Educate your eye
Example of Hind and Front Limbs Propulsive Activity
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As Chazot is allows playing for the first time since his night of terror and consequent mild check ligament injury, he gives us a great lesson of hind legs’ propulsion. It is inexact to believe that the compression of the hocks’ joints is producing the propulsive force. Propulsion is created by the system of muscles and ligaments. Eccentric contractions immediately followed by concentric contractions are more efficient in propelling the horse’s body forward than any hock flexion. The whole concept is known as stretch-shorten contraction. The ligaments are part of the propulsive power through their elastic recoil capacity. Chazot starts the move bucking slightly and landing on the front legs. The hind legs alight and propel Chazot in the air. There is no flexion of the hocks at all.
Another interesting feature is the work of the serratus venralis thoracis muscles, (SVT) of the forelegs. In the middle of a bounce for instance, a horse is capable to take off over the second jump before the hind legs touch the ground. The SVT muscles which support the horse’s trunk between the forelegs are capable to propel the body upward. In this picture series, the forelegs are propelling Chazot upward before strong involvement of the hind legs.
Computer studies greatly further the knowledge of how the horse executes gaits and performances. The main finding is that simplicity does not fit reality. In fact simple formulas are most often confusing the issues and introducing false ideas. For instance, exactly the same move, showing the same kinematics data, can be produced by different muscular combinations. “A visually identical hindlimb extension in late stance may be accomplished by only hip extensor muscles, only knee extensor muscles or any combination of these.” (Liduin S. Meershoek and Anton J. van den Bogert. Mechanical Analysis of Locomotion.)
Jean Luc Cornille