Running is a pastime enjoyed by many. But while a jog in the park is enough for some, there are others who happily test the very limits of their physical and mental endurance by embarking on punishing leg-screaming, blister-inducing ultra trails in remote corners of the world.
If you're one of those people who revel in adversity and drink adrenaline for breakfast, you'll be turned on big time by this list of some of the world's most arduous running races. Click on!