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It is never wise to tell David Goggins he can't do something.
In the late 1990s, Goggins used to weigh 297lbs. Now, reports the Today Show, he's a US Navy SEAL turned ultra-marathon runner, with aspirations to break the world record for the most pull-ups ever in a day.
He attempted to break the current pull-up record -- 4,020 in one day -- in late September, but had to stop after injuring his forearm 2,588 pull-ups into the effort.
The point of the stunt? The same reason he runs ultra-marathons: "I run these races to raise money for fallen soldiers' kids to go to college", he explains on YouTube.
According to KPBS, his work raises funds for the Special Operations Warrior Foundation.
And while Goggins fell short on this attempt, we're certain that isn't for lack of effort: In 2008 he finished a 150-mile ultra-marathon. According the video "Human Machine," Goggins came down with Pneumonia 90 miles into the race -- and still finished.