine upwards. This is what happens when a horse lowers its head below the withers. While this provides an excellent stretch for the top line muscles, the horse’s body weight also shifts primarily onto the front legs. This “lift of the spine” would be similar to a human bending forward to touch his toes. The back rounds and spine extends outward. A spine can also be lifted by lengthening to extend the joints causing the whole spine to suspend slightly. The extended spine then translates backwards when the horse shifts weight to the hind legs and the back will round slightly as a result of the pelvis rotating and the hind legs bending, stepping closer to the center of the barrel. The overall effect of rounding is similar but not the same as described in the first example – the degree of joint movement differs dramatically. This second example of “lifting the spine” would be similar to a human stretching his body upwards and then shifting his weight onto his heels. The back still rounds but not as much as when he shifted his weight forward to touch his toes.

Because people focus on rounding without understanding the full meaning, some sections of the spine, such as the cervical in the neck, are commonly over stressed. Other sections such as the thoracic (dorsal) vertebrae in the back have to compensate by shifting the opposite direction. Too much flexion in one area creates too much extension in another area and compromises the ability of the spine to function as a whole. Not being able to use the spine appropriately also inhibits the horse’s ability to shift weight backwards. The spine must align first in order to suspend. The “roundness” then happens appropriately as the spine translates backwards as more weight shifts to the hind legs.

The joints of a body are what allows a skeleton to be flexible. If a skeleton was bone to bone without any joints it would be rigid and move awkwardly. Functionally  joints act as shock absorbers, to protect the bones from concussion and stabilize or help balance the body in motion. The motion of the joints also extends the body’s range of motion and provides leverage for maximizing power and strength.
The shoulder joint and hip joint of a horse are similar in that they are both ball and socket structures which allows an extensive range of motion. Ball and socket design accommodates flexion, extension, adduction, abduction and rotation. The detail of the hip joint compared to the shoulder joint are different however; the shoulder is better designed for range of motion while the hip has better capacity for weight bearing. The carpus (front knee) and hocks on the hind legs are also similar designs in that they are comprised of many small bones stacked together. The designs are similar enough to provide both with an excellent capacity for flexion and extension (straight forward and back) but a limited range in any other direction. Again, the detail of the carpus compared to the hock shows us that the carpus is better designed for range of motion and the hock is better designed for stability, weight bearing and thrust. The elbow joint on the front legs is another ball and socket type joint that is wonderfully designed for range of motion but a poor design for weight bearing. The stifle on the horse’s hind leg is actually the horse’s knee, with a patella. Just like the human knee, this joint has an excellent range for flexion and extension but little lateral or rotational ability. The stifle is designed to be used for weight bearing in motion and leverage.

How this affects training:
Just taking a brief look at the design of the major leg joints in a horse it becomes apparent that the horse is better suited for straight forward leg action, flexing and extending the joints, than it is for lateral work. Just like a human, moving laterally is possible but it poses a challenge to the body. If the muscles are not supple enough or strong enough to support and protect the ideal function of each joint while the legs are moving laterally then the forces exerted on the joints can become inappropriate. Inappropriate loading of the joints can seriously compromise their function and integrity.
In simpler terms, premature or incorrectly executed lateral work and repetitive disengaging can compromise joint function. Lateral work and disengaging a horse is often done with the belief that  bending the horse creates engagement and greater flexibility. This work can however have the reverse effect and compromise the horse’s ability to move forward and move correctly.

Muscular System
The muscles throughout the horse’s body will develop to support the habitual function of movement. Whether the horse’s function has been correct or incorrect, the muscles will develop and strengthen to sustain the habitual use of the body. A horse that has been functioning correctly will have smooth, symmetrical muscular development without obvious peaks and valleys from nose to tail. A horse that has been functioning with too much weight on the front legs as a habit will appear more developed and stronger on the front end compared with its hind end. The muscular development of the horse is the result of habitual function. Muscles gain strength through contraction and gain suppleness through relaxing. A balance of strength and suppleness, with a muscle moving though its full range of motion, is what allows the body to move with maximum power and flexibility. A horse that has been habitually functioning out of balance will have a lack of muscle development in some areas and muscular tension in others.

How this affects training:In the beginning stages of restoring a horse’s healthy function from unhealthy function, time and patience are required. When a horse has built muscle around patterns of incorrect function then muscular tension must be released first, restoring a full range of motion to each muscle. Tension free muscles that are able to work in a complete range of motion make it possible to change the posture or function of the body. Once the function has changed, the muscles will strengthen to support the habits of movement. In the process of change, the horse may begin using muscles that were weak or atrophied from previous lack of use. A change in the horse’s way of moving can mean that the horse tires more easily or can do less in the early stages of training. Once the muscles are visibly developed to support correct function, the horse will have more stamina and power than ever before.

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Quote Of The Day

"You cannot train a horse with shouts and expect it to obey a whisper."
~Dagobert D. Runes