This is is a video explaining the importance of upper (thoracic) spinal rotation to gain powered in punches and kicks. As Sensei says at the end, speed and power is not just about hip rotation. Spinal rotation improves speed and power enormously, or "infinitely." I guess the spinal spin is a bit like the tail end of the whip, on the end of the hip rotation. To achieve spinal rotation, practice spinning your arm and shoulders with your elbows tight against the front of your body, without moving your legs. To get a feeling for the required upper spinal spin motion, try golf putt practice, leaning forward, and perhaps holding a (putt practice) club. If you do move your legs, try kneeling at first to keep your legs still. If you still can't spin your upper body, then use a resistance band, belt or string behind your back to gain a feeling for upper body (only) rotation. If you are doing it right, with sufficient rotation and speed it should make you feel a bit nauseous because you will be rotating your stomach with your upper body. When you get good at it try different upper body angles as used in different punches. I realise now that the guys that punch hard in my dojo do use spinal rotation. I had been concentrating on hip rotation to get shoulder rotation, but I will try this, also as exercise for my bad (lower) back. Yes. This is good exercise! Thank you. I could not do it at all until I practised leaning forward in the golfing position. ↙(_ _)↘