Harrisburg, South Dakota
Excellence in Large Animal Medicine and Surgery since 1981!
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Harrisburg, South Dakota Excellence in Large Animal Medicine and Surgery since 1981! |
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Horses As Athletes Horses make great athletics, which is why we ride them. They have the ability to run and jump at a level far surpassing most animals of similar body size. The physiologic adaptations which allow the horse to excel include a large muscle volume, big lung capacity, and large stores of muscle energy, ability to increase the oxygen carrying capacity of the blood, an efficient gait and effective thermoregulation. This article will take a look at some of these adaptive changes by the horse, keeping in mind that as maximum performance increases the risk of breakdown also increases as we have seen recently in the Preakness with Barbaro. It should not be a surprise to us that horses have adapted to run because their flight or fight response is almost always to run. That is the way they respond to a perceived danger. Their first instinct it to bolt away or as some have called it blind flight. Horses where not given horns or protective tough skin; they were given the ability to out run their predators. The changes noted in the horse’s development have all been designed to increase speed and allow him to escape danger. Maximum aerobic capacity refers to the maximum speed that can be maintained for long periods of time. It is something that distance runners refer to and try to increase. Once it is exceeded fatigue sets in very quickly. Horses have 2.6 times more maximum aerobic capacity then cattle. They have 2 times more mitochondria per volume of muscle than cattle; mitochondria provide the energy for muscle contraction. Horses also have an increased cardiac output, increased stroke volume, increased hemoglobin concentrations and a lung size that is 2 times larger. These abilities allowed the wild horse to run fast enough far enough to safely out distance their natural predators, the large cats, which had faster speeds but only for short distances. Greater than 50% of a mature horses’ weight is skeleton muscle this compares to 30- 40 % for most mammals. When a horse is traveling at maximum aerobic capacity 78% of his blood flow is to skeleton muscle. The blood flow brings in oxygen and energy producing glucose to the muscle cells and removes the by products of muscle metabolism which include heat, lactic acid, etc. It is this large percentage of muscle that provides the motor which makes the horse as effective as a runner. Similar to people different muscle types excel in different activities; weight lifter do not make good sprinter and good sprinters rarely make good distance runners. Different breeds have been developed for speed, agility, endurance, or strength. Training for each is different for the desired goal; we will get into this at a different time. A horses gait is very efficient, the tendons and ligaments acts as a spring or energy saving device to store energy for efficient locomotion. As the leg stretches downward in the weight bearing phase of the stride; the tendons and ligaments act like a rubber band storing energy which pushes the leg back upward as the limb leaves the ground. This is a passive process that does not require energy usage. The price that the horse has to pay is breakdown or injury to the tendons and ligaments if over stretched. These tendons and ligaments are very long in a horse which allows longer stride lengths. The horse is essentially devoid of muscle from the knee and hock down. This also helps in speed for a horse by keeping the lower limb light to allow it to be moved easier. It is no wonder that the horse has played such a dominant role in mankind’s history. That remarkable ability to get from one place to another has allowed us to be better hunters, allowed us carry our things as we moved from one place to another, played a major role in many of history’s wars, and currently serves as a major part of many people’s livelihood and recreation activities. It is this great athletic ability and willingness to cooperate with the human that is the reason we enjoy the horse so much and don’t ride cows. |
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