The crane boxing to build up energy (or ching): it is better to practice at a moderate speed. PAI Yu-feng said, "The crane's ching is in its feet and its spirit (or shen) at its serenity." To follow this method, you should stabilize ching and shen, relax your arms to do the breathing exercise, thus your shen and will are at ease and your mind and hands cease to bother each other.