The sine like movements isn't hard to learn, and when you've trained it a few years, you'll start wondering how other styles manage to hit hard when they don't have this movement (this is NOT ment as dirttrowing against other styles/arts)!!??!?!? The fact is that with this movement you can concentrate your mind on one thing: release all of your power when you are trough wth the movement and the fot "lands", example: From a walkingstance with a low block (gunnun so palmok najunde/laine magki) you are about to go forward in another walking stance, but punching. So you bend your knees and reaches the lowest point when your feet are parallell. You strech them out on your way forward, and when you are getting close to the length etc that your stance should have, you "land" your foot at the same time as you're punching. It's very difficult to explain... searh for videos of patterns to see it by yourself, or seek out a Chang Hun TKD school