im sorry about the topic i didnt know how to put it any other way in short sentence. sometimes i dont even understand myself lol. well what im trying to say is that ive seen alote of fighters with so called iron chins eventually go down. like julio cesar chavez and roberto duran. im guessing they lost there abillity to take a good punch cause they started using drugs and that made there brain weaker. or am i wrong and everybody is vonerable to get knocked out no matter how good of a chin you have?