fallight.com

What Makes My Walker Different?

by Rose Miller
(reprinted from August 1993)
© Copyright 1999, Voice of the Tennessee Walking Horse, Lewisburg, Tennessee

Tennessee walking horses do possess one rather unique difference from most other horses. Stated simply. . . they have longer hind limbs than most horses that trot. I say "most" because we will see that some trotters have long hind limbs, some to their disadvantage, and some to their advantage, but not with the regularity of the walking horse. First, let's look at the three different types of hind limbs found on horses.

Type 1 is considered to be the best for most uses. When the horse is posed with his hind cannon vertical, a line dropped from his buttock to the ground should graze his hock and the hind cannon bone.

Type 2 has the vertical line dropped behind the vertical cannon bone. This type is found in draft horses.

Type 3 has the vertical line falling within or in front of the cannon bone.

This is found in pacers and gaited horses and is an important point for "all breed" judges to keep in mind, as horses with Type 3 hind limbs will stand either "camped out" or sickle hocked. The horse with sickle hocks is also predisposed to unsoundness, unless the hock is well formed and strongly supported with proper muscles and ligaments. Fortunately, most walkers seem to have inherited strong hocks, but too much of a sickle hock is not desirable.

There are several ways to have a long hind limb, and there are variables on the length of limb. This should be taken into consideration when breeding or buying a horse. With proper "walking conformation" the horse should gait, but do you need a long-striding show horse or a more compact using-horse? Let's see how these differences might work.

Basically the shorter, and therefore straighter the hind limb, the more easily it can deliver the thrust of the hind muscles downward to the ground.

The horse with the longer, crooked or Z shaped limbs, can more easily bring his hocks forward and track up, or overstride.

A walker with less length to his hind legs or less angulation will have less overstride; but he will perhaps be more functional as a horse used in ranch work, jumping, or speed and action events. The walker with the longer, more angulated hind legs can excel in the show ring or on park trails. This difference is seen in trotting breeds as well. The dressage athletes have longer hind limbs so they can extend at the trot, and an overstride at the walk is of value.

The jumpers, however, have shorter hind limbs so they can dig in, thrust, and jump. If you watched the Olympics, you likely noticed that the three day event horses did not perform the dressage patterns as smoothly or as excitingly as did the dressage horses. This is because the dressage stars have conformation conducive to forward stride and fluid movements, not the power necessary for three day eventing.

Now let's look at hind limb construction (as shown in Figure #1) from the hip down to the foot, and see how it works. The horse's pelvic length is measured from the hip joint to the point of the buttock. The larger the pelvis is, the larger can be the propulsive musculature and the more power the horse can produce. An old rule of thumb in conformation judging is that you should be able to divide the horse into thirds. The front one-third is from the point of the shoulder back to the elbow and withers; the back from the withers to the point of the hip another one-third, and from the point of hip to point of buttock is the other one-third. A horse with less than one-third of his body length in the pelvic area won't have the power to push the longer lower hind limbs under the horse as far or as easily as one with greater length and musculature. We also need to look at the pelvic slope. It should be moderately sloped, not tending toward flat, or the horse will "leave his hocks behind" as he travels, again not allowing our walker to stride up under himself.

The next area to look at is the femur, or thighbone. This is an extremely important link in the hind leg assembly. Think of the hind leg as a series of rod like links. First the femur, then the gaskin bone, then the cannon bone and pasterns. If these bones were hanging by themselves and set swinging, they would behave like a chain pendulum in which whatever the uppermost governing link does the rest of the links follow in the same manner.

A long first link, or femur would therefore set the leg in the slower, longer swing. This is part of what can give the walking horse the long slow ground covering stride that we all appreciate. This does not mean that a walking horse with lesser length of the femur won't gait, but it will be a shorter more rapid stride suitable for rougher riding or ranch work. Shorter femurs are desirable in trotting horses that are used in speed events or sprint racing. In a sprinter, long hind limbs prevent the thrust generated by the rump muscles from being delivered to the ground and is a disadvantage. Having a longer femur gives the walking horse longer hamstring muscles which should tie in low to the Achilles tendon. In a profile view of the rear legs, the hamstring muscles should flow down, making that part of the leg appear long. If it appears rounded and the notch in the profile from buttocks to hocks is deeply indented, he ties on high, the femur is short and so is the hamstring muscle. This will limit the forward movement of the hind leg.

The next link on the chain is the gaskin bone and muscle. The pelvic and femur length is often hard to see because of the muscles of the rear quarters, but the gaskin length is easy to see. This is the bone from the stifle to the hock. Most walkers have longer gaskins. However, we need to remember that if the femur isn't also long, the swinging leg pendulum won't produce the long slow stride we desire. If rightly proportioned, the longer gaskin and the long femur are desirable in our walkers. A long gaskin in most trotters is a disadvantage, some exceptions being horses used for dressage requiring extension of rear legs and saddlebreds. Walkers being used as trail horses in rough terrain or working ranch horses won't find a very long gaskin of benefit. These horses will do better having a gaskin and femur more near equal in length. Ideally, in the trotting pleasure horse, the femur is longer than the gaskin in length.

Next is the cannon bone. This bone should be short, so the horse's hocks are close to the ground. High hocks predispose the horse to "travel downhill" especially if they are quite a bit higher than his knees and he will have trouble getting his hocks up under himself, a very important thing to remember with our running walk. A good way to judge the length of cannon bone length is to compare it with the front cannon length. The hock should appear only a little higher than the knee. In the front leg, the upper arm should be longer than the cannon. It is considered good conformation to have low hocks in any riding horse.

