The humor columnist Dave Barry once wrote, “There is a very fine line between ‘hobby’ and ‘mental illness.’” That’s especially true when you consider marathon runners, who train for six months to run 26.2 agonizing, exhilarating miles — toenails be damned. 

And yet, the sport is as popular as ever. The number of U.S. marathon finishers has more than doubled since 1990, according to data from Running USA. At the New York City Marathon on Sunday (Nov. 1), more than 50,000 runners are expected to wind through the five boroughs.

If you’ve ever wondered what forces drive people to such extreme challenges, Yahoo Health asked 20 experienced marathoners (including U.S. champion Deena Kastor!) why they run. Their answers may inspire you to lace up yourself. 

Related: What 12 Marathoners Wish They Knew During Their First Race

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