When i throw for power it helps me if i dip the knee of whatever hand i throw with. For example if i throw a straight right (in an orthadox stance) i dip my rear knee, at the same exact time im pushing with my legs as well. I guess it sounds kind of wierd. Its almost two motions at once but for me its smooth and i get alot of power. If anyone can explain this better help me out. For me the sitting down on your punches would be the dipping of the knees.