Hip Snap versus Winding
What is winding? Winding is a technique used when in International Taekwondo Federation (ITF) style punching. According to the ITF Theory of Power, to obtain maximum power there should be a forward and then downward momentum associated with a punch (Encyclopedia of Taekwon-Do, Vol. 2, p. 33, 38). Winding involves lifting the punching side heel prior to the punch (forward motion) and then dropping it (backward motion) as the punch is executed (winding is also known as knee spring) (Encyclopedia of Taekwon-Do, Vol. 3, p.16). The motion is sometimes accompanied by upward circling of the punching arm as it is pulled back and thrust forward. When winding, the body moves slightly forward and then drops backward as a technique is fired.
Just as with the sine wave (examined below), winding requires some movement other than those related to the actual attack. Only an inexperienced fighter will cock a punch before throwing it. Although it may add power to the punch, it also adds time and it telegraphs intention to punch. Any motion that is not directly related to the actual attack wastes time and informs opponent of your intentions.
Sometimes, people accept some core belief and then search for justifications for the belief. In this search, they accept anything that sounds good and supports the theory, while rejecting anything that refutes the theory, even if it also sounds good. When evaluating any theory, not just Taekwondo theories, do not except unsupported rationalizations. You do not need a PhD or a 10th degree black belt, just use common sense and rational reasoning.