In September 2016, ultra-distance running legend Karl Meltzer set the speed record for traversing the iconic Appalachian Trail—a beastly 2,190-mile-long, 14-state trek through the eastern United States. Starting from Mount Katahdin in Maine, he reached the trail’s southern terminus on Georgia's Springer Mountain in an incredible 45 days, 22 hours and 38 minutes. Having trouble with the math? That's ***47 miles a day***, including one uninterrupted 23-hour stretch. Meltzer didn't best the previous record by over 10 hours all by himself. As he says: "You really have to have a team; it's not just the one guy running."