It's no big secret, but a lot of people don't even consider training their hands even though it's the hands that are smashed into flesh and bone.

I remember reading that Gene Tunney who admitted that he had fragile hands decided to turn one of his shortcomings into a strength before his bout with Jack Dempsey.

Gene Tunney would squeeze a solid rubber ball hundreds of times throughout the day, sometimes for hours on end, and this he'd keep up on a regular basis. He'd also strengthen his fingers by doing his pushups on them, and working every finger individually py pushing himself off a wall. To strengthen his forearms he took the old-school labor approach by vacationing in lumbercamps in Maine and Canada by shopping down trees and the whole stint.

I recall Jack Dempsey in his book on Championship Fighting attest to Tunney's explosiveness and hard hitting ability that he felt when he fought him. A champion must be a thinking man, doing everything they can do to reach their goals.