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Talking about the afternoon nap, which is a strong tradition in the French racehorse industry, an old vet told me, “In the afternoon they try to repair the damages created in the morning on the racetrack”.
It was in the 1970s and the concept of microdamage was already hinted at. The old man was semi-retired from a successful career, sharing his time between the golf course and a few selected customers. He had the serenity of a man who has done a lot and does not have to feel challenged by new ideas. He was the type of vet who cared for the horses, refusing to use drugs for one more performance when he felt that the horse should not be asked for this one more race or jumping course or dressage test.
I saw him responding angrily to the request of a trainer, “I am there to take care of the horse, not of your ego.” I liked him for that but he told me back in the car: “As soon as I start the engine, another vet will come and give him what he wants.”
I was interested in the practical application of advanced research studies for performance. My thoughts were on better preparing the horses for the athletic demands of competition. Often, I asked him questions and he became interested by the practical application of what he regarded as “non-applicable” scientific findings. He is the one who introduced the thought that the capacity of correcting kinematic abnormalities for better performance could also be used for therapy.
It was the afternoon of a sunny day. He often spent a few hours watching my horses working. He stood up as if he had just made a decision, telling me:
“I understand that you do it for performance because you are young and you like to win. I greatly respect the fact that you prepare efficiently your horses for the athletic demands of competition. You will grow older and sooner or later, keeping the horses sound will become your first priority.
“Once you will have won so many blue ribbons that you will no longer be impressed by another one, you might direct your passion for the horses toward a much more useful and rewarding priority. You will win their soundness. And I am going to give you a taste of that right now. I will be back in about one hour, with a lame horse. I think that what you are doing is going to help him. I have taken care of his lesion, over and over, but the same problem comes back.
“I am not trained to figure out where the root cause is and I can see that consciously or not, it is what you are doing. If a horse resists, you try to find why, instead of deciding that the horse misbehaves.”
As I objected that this was not my field of expertise, he reassured me, saying: “I will help you. I cannot help this horse with what I am trained to think and do. I think that your constant search for finding the root cause is what this horse needs.”
We found the root cause and we corrected it and the horse became sound and above all, remained sound.
The old man said, “As veterinarians, we are trained to think that back problems are the outcome of leg problems. I watched you focusing on proper functioning of your horses’ back and I saw changes in the kinematics of your horses’ limbs. You approached the problem totally the opposite way. In your mind, the problem starts in the back and I effectively see correction of abnormalities through better coordination of the thoracolumbar spine and associated muscles. That is what pushed me to think that if you can improve limb kinematic abnormalities from good to better, you can apply the same technique to improve it from abnormal, lameness, to normal, soundness. This is why I decided to try with this horse. I think that if you keep working in this direction, you are going to open the door to a new generation of therapies.”
He then added. “But at first, the doors will be tightly closed.”
Indeed. the doors were tightly closed and while many gradually opened, some instead, build a higher wall. The patterns of the wall builders are always the same. They start with a scientific finding and they made up deductions and conclusions that go far beyond the findings that the original study effectively demonstrated. The process turns scientific findings into fantasies but in their mind, their deductions and conclusions became their scientific references. They refer to the process as “having an open mind”.
From microscopic, to neurologic, to muscular, serious scientific researches demonstrate that sound motion is the outcome of proper locomotion.
Remember the introduction of this study.
At every level, mechanical stresses (movement) are critical for the control of tissue form and function. Muscles and bones actively remodel in response to changes in exercise and response to mechanical stresses. This is actually a fundamental feature in all living tissue. At neurological level, the fundamental principle of locomotion is a very large number of what can be compared to minuscule engines having each of the elements they need for the movement or part of movement that they create. They are called “Central Pattern Generators.”
The central pattern generators are stimulated by the central nervous system in a specific number and order to create a complex movement. The central pattern generators involved in locomotion are turned off when the horse is standing still.
“Movements are generated by dedicated networks of nerve cells that contain the information that is necessary to activate motor neurons in the appropriated sequence and intensity to generate motor patterns. Such networks are referred to as Central Patterns Generators, (CPGs). The most basic CPGs coordinate protective reflexes, swallowing or coughing. At the next level are those that generate rhythmic movements. Some, such as respiratory CPGs, are active through life, but are modulated with changing metabolic demands. Others such as locomotor CPGs, are inactive at rest but can be turned on by signals from command centers.” (Sten Grillner, The Motor Infrastructure From Ion Channels To Neuronal Network.)
The central pattern generators can learn from each other independently from the brain. Hence when they have learned improper movement, they repeat and even protect improper movement. They can relearn correct movement but only through the repetition of correct movement.
At the level of muscles, tendons, fasciae, ligaments, nature has developed a sophisticated cycle or energy saving and reuse. The concept is easy to understand. Focusing on the long tendons of the lower leg, the distal limb of the horse has been shown to function like a pogo stick, storing and returning energy in long, spring-like tendons throughout the gait cycle (Biewener, 1998 Wilson et al., 2001).
