Ya our instructor broke a board with his pinky finger, pretty impressive.Hint:. The martial arts people that look impressive breaking boards strike them along the grain instead of across the grain. They just concentrate enough force in the right spot. It really takes little force. Just like it takes little force to break a human bone joint if you apply that force in a direction the joint isn't strong.
Don't need to be big and tough at all. Just apply a little force concentrated in the right spot and direction. Kind of like how people can lift big, heavy stuff if they do it the right way but then screw up their back by just stepping wrong without the added weight.