Why do we do it? Is it just for show?
Board breaking is always an entertaining part of our belt tests (higher ranks only). But the purpose of board breaking is more than just audience appeal. It also serves as a lesson to the student as to their technique, which must include:
AIM: The further the strike from the center, the less likely the board will break. This reflects the aim of our strikes against opponents as well. There are key areas of the body that serve as targets or pressure points. We will not be as effective if we cannot hit those targets.
SNAP: The force that is transferred to the board is a matter of physics. While the size of the person striking the board is a factor, far more important is the speed with which the board is hit. A person who hits twice as fast as a person who is twice their size will deliver twice the force and four times as much as someone the same size.
POSITION: Whether it is a kick or a punch, the foot or the hand must be positioned properly or the amount of force delivered will not be as effective. Worse yet, it can damage your hand or your foot if the position is not correct. This is the primary reason we do not break boards until students are intermediate to advanced level.