On another forum I was explaining a shotokan karate side thrust kick (yoko kaekomi). I'm not sure how to explain in scientific terms of physics how the hip rotation adds that extra "shock". Could anyone help me out here? Thanks. Here is what the other guy told me: That kick is used in a lot of arts, mine included. What I'm saying is the rotational force does not contribute to the power of the kick because the final thrusting motion is not at a tangent to the circle that represents the direction of rotational force. You generate a lot of momentum while spinning, but it all stops when you come to that 180 and thrust out perpendicularly to the angle of momentum. See attached diagram. http://www.paulromerproductions.com/images/diagram.jpg