We use activity lines to activate from one point on a bone to a point on another bone — so the joints become free to take and respond to the activity. This creates an action that leads and forms the inner flow of energy to later become a movement into space.
The muscles have the purpose to support the action of the activity lines through releasing in order to give space for the skeleton to breath and express the inner voice. Therefore, the muscles are the servant, but not the master of the movement.