US President Barack Obama greets a graduate after she received her diploma at the Booker T. Washington High School graduation ceremony May 16, 2011 at the Cook Convention Center in Memphis, Tennessee. The school is the winner of this year's Race to the Top High School Commencement Challenge. AFP PHOTO/Mandel NGAN (Photo credit should read MANDEL NGAN/AFP/Getty Images)
Pain wasn't just a risk in the 2009 TransEurope-Footrace, which covered an average of 43 miles per day for 64 days straight–it was a given. Researchers tested the pain tolerance of competitors in that year's race by dunking their hands in ice-cold water for three minutes. The runners–all of whom lasted the full three minutes–rated the pain an average of 6 on a scale of 1 to 10. Most of the nonrunners in a control group, by contrast, gave up halfway through the test and rated the pain as 10.
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