I imagine spending all day rowing and getting whipped wasn't good for anyone's health. How did the men in charge reduce exhaustion and keep them in shape enough to row?
Roman slaves forced to row on ships
There's no such thing. The rowers of ancient warships were, by their very definition, free men. The galley slave is a feature of medieval navies and sword-and-sandals flicks like Ben Hur, not a social reality of the Roman world