Good Posture = Efficient Movement
A graphic I made for a student talking about the differences between efficiently striking the head in a basic manner and doing so inefficiently.
There are a few reasons to strike efficiently. Striking is mostly what we are doing in the sword arts, of kenjutsu and iaijutsu therefore we should make sure we have power but without sacrificing proper control, angles and postures that increase efficiency for the strike.
Though this graphic is simple it illustrates the student's inefficient posture which leads to the sword having an improper trajectory.