Mechanoresponsiveness PT 4
Jean Luc Cornille
Sometime, I watch kids, at the gate of the hunter show ring, waiting on a horse standing still. They talk with others or watch their cellular phone. The horse may stay standing still for five and sometime even ten minutes and then, enters the ring and in a matter of seconds, passes from standing still half way sleeping to executing a jumping course. There is no concept of athleticism, no understanding of the muscular work required by athletic performances, there is no knowledge and as always when knowledge lacks, there is no respect. Whatever the performance is a jumping course, a dressage test or any other athletic activity, it is about the subtle orchestration of a complex biological mechanism. A horse is an athlete and needs to be treated and educated and maintained as an athlete.
The benefits of mechanical stresses (exercise) are involved at all levels of the horse’s structural hierarchy. For instance, skeletal muscles possess two main types of monocarboxylate transporters, MCT 1, which facilitates the extraction of lactate from extracellular fluid, and MCT 4 that facilitates the next efflux of lactate. Lactate is the metabolic fuel of muscles, but excessive accumulation of lactate poisons the muscle. Equine performances can be improved when the glycolytic muscle enhances its ability to remove lactate from within contracting cells. This is significant because intracellular lactate accumulation does have a negative effect on muscle acidosis and fatigue process. By contrast, enhanced rates of lactate removal are associated with a slowing of muscle fatigue and improved performance. “What is important is that these characteristics are enhanced with appropriated training.” (Michael I. Linger, Lactate: metabolic fuel or poison for racehorses? 2011)
Traditionally, anaerobic work is associated to intense physical activity. The concept is very well known from three-day event riders as it is part of the horse’s conditioning. However, the metabolism of horses that are not fit resorts to anaerobic energy earlier than traditionally expected. Some breeds also are prone to anaerobic work earlier than others. A study completes on Andalusian horses estimated that, “The oxygen supply to the active muscles in Andalusian horses seem to be limited at velocities higher than 7meters per second” (A. Munoz, R. Santisteban, M. D. Rubio, C. Riber, E. I. Agüera, F. M. Castejon. Locomotor response to exercise in relation to plasma lactate accumulation and heart rate in Andalusian and Anglo-Arabian horses. 1999). 420 meters per minute is not fast at all. For reference, the time usually allowed during a jumping course is traditionally based on a speed of 450 meters per minute. The study does not discredit the breed. The point is simply emphasizing the fact that efflux and extraction of lactate within muscles is not exclusively a problem of high speed.
Any athletic activity, including dressage and even trial riding, can easily create situations where efflux and extraction of lactate are feeding the muscles. Efflux of lactate is not the problem; the problem is proper extraction. When MCT 1 monocarboxylate transporters fail proper extraction of lactate from contracting cells, soreness occurs as muscles are basically poisoned. Michael Linger emphasizes the need for “appropriated training”. Whatever the specialty, a horse, including a dressage horse, should be under a fitness conditioning program. A dressage horse does not need fast canter work like a three-day event horse, but long and slow trotting as well as slow canter work. Each horse coming at the center for performance, is placed on a conditioning program. It is very well known that once they are used to one type of exercise, muscles no longer develop. Different activities are necessary. The problem with different activities, is that they can stimulates transient muscle soreness. If one hikes regularly up and down hills, one is not at risk of muscular soreness. By contrast, if one hikes up and down hill without progressive training, one will experience great muscle soreness the day after. Walking downhill, one’s leading leg resists attraction of gravity pulling one’s body toward the bottom of the hill. Knee extensor muscles work eccentrically, which is a powerful type of muscle contraction. Eccentric contractions are often referred to as “high power contractions.” During normal locomotion, 50% of the horse’s muscles work eccentrically at one moment or the other of the stride. A trial horse used to flat trial will experience muscle soreness after a walk up and down hill or unstable footing.
Whatever the specialty, equine activities are athletic performances that have to be approached as athletic achievements. Straightening the horse between a pole and the wall is a primitive form of training that exploits the horse talent but let the horse athletically unprepared for the physical demand of the move. This is just an example. Many training techniques only focus on appearances without understanding the underlying biomechanics factors. Real education is about developing and coordinating efficiently the horse for the athletic demand of the move.
Respecting the horse as an athlete should be the fundamental principle of equine athletic training but it is not. Our ancestors were limited by available scientific knowledge and interpreted their feeling in respect of their logic. The picture illustrates an experiment where we recorded vertical forces created by the hind and front limbs and vertebral column mechanism. Knowing through previous experiments that the horse thoracolumbar spine does have a very limited range of motion in the dorso-ventral direction, it is easy to understand that the considerable amount of vertical forces recorded by the sensors and illustrated by the elevation of the dots on the computer screen, are created by the hind and front legs. The two sensors placed under the rider’s seat were the ones recording the greatest amount of vertical forces. The rider is seat exactly where vertical forces created by the hind and front legs meet. Our ancestors believed that the large amplitude of forces moving their back were the movements of the horse’s vertebral column. Based on this belief, they advised following the movements relaxing the rider’s back muscles. This was a misinterpretation creating exactly the opposite effect. The main function of the back muscles is precisely resisting movements that would exceed the thoracolumbar spine possible range of motion.
Harmony between the rider’s back and the horse back cannot be created increasing the range of movement of the rider’s vertebral column but at the contrary reducing the movements induced on the rider’s back by the horse’s hind and front legs, to an amplitude of movement that does not exceed the horse thoracolumbar spine possible range of motion. Leo Jeffcott measured the amplitude of thoracolumbar spine in the dorso-ventral direction and found that the total range of movement was extremely limited, 53,1mm which is about two inches and a quarter.
Harmony cannot be created through relaxation of the rider’s back but at the contrary through variations in muscle tone. It is about reducing forces through controlled movements. Every riding and training techniques use this type of phrases but when they are based on a range of motion of the rider’s vertebral column exceeding the possible range of motion of the horse’s thoracolumbar spine, the phrase is meaningless and the horse has to protect his thoracolumbar structure stiffening the surrounding muscles. Basically, the more relaxed the rider’s vertebral column, the stiffer the horse’s thoracolumbar spine.
Before jumping on your key board commenting that stiffening of the back does not happen if the horse is barefoot or the saddle is properly fitted, remember the fundamental point of this series, living organisms are constructed from tiers of systems within a system within a system. Soundness and excellence of the performance relies on proper coordination of many systems. Proper hoof balance and proper fitting of the saddle are only elements of numerous systems. They are necessary but they are not enough. Respect for the horse is not about reducing the understanding of the horse’s physique to one system or belief. Respect for the horse is at the contrary furthering knowledge and our capacity of adapting our riding and training techniques to new knowledge. Jean Luc Cornille