In a visit to a standardbred training facility, I noticed that the pacers had gaskins longer or equal in length to long femurs; but in all the ones I saw, the hocks were set high, with relatively long cannon bones. It makes sense when you remember that for racing the pacers need a fast swinging of the hind legs, easier when the leg below the femur is more equally divided in length. This is not the long slow sweeping stride we desire in the walking horse.

In review of the Tennessee walker's long hind limb conformation, we see that the most correct way is to have one third of the horse's body length in pelvic length for power with a moderate slope, a long femur with it's accompanying long thigh and hamstring muscles to provide the long slow swing of his leg pendulum, a moderately long gaskin to give more overreach and short cannon bones enabling him to set his hocks under himself.

The front half of a walking horse has the same problems, faults and good points as our trotting friends. Here again, the use we have planned for our horses makes a difference in what we look for in conformation.

A horse has two bones in his shoulder, as shown in Figure #2. The scapula runs from the point of the withers to point of the shoulders. The humerus or arm bone goes from the point of the shoulders to point of the elbow. How these bones relate to each other determines how a horse moves in front. In talking about how a walker "moves out of the shoulder" we are most familiar with the scapula, or shoulder blade.

However, the humerus is very important and seldom talked about. It is capable of side to side movement, and also swings from back to front, raising or lowering the elbow. It determines the way a horse will fold or unfold the elbow, knee and fetlock joints. It determines the style or way of going of the front end of the horse.
The longer the humerus the more scope the horse will have. Scope is defined as the ability to move the elbow away from the body, either toward the front or to the side. Scope is a very desirable characteristic. To be considered long, the humerus must be at least 50% of the length of the scaupla. Better motion is seen with the length closer to 75%. The shorter the humerus, the more short gaited the horse will be, moving with short, stiff, choppy strides. In our walkers we must have this length to allow the forearm to extend forward. No matter what the length or angle of the shoulder, without a long humerus the horse can't roll out of the shoulders.

The steeper the resting angle of the humerus, the higher the horse can raise his knees. This is of obvious importance to those of us who want to show our horses. The most spectacular natural action is shown by horses with a moderately upright shoulder, around 55 degrees, and a long steep humerus. Hackneys and park horses are good examples. Since we like our walkers to have reach forward as well as natural upward action, the walker's shoulders should be more sloping, between a 45 and 50 degree angle. A very sloping angle of around 45 degrees is found in racing thoroughbreds and dressage stars who need great forward extension, but little knee action. A long upright humerus with a moderately sloping shoulder is what we need if we want natural elevation with as little fuss as possible.

A horse with a more horizontal humerus will have less natural ability for high action or tight folding. He will move with little elevation of his front legs and will have difficulty in raising his forearms to level and may hang his knees.

In order to have a rolling shoulder, the angle between the scapula and the humerus must be at least 90 degrees. Less shortens the forward movement of the whole shoulder. A shoulder slope of 45 degrees needs a humerus angle of 45 degrees to keep a 90 degree angle between. A shoulder angle of 50 degrees needs a 40 degree angle of the humerus.

Many walkers seem to fall into the category of medium angle of the humerus. They may not make high stepping show horses; but their movement will be pleasant. They would probably show well in western, trail pleasure and lite shod classes and be wonderful riding horses. Their shoulder angles are probably between 51 to 55 degrees with a humerus angle of between 39 to 35 degrees. Heavy shoes and other training methods will have less of an elevating effect on these horses.

The humerus with a low angle of 30 degrees or less has several disadvantages. If the angle between humerus and scapula are to be kept at 90 degrees, the shoulder will have to be quite steep, closer to 60 degrees. The shoulder will be long in order to join with the low humerus and this will push the elbow back too far. This results in the horse being "pigeon breasted" with two much of the horses sternum being visible in a side view. This makes the horse heavy in front and he definitely will have trouble going in a balanced way. He will feel like he is traveling downhill, and no training method will be able to get him to pick up his front feet like a show horse. A horse with this conformation will have a humerus angle of around 30 degrees or less. If the shoulder is less than 60 degrees or more sloping, he is in even more trouble because his shoulder isn't open 90 degrees and his range of movement is further constricted.

By looking at the resting angle of the humerus, you can get an excellent idea of how the horse will carry his head. Low humerus, low head, high humerus, high head. By studying the angle of the shoulder or scapula, you can get an idea of how much the horse will extend his front legs. A line drawn from the point of withers through the point of shoulders and on to the ground will show the farthest a horse can extend. This is seen easily in a trotting horse at the extended trot and in a galloping stride. In a walking horse it is harder to see since he uses a more up-and-down front leg movement, but it works the same way - a steeper shoulder, the less forward movement, a more sloped shoulder the more extension.

We see that there are many variations of the shoulder construction, and the resulting movement of the horse. In order to have a very good horse, both the front and the back of the horse need to work in a balanced manner. A horse can stride in front only as far as his hindquarters are capable of pushing him, but a short reach in front will limit a powerful thrust from behind.

By applying these principles of conformation, you can choose the horse you want for the purpose you have and avoid the horse with conformation likely to be unsound and cause him to travel in an unbalanced manner.

http://www.twhbea.com/Voice/Features/walkerDifferent.htm