I heard about this and all that I could think about was how much it would hurt. Basically a couple of guys climb up a mountain. When they reach the top they put on thick gloves, knee pads, elbow pads, and helmets. Once they are all equipped to begin their race they start. The guys run as fast as they can down the mountain and don't care at all if they fall or not, basically it's a free for all do whatever you want kind of race down a mountain, the only way to cheat that I know of is to literally take hold of another runner and pull them back. This is not one of those things that I recommend doing because it is very dangerous. Anybody ever been mountain tumbling? I most certainly have not.