We see many fighters eating punches early on their careers and after many years suddenly comes a time when just one punch is enough to make them sleep. People often say "his chin is not the same" or "he used to have good chin" or even "now that he lost his chin". On the other hand it is commom to see in street fights people who supposedly never have trained being punched in the head getting KO and even fucking dying So...what makes a chin? It is training? Is it a gift? You must get hit often in the head so you dont get KOut easily? And if you continue to get sistematicaly hit there comes a day when you will lose all your ability to take punches? How does this logic work? Whats the science behind it? Because we have seen this happen to so many fighters... and what type of conditioning is required besides sparring (aka taking punches in the head)? Neck development? Traps? can anyone shed a light on this topic?