Tough Guy claims to be the world's most demanding one-day survival ordeal.
The annual event to raise cash for charity challenges thousands of international competitors in a cross country run followed by an assault course consisting of obstacles including water, fire and tunnels.
First staged in 1987, the Tough Guy Challenge has been widely described as one of the hardest races of it's type with up to one-third of the starters failing to finish in a typical year. (AP/Reuters)
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