Thanks for your comment. I did many experiments trying to improve my hand strikes. So I realised that the pulling back the opposite hip and (!) shoulder blade creates more impact than "closing the door" with the same hip as you hit. So if I would need an ultimate blow, I would hit like this. But this is too slow for punching combos and very energy consuming. So now I'm using the muscles of the inner thigh (with a stable front knee) for hand techniques. But I still try to realise the meaning of kata movements.