Functional Soundness and Spanish Colonial Horses

During our conversations in the mid-seventies, Weldon McKinley told me that they only saw a few signs of the Spanish Colonial horses the first few years they owned the Romero ranch. They set out to catch some of D.D. Romero’s Spanish Colonial horses when they found that hoof prints and manure piles indicated that the herd came to drink at one of the windmills set up for the cattle. . Weldon thought they could get close enough to the horses to rope them if they cornered them in the end of a nearby box canyon after their bellies full of water had slowed them down and they were tired out by running through the deep sandy washes at the bottom of the canyon.

 As planned, the Romero horses bolted for the canyon when they saw Weldon and company riding up on them. But, the riders were barely able to follow the distant dust cloud that showed where the horses practically flew over the land. They got to the end of the box canyon on exhausted mounts just in time to watch the whole herd flow up the near vertical sides of the canyon without ever breaking stride. The Romero horses disappeared over the top of the cliffs into the distance and the riders went home to strategize.

Eventually Weldon recruited a handful of friends and fanciers of Spanish Colonial horses to help chase down the horses during foaling season. He had found spots where he could set up a relay of riders along the path the horses took to water. When one rider’s horse began to tire, a replacement would be ready on a fresh fit horse.

He also wanted the advantage of the herd having a full belly of water, as that usually slows a horse down. So he closed the gates to the water trough for a few days making sure that  the horses would be thirsty enough to come drink even with signs that humans had been around recently. On the chosen day, he had the riders get into position. Then he opened up the gate so the horses could drink.

The riders waited until after the herd drank and were headed back to graze. Then the first rider spooked the herd into a gallop. Weldon had told each rider to sprint after the wild ones. With a horse and rider hidden every half a mile or so, he hoped to keep them at an all-out full speed gallop for as long as possible.

 The Romero horses easily kept ahead of the mounted horses, even when fresh mounts took up the chase. It was only after several miles of pursuit at top speed that the youngest foals began to tire. Just as the herd reached the box canyon, some of those foals finally slowed down enough that a rider on yet another fresh horse could get close enough to toss a rope over their heads. The foals captured that day became the nucleus of the Romero/McKinley horse herds.

The rest of the herd headed up and over the canyon walls and disappeared into the distance again. When I started looking into equine biomechanics, I began to understand how the Romero horses could move so easily through such harsh country for such long distances with showing any sign of exhaustion or injury. I also found support for my speculations on why so many of our free-roaming horses still show such strong Spanish Colonial traits, especially the 90o angle at the hip and shoulder.

Bear with me, as I have to delve into some of the nitty gritty details of functional soundness in horses to explain what I found. Renowned equine pathologist James R. Rooney DVM presented his thoughts on the subject succinctly in his book, The Lame Horse, but I will do my best to make them accessible here. Rooney writes that joint stability is essential to preventing lameness. So I started looking at my Spanish Colonial horse’s biomechanics in those terms

The center of the horse’s mass is called the zero-point or the saddle point. Ideally, that is where we should sit on the horse’s back, so our weight does not disrupt their movement. The horse’s front and hind legs move toward and away from their saddle point, but should never cross it.

If you study photos of horses exerting themselves, you can see that the maximum extension of their hind leg occurs when the femur or thighbone is perpendicular to the ground. Forcing the femur further back as might happen in a catastrophic fall over extends the hip joints. Over-extension of joints causes injuries. The more leeway a horse has between the resting position of a joint and its maximum extension, the less likely they are to over-extend and injure themselves.

Functional soundness means that the horse is built so that each of their limbs and all of their joints stay within the their stable limits even under duress and extreme efforts. When the horse travels smoothly, their limbs and joints are moving within those stable limits. If a horse’s back foot clips the heel of their front hoof, they have exceeded their stable limit. Each joint also has its stable limits. If the joint is over-extended, usually as the hoof pushes off or over-flexed, usually as the hoof lands, the horse is vulnerable to injury.

  • Functional soundness means that a horse’s joints flex enough to absorb the shock of landing, and then extend enough to push off without exceeding their stable limits.
  • Functional soundness means that the joints of a horse’s legs easily transition into and easily sustain their close packed weight bearing position as they receive the brunt of the horse’s full weight as they land and absorb the force of acceleration as they push off the ground.
  • Functional soundness means a horse’s can accomplish all this with minimal muscular effort, as tired muscles are unable to stabilize the joints.

What you do not see when looking at still photos is how much kinetic energy is stored in the horse’s myofascial field, in their tendons and connective tissue. The larger an animal is, the more energy it takes to move. Muscle tissue is energy-intensive to maintain at rest and a metabolically extravagant means of movement, especially for grazing animals.

Storing and releasing energy in connective tissue is metabolically efficient. Connective tissue is made up of springy spiral proteins that store energy by compressing as the horse’s weight lands. How much compression can be accommodated at each stride depends on how much connective tissue can shorten within the stable limits of movement. There are a couple of major and all too often overlooked factors that dictate how functionally sound a horse is:’

  • One is the actual slope of the pelvis and shoulder blade relative to the horse’s spine and the surface of the ground.
  • One is or the angle of the joint itself or just how the pelvis and thigh (femur) or the shoulder blade and the upper arm (humerus) meet each other

Because horses do not have a collarbone I am going to stick with describing the range of movement in the hip joint. Their ribcage is slung in a sling of muscle and connective tissue between their shoulder blades. There are too many variable too consider in their front end, but their pelvis has a fixed connection to the horse’s spine at the sacro-iliac joint. And normally the angles of the shoulder and hip joints mirror each other so the horse can easily maintain smooth rhythmic strides.

