Rocky "My Boy" Marciano used to eat 25 pounds of tough steaks, he's ask the butcher for the worst cuts, tough as cartilage and nerves and sinew, and chew the shit out of it for 2 weeks beofre each fight, strengthening his jaw muscles. He's suck out all the juices and spit out the grizzle. said it took him 45 minutes a night, for 14 straight nights before the fight, I kid you not.