While the existence of a “central axis” concept is unified in Wing Chun, the interpretation of the centerline concept itself is not. Many variations exist, with some lineages defining anywhere from a single “centerline” to multiple lines of interaction and definition. Traditionally the centerline is considered to be the vertical axis from the top of a human’s head to the groin. The human body’s prime striking targets are considered to be on or near this line, including eyes, nose, throat, solar plexus, stomach, pelvis and groin.
Wing Chun techniques are generally “closed”, with the limbs drawn in to protect the central area and also to maintain balance. In most circumstances, the hands do not move beyond the vertical circle that is described by swinging the arms in front, with the hands crossed at the wrists. To reach outside this area, footwork is used. A large emphasis and time investment in training Chi Sao exercise emphasizes positioning to dominate this centerline. The stance and guard all point at or through the center to concentrate physical and mental intent of the entire body to the one target.
Wing Chun practitioners attack within this central area to transmit force more effectively, since it targets the “core center” (or “mother line”, another center defined in some lineages and referring to the vertical axis of the human body where the center of gravity lies). For example, striking an opponent’s shoulder will twist the body, dispelling some of the force and weakening the strike, as well as compromising the striker’s position. Striking closer to the center transmits more force directly into the body.