I realize a clock face is terribly out of date in these digital times, but the image is still useful to help imagine how quickly horses can reach the limits of the stable cycle of their limbs and joints. Although we say that harness horses or trotters as they cavalry described them,  pull their loads, they actually push them. The collar rests on the horse’s shoulder blades and as they push up and forward, the load moves right along with them.

  • Trotters, or horses bred to work in harness and haul loads usually have a pelvis that slopes at 45o to the ground (1 o’clock on our imaginary clock face) and whose hip joint is an open or obtuse angle of 110o can only swing their thigh from its resting position at 5 o’ clock to full extension at six o’clock. As they must flex their hip just as many degrees as the opposite hind leg is extending to maintain a rhythmic stride, their thigh swings back and forth between 4 o’clock and 6 o’clock.

One of the reasons horses change gaits is to cover more ground at each step without exceeding their stable limits. A trot is faster and bumpier than a walk because it has a fly period. During the fly period, all four feet are off the ground and the horse’s whole body flies forward through the air. Most of our modern riding horses are functionally trotters, bumpy trot and all.

  • The original gallopers, like the Ahkele Tek, usually have a pelvis that slopes at 30o to the ground (2 o’clock on our imaginary clock face). If their hip joint is a right angle, they can swing their thigh from its resting position at 5 o’ clock to full extension at six o’clock. Their normal range of flexion would bring their thigh forward to 4 o’clock. If their hip is an open angle, its range of stable limits shrinks since they can only bring their thigh forward as far as the opposite hind leg is extending  behind if they are to maintain a rhythmic stride.

A three beat gallop usually includes one fly period. A racing gallop adds at least one more fly period and theoretically can include as many as four fly periods. The less time a galloper’s feet are on the ground, the more ground they can cover during each stride. The speed of a galloper depends on how long they stay in the air during each fly period and how many fly periods they can manage in a stride.

A narrow range of stable limits for the whole limb reduces a horse’s ability to store kinetic energy in their connective tissue. The less energy they can store, the more muscular effort they have to invest in each stride. The more muscular effort a horse has to invest in each stride, the sooner they tire.

Once a horse starts pushing its entire weight off the ground, all that weight is forced off the ground and comes crashing back down on the very small surface of the joints and hoof of each leg. Tired muscles cannot stabilize joints, so each joint is more likely to exceed its stable limits. The narrower the range of stable limits of the horse’s limbs, the more prone they are to exceed those limits. A galloper pressed to exert extreme effort over long distance is a horse at risk for injury.

  • The Square War Horse is actually built like the balanced scale prized by both cavalrymen and High School Dressage riders for millennia . They usually have a pelvis that slopes at 45o to the ground(1 o’clock on our imaginary clock face) and whose hip joint is a right angle. Their normal range of extension is from 4 o’clock at rest to full extension at six o’clock. Since they must also flex their hip as many degrees as the opposite hind leg is extending to maintain a rhythmic stride, their thigh can theoretically swing from 2 o’clock to 6 o’clock on our imaginary clock face.

That gives the Square Horse a normal range of stable limits that is at least double that of the trotter and the true galloper. So they store and release more energy at each stride and invest less in metabolically costly muscular effort in moving. Their biomechanics are functionally sound and metabolically efficient.

They hold up under hard use and extreme conditions as well as having tremendous balance, agility and endurance. At first glance, it may appear that small savings at each stride are inconsequential. However, when food is scarce in the wild, conserving energy at each stride can be the difference between life and death.

  • A tired horse is vulnerable to injuries and an injured horse is vulnerable to predators.
  • While the horse who can range far enough to find sufficient grazing and still make to the next waterhole with enough energy to evade predators is the horse that survives the drought.
  • And the horse has the energy to dig through the snow to find food and the strength to deter predators is the horse that survives the winter.
  • And the horse who maintains enough body mass, including fat, to insulate themselves against hypothermia is the horse that survives the storms.

While there are a few bloodlines of Iberian horses here in North America and on the Iberian peninsula that consistently produce truly Square horses, most Iberian horses split the difference between the true Galloper and the ideal Square Horse. Most keep the 90o angle at the hip joint but have a slightly more moderate 35o slope to the pelvis. Whether Square or Rectangular, these horses have tremendous leeway at each stride before they reach the stable limits of their limbs.

They do not need to maintain much metabolically costly muscle mass, but are able to store significant kinetic energy in their myofascial field. Spanish Colonial horses are rarely taller than 14.3 hands and rarely shorter than 13.2. I suspect that the advantages of their biomechanics are maximized at about 14.1 hh high. All in all, Iberian horses in general and our Spanish Colonial horses in particular are functionally sound, metabolically efficient and biomechanically elegant survivors.

  • They can maintain a steady stride with minimum muscular effort over long distances.
  • They can easily vary the length of their stride to manage difficult footing.
  • They have a much wider range of movement to recover from errors in footing without exceeding their stable limits
  • They can scoot forward and get out of danger or compensate for changes in footing without exerting the extravagantly costly muscular effort required to push their entire body mass off the ground

Under saddle, those small advantages at every stride also add up. Frank Hopkins’ famous endurance mount Hidalgo is a renowned example of the huge difference a functionally sound metabolically efficient biomechanically elegant mount can make. Hidalgo was not faster than his competition when they first started out on those long rides.

But, Hidalgo did not rely on metabolically expensive muscular effort or stress his joints beyond their stable limits as he moved. He did not have to take time to recuperate from exhaustion and the injuries that occur when tired muscles cannot stabilize stressed joints. Frank Hopkins did not need to detour in order to acquire extra feed or weigh his horse down carrying it. Grazing while his rider rested at night was sufficient to keep Hidalgo in good condition regardless of how many miles they had ridden. By the end of the ride, Frank and Hidalgo were days, sometimes weeks, ahead of their competitors.

for more on Colonial Spanish and Square horses, click here

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