You are forced to punch a tree 5,000 times in the day and into the night,then you have to punch the jagged edge of a can until your hands have bloody cuts and puss on them,then we make you punch a pile of salt feeling further pain,while you hands go numb and begin healing.
The results are fists with dead nerves and the weight of a brick from dead cells making you capable of punching someone to death without feeling pain.