Causing sharp pain can be achieved in many ways, but it is not recommended that it be cause by punching. Punching in itself is so specialised. I know that we all clench our fists naturally in times of aggression or anger, but unless you are trained to strike in such a fashion, then punching can cause serious injuries to the to the person actually doing the strike. Knuckles can be broken, the wrist may break. The pain that you receive may even be more than you attempted to inflict in defence ... so ... do not punch!
Let me explain. Punching needs training., like learning to drive a car. Unless you practice you will be very lucky to start first time, and will find it impossible to continue. The martial artists who practice punching are experts at what they do. Karate for instance, exponents have worked hard to achieve that standard, and without practice they would have probably received serious injury.
Any- way, another comment is this - Punching is unnecessary, it is not effective enough to create the proper reaction.
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