now the quads should tell you exactly where they are located by the burning sensation you feel in front of your thigh. The next one to make itself known will be the biceps. You can find it on the side of your thigh. Since your knees are still bent, they feel hard. Experiment a little and feel the biceps change as you straighten your hip, bend less and more in your knees and straighten them. Now just lift one leg up and bend your knee and see that again the biceps do a part of the work. Please have a seat again. This little exercise showed you that as long as you were bending and straightening your knees, your muscles did not ache, at least not right away. As soon as you stayed in the bent position, almost instantly your muscles began to burn. The horse feels much the same way as we ask it to bend more and more in the hindquarters for collection.

      This was a short description of the support system on the other pillar of the bridge. Now let us look at the bridge itself. It is elastic, and as we apply tension to the support cable either from the front or the back, the bridge is lifted. As we reduce the tension it sinks down. That is the swinging of the back we all want from our horses. The major component in the center part of the horse is the long back muscle, G. It is directly attached to the neck at the seventh vertebra and originates at the first sacral vertebra attaching on all vertebrae of the back. It is also connected to the stretching muscles of the hindquarter and has to work in unison with them. This muscle is the center of the horse’s movement and must not be tight. It connects front and rear of the horse and must not be given the task of holding the back up. Since it is an action muscle, it would fatigue quickly if held in a static position.

      We now have a clear picture of the horse’s skeleton in our mind, and we know how the muscular support system is connected to the bones and joints. Let us observe the horse in motion and see why the horse is such an ideal animal to ride. Our horse is at a trot, all warmed up and on the bit. The hindquarters are the motor of the horse. To explain the actions of the muscles, I divide the movement of the hind leg into three phases: the swinging phase, the carrying phase, and the pushing phase. In the swinging phase the abdominal muscles, E, the long loin muscle, F, and a part of the quadriceps, B, bend the hip and pull the leg forward. During this time, the muscles A, B, C, D and G must relax and allow themselves to be stretched. As the biceps, C, and the long seat muscle, D, come to the end of their length, they passively bring the hock and stifle into an almost straight position. The second phase starts when the hoof hits the ground. At that moment the muscles are still relaxed and allow the weight of the horse to stretch them a little farther, bending the joints more, but not allowing them to collapse. This is where the muscles must work the hardest. At precisely this moment the trainer tries to improve the gait. She half-halts to give the weight of the horse more time to bend the joints farther and this way get a stronger recoil. (This is tiring for the horse, and after a while of riding these muscles begin to fatigue. The horse then starts to resist by stiffening its legs.) At the moment of maximum stretch, the croup is bent forward-downward and pulls on the supraspinous ligament, lifting the back. In the next phase all the stretch