Everyone knows Ironman is the King of all triathlons. But a Double Ironman takes the tri-distances to a different level, pushing you to the absolute limit. Take a full Ironman triathlon and double the distance of each event. Yep. That means a 4.8-mile swim, a 224-mile bike ride, and a 52.4-mile run.
While not officially sponsored Ironman, Double Ironman was born from Ironman lovers who wanted to push the King of all Tri’s even further. In other words, if you sign up, don’t expect to have a life outside of training. (iutasport.com)