How Ali could take Foremans shots but not Frazıers so well?

[Mars_ax]

Physically there is nothing you can train for to take a beating, but if you have the frame of mind and are mentally strong you can achieve any thing.

Yeah alot of it is you have to be stubborn and not give up but you wont take those punches if your unfit.

Ali was still 32 years old when this fight with Foreman took place in 1973, and he looked to be in great shape.
Ali fought a brilliant fight, but I still believe that Foreman gave the fight away, had he paced himself better we would have seen a different result. That was the problem George had no concept of pacing himself and fell right into Ali's trap.