Still reeling from the record breaking runs of Usain Bolt, the heroic standoff between Lee Chong Wei and Lin Dan, and other magnificent world-class performances? Extreme adrenaline junkies always love a challenge, especially ones that pushes the human body to spectacular levels of mental and physical endurance. Though the truth is there are more insanely tougher activities out there other than the Olympics. Here are seven of the world's toughest sporting challenges...