It demands less energy for a tendon to elongate and shorten than for a muscle.
“The elastic energy stored in and recovered from tendons during cyclical locomotion can reduce the metabolic cost of locomotion” (Cavagna et al., 1977; Alexander, 1988; Roberts et al., 1997).
When properly set, the phenomenon of storage and reuse of elastic strain energy, is so efficient that it greatly reduces the work of the associated muscles.
“The ability of the muscle-tendon units to recover elastic strain energy is apparently energetically so advantageous that the most economical stride frequency in running may be set by this key component alone.” (Paul C. LaStayo, PT, PhD. John M. Woolf, PT, MS, ATC. Michael D. Lewek, PT. Lynn Snyde-Mackler, PT, ScD. Trugo Relch, BS. Stan L. Lindstedt, PhD. Eccentric Muscle Contractions: Their contribution to injury, prevention, rehabilitation, and sport. Journal of Orthopaedic & sports physical therapy. 557-571. Volume 33, No. 10, October 2003)
There are many different architectures allowing many different nuances in the concept of storage and reuse of elastic strain energy. For instance, just for the long tendons of the lower legs, the muscle that is ensuring proper tension of the deep digital flexor tendon is constructed with longer fibers as the deep digital flexor tendon is less elastic. By contrast, the muscle ensuring proper tension of the superficial digital flexor tendon has shorter fibers as the superficial flexor tendon is more elastic. During the first half of the stride, each muscle optimizes the storage of elastic strain energy in the tendon, ensuring proper tension of the corresponding tendon. Releasing these muscles would alter their capacity to ensure proper tension of the corresponding tendon and consequently the power and amplitude of the stride. The thought that greater amplitude in the limb’s movement can be achieved releasing, or elongating limb muscles is inconsistent with actual knowledge.
The concept of elastic energy stored and reused is not limited to the long tendons of the lower legs. Muscles such as the serratus ventralis of the foreleg or the tensor fasciae latae of the hind legs are surrounded by broad pieces of elastic tissues acting like tendons and named aponeurosis. The elastic strain energy stored in the aponeurosis of the propulsive hind leg during the first half of the stride is the main force bringing the hind limb forward during the swing. The fundamental principle of locomotion is not stretching, lengthening or release. It is instead, muscles ensuring proper tension of the tendons and aponeurosis in order to maximize storage and recovery of elastic strain energy.
The importance of muscles ensuring proper tension of the tendon goes far beyond efficient locomotion. When several tendons are attached to a joint, they are part of the joint’s stability. In fact, the joint alone would not be able to support the intensity of the stresses. When the muscles ensuring proper tension of the tendons are elongated, stretched or released, their ability to ensure proper tension of the tendon is compromised as well as the stability of the joint.
The concept of energy stored and recovered is even broader than the tendons and aponeurosis as the muscles have the capacity to store and recover elastic strain energy even in the absence of tendons.
“Apart from the role of tendons and collagen in energy storage, the muscle itself stores and recovers elastic strain energy, as elastic strain energy can occur in the absence of tendons.” Sound and efficient locomotion demands that within the muscles’ belly, contractile cells and tendinous components are tuned to the stride frequency. There is a frequency or cadence that is proper to each horse and sound locomotion can be achieved only by respecting the horse’s frequency. When trainers and judges advise “more forward,” they think at a superficial level and create damage at deeper levels.
The purpose of this series in mechanoresponsiveness is making riders aware that superficial theories might appears sound and logical as long as they are thought through at superficial level.
They become questionable and even damaging when the horse’s structure is studied at a deeper level. The problem is that the horse’s deeper structures are the foundation of athletic performances and soundness. For instance, the concept of “hardening’ bones and tendons trotting on hard surface has been promoted for centuries. At superficial level, the concept of increasing the bone density appears logical. Studies comparing horses submitted to high intensity training with horses submitted to moderated physical activity show thickening of subchondral bone on the group of horses submitted to intense training.
At superficial level, thickening of the subchondral bone can be interpreted as stronger and therefore beneficial. But the same study observed that high intensity training also led to loss of hyaline cartilage stiffness at sites where lesions are commonly observed.
“Forces applied to a joint are dissipated through the entire osteochondral unit, which is composed of hyaline cartilage superficially, subchondral bone plate and cancellous bone.” (R. C. Mura y, S. Vedi, H. L. Birch, K. H. Lakhamni, A. E. Goodship, Subchondral bone thickness and remodeling are influenced by short term exercise in a sit-specific manner, Journal of Orthopaedic Research,19, 1035-1042).
Instead of exposing the bone structure to more microcracks, increasing bone density can be done through appropriated used of eccentric contractions.
The horse industry is basically a sell business and superficial theories are packaged in convincing marketing strategies. The horse does not function at a superficial level. The elegance of athletic performance as well as horse soundness demands education of deeper scales.
Horse owners and riders are ultimately the horse’s protection and the science of motion provides the necessary knowledge.