Once in a while, when Chazot is ready for the effort, I am asking for more collection letting him explore the thought of the piaff. The reins are in the left hand and I walk backward. The whip is held above the horse croup keeping him straight. The whip touches the horse on the left side when the he moves the croup to the left or on the right side when he shifts the croup to the right. THE WHIP NEVER TOUCHES THE HIND LEGS. The techniques that are activating the hind legs with a dressage whip are hampering the horse’s ability to perform. These techniques stimulate a reflex that is contrary to the physical demand of the piaff. During piaff the hind legs produce very little propulsive activity. At the contrary, the rear legs develop a large braking activity. The hind limb on support folds resisting forward displacement of the body over the forelegs. "The hind legs have a considerable braking activity to avoid forward movement of the body over the forelegs.(…) The forelimbs have a larger propulsive activity.” (Eric Barrey, Sophie Biau, Locomotion of dressage horses Conference on Equine Sports Medicine and Science - 2002)
The phenomenon is clearly apparent during the sequence in slow motion. The demand is simply collected trot. At first Chazot does not properly convert through the thoracolumbar spine the thrust generated by the hind legs into vertical forces. He is controlling balance holding the neck rigid and braking with the forelegs. The propulsive activity of the hind legs is then lifting the croup higher than the forelegs. After the turn, Chazot properly converts the thrust generated by the hind legs into horizontal and vertical forces and he is then capable to control balance through the upward propulsive activity of the forelegs. The movement is then going through the back and the shoulders. Forward movement is not how fast the horse’s body is moving forward but rather how well the thrust generated by the hind legs is utilized forward through the horse’s body.