This movement develops abdominal strength while in a stabilizing mode, which is holding the pelvis and torso absolutely still as the limbs move. The slow extension and stretching action of the legs amplifies the abdominal work and should not affect the stability of the pelvis. The head should be aligned with the spine and stay absolutely still. As one leg is stretched out strong and long, the other knee is bent into the chest, with the shin remaining parallel to the floor and hands firmly on the shin.