Running a marathon in under two hours is impossible.

26.2 miles in 120 minutes requires a 4:34 pace, a speed that would be an all-out sprint for most people and that even exceptional amateur runners couldn't hope to hold for more than 15 or 20 minutes.

The world's most elite distance runners have gotten close—Dennis Kimetto ran 2:02:57 in the 2014 Berlin Marathon, becoming the first man in history to break 2:03. But in a sport where records are measured by the second and athletes fight tooth and nail to shave slivers off their time over the course of a two-plus hour race, the gap between Kimetto's time and a sub-two hour finish is enormous. Would it be possible for the perfect athlete, under perfect conditions, to beat the record by a second—maybe five or ten? Possibly. By three minutes? No way in hell. The two-hour marathon was a myth, a ceiling that athletes could dream of but never really hope to conquer.

Nike disagreed. In 2017, its Breaking2 project was born.

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