I am a black belt and I always enjoyed the physics behind karate as they are often more complicated than most people first think. When two people line up to fight, they both bring a certain amount of kinetic energy to the fight. This is determined by their weight, height, muscle strength and also their physical health. The main principle behind karate is to use your body to channel this energy and make maximum use of it. It also focuses on how you can take away from your opponents with smart blocking a defense maneuvers. We can often base the power of these punches on F=ma^2. Since our mass is going to be constant it is important to find ways to increase our acceleration of the punch to generate more force. When you combine this with the ability to channel and make most of your kinetic energy, you give yourself a huge advantage in any fighting situation.