The Key to Sitting Trot

It is the goal of the rider to capture and control the power of the horse as it enters the rider's pelvis through the seat bones. This is achieved by actively controlling the 3 movements of the pelvis (left-right movement, rise and fall of each side, and the tilt of the pelvis forward and back) as well as the rotations of the femur bones and the opening and closing of the curve in the lower lumbar and sacrum.
The left-right movement redirects some of the power of the horse down into the femur bones through the knee and lower leg into the foot, forward through the arch of the foot into the stirrups then through the ball of the foot back to the horse. This flow of force has the effect of quieting the movement of the rider’s leg and keeps the heel down by relaxing the ankle and the hip joint. This relaxing is in a way completely passive as it is a result of redirecting the force out of the seat down the leg. The leg can then be used much more effectively with less muscle and more rhythmic power that has been borrowed from the horse.
The amount of force that moves up the spine is redirected by the left-right movement of the pelvis. It is as if it splits and is redirected up the spine in a double spiral. The effect is that the bounce of the trot in the rider's seat is minimized. Instead of the force and power of the horse pushing up into the spine as two strong pulses it now moves in a double spiral up and around the spine. Initially few riders will feel the spiral of energy up the spine; all one can feel is the deeper connection in the sit bones and the lift in the back of the horse. As the force is redirected in this way the effect on the rider's upper body is lessened, therefore the sternum is not lifted and held against the force which in turn means the head does not bounce as much and the arms and hands can be much quieter as a result ….