Entrants wearing fancy dress and others wearing little clothing at all were among those taking part in the Tough Guy challenge at Perton, south Staffordshire. All competitors must sign a 'Death Warrant disclaimer' before taking part.
Those courageous enough to enter the event, which incorporates an Army-style assault course, are advised to undertake "cold water training" beforehand to guard against the threat of hypothermia.
Open to individuals and teams, the event is described by its organisers as a "uniquely fear-ridden" test of both body and spirit.
The biannual event to raise cash for charity challenges thousands of international competitors to run through a gruelling set of 21 obstacles including water, fire and tunnels after a lengthy run at the start.
On the event's website it says: 'The event is uniquely fear ridden and you need to be fit in both body and spirit to survive the ordeal.
'You will not be alone, thousands will be by your side. There you will find the true spirit of Tough Guy.'
Contestant's point of view (2008)
ESPN review of the Tough Guy challenge
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