I used to practice martial arts and one day in our dojo, my sensei decided that we should have fun by breaking boards. Although breaking a board seems impossible for a person who doesn't do martial arts, it is quite simple if we look at the physics of breaking a board. For example, a person needs to generate a certain velocity to impact the board at a certain position. A person should make the impact/position of where your hands end, up past the board. Otherwise your hand will have a tendency to slow down when it reaches the actual position of the board. Additionally, a person should position their strike on the board where the board it weakest. For example if you punch the center of the board, it is harder to break it because that's where it is the strongest. On the other hand, if you punch a board at the near an end of the board, it will break more easily. It can still be very hard to break some boards because of how the thickness of the board. As the board increases in thickness, you velocity of the strike has to be fast and more precise on the board.