The Arc of Power- To help visualize how the Concepts of Reference and Yin/Yang Motion interact, imagine that an “Arc of Power” is created whenever the stance is pivoted. Power converts from positive (Yang) to negative (Yin) at the Centerline during a stance pivot, as shown in Diagram HH. If there is no opponent, the Original Centerline is the reference point for determining this Yin to Yang conversion. In the first form, the Original Centerline was established. It is the ultimate point of positive power focus (like the apex of a golf swing) or damaging chambering (as in drawing a bow). As the stance is pivoted clockwise to the right from the Choh Ma position, any movement of the left arm originating from the left and traveling up to and including the Centerline on the Power Arc is said to be Yang in nature. Any proper arm movement that begins at or near the Centerline and moves backward along the Power Arc is considered a Yin, or “receiving” motion. As this fundamental concept is grasped, it will be clear that it is possible to create Yang motions with the right hand and Yin motions with the left in the same situation, depending on the origin and direction of the action.
As previously stated, the Arc of Power can be compared to a golf swing with a “Five-Iron,” with the point of maximum power release on the Centerline. Suppose a golfer places the ball on either side of the Centerline between his feet. In that case, he will hit it before or after his club has reached its maximum power point (the center) or after it has slowed down past the center on its way to a stop. In either case, his stance will be unbalanced as he reaches to either side to hit the ball. The Power Arc functions similarly. Because most Wing Chun techniques are aimed at our center, which is then aimed at the opponent, striking to either side of the center will not only throw the process off balance but will also cause the technique to land either before or after it has gathered its full strength at the Centerline. Any Yang technique that is not focused correctly on the Centerline will lose some of its lengths, as its structure requires it to reach its entire size and power precisely at the Centerline.
The Wing Chun student is taught early in his training to pivot his stance for added power. Stance pivoting, or Choh Ma, demonstrates to the student that a single torqueing motion generates a type of twisting force (Juen Ging) that radiates from every point on the Power Arc. This basically means that when the stance is pivoted, the torque created by the pivot is distributed evenly around the waist, chest, and back. One shoulder advances with the same momentum as the shoulder retracted by the same pivoting motion. Just as Yang motions must refer to the Centerline, Yin motions must refer to an exact point in space. That point is known as the Self-Centerline. As previously explained under the heading The Yin Cutting Angle, Yin motions must refer to a different point in space to have the same effect as their Yang counterparts. This is another example of how Wing Chun’s various combat theories overlap and work together to produce a single result. Complex motions like Gahng/Jom Sau or Tan Da rely on a single stance pivot to power two nearly simultaneous Yin/Yang motions.