I haven't the slightest clue, to be honest. In the shin, I would say microfractures that eventually deaden the nerves and calcify the bone, but in the quad/thigh area I'm not sure... maybe it gets calloused? lol I don't know.

Bryan, we spar lightly (30-40%) with emphasis on technique most of the time; it's really the only way to learn and try out new things without having to worry about getting knocked out. However, when a member of the fight team is prepping for a fight, the cirriculum changes... we will rotate the other fight team members into the ring to spar hard (round 80-90% depending) with the person training in order to acclimate them to the reality of fighting someone who is trying to hurt you. At the beginning of this year, I was rotated in with our only 100kg+ fighter for a few days per week and came away from those sessions with a broken left foot, a fractured rib, and a litany of other bumps and bruises. He still got his ass handed to him come fight time. Go figure.