When John Orth, a violin maker from Colorado, set out to break his own world record for the most pull-ups in 24 hours, he had no idea he was competing against a college kid from Virginia. And that kid, Andrew Shapiro, didnt know Orth had his eyes set on the same number—10,000 pull-ups. No one had previously thought such a feat was possible, and as the two men grabbed their respective bars and started to pull, they would find a new limit to human endurance.