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KAILUA KONA, HAWAII - OCTOBER 10: In this handout photograph provided by Ironman, Daniela Ryf of Switzerland celebrates winning the 2015 IRONMAN World Championship presented by GoPro on October 10th 2015 in Kailua Kona, Hawaii. (Photo by Delly Carr/IRONMAN via Getty Images) IRONMAN Triathlon consists of a 2.4-mile (3.86 km) swim, a 112-mile (180.25 km) bicycle ride and a marathon 26.2-mile (42.2 km) run. IRONMAN is considered one of the most difficult endurance events in the world.