Punches and kicks should be used to damage the attacker in a self-defense situation. Preferably a strike should do so much damage that it knocks out the opponent with one punch. At least we want the strike to give us time to run away or follow up with a throw or other technique.
In order to do that, first of all, we need to know where to hit. Secondly, we must be able to hit hard.
Every punch and kick has its own technique. However, the physical laws are fundamentally the same for all kinds of strikes. The recipe is simple: In order to punch or kick hard, we need to get our body weight behind the strike. Many people think that speed is the decisive thing. It is not. Speed plays a role, but it is first and foremost a tactical skill. Fast punches and kicks are often hard to block.
So how do I get the body weight behind the punch? First, we need to use your whole body. The arm alone accounts for only about 6 percent of the total power. Therefore, it is no use simply stretching out the arm. The whole body needs to be set in motion. The force must be generated from the feet, via the hips and shoulder and finally to the arm.
Secondly, it is important to be moving forward towards the target as you hit it with your arm or leg. Beginners tend to move first, stop in a position and then hit. This method is ineffective.
Thirdly, we need to hit the target before the arm or leg is outstretched. If not, the power will be exhausted before hitting the target. So-called "skin touch" is an absolutely necessary skill in pointfighting, but not in self-defense where the point is to hit with as much force as possible. To generate power, you need to have something in the "reserve", so that you can punch through the target and not just to the target.