Back when I was an undergrad, I'd generally be rowing 2 or 3 hours a day and playing bass for several groups... my hands were something to behold.

The thing that amazes me is that between the rowing, bass, piano, and of course all the typing I do, I never had wrist problems... (I've had minor wrist problems more recently, but I think the rowing and instrument playing and typing canceled each other out or something...)

Oh, right, and when I rowed I'd generally have bruises up and down the outer sides of my legs and thighs...