With rise of races like Tough Mudder, extreme fun comes with serious risk

As adrenaline-fueled races have exploded in popularity in a recent years, creating an industry with tens of millions of dollars in revenue, some racers have paid a high price.

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  Tough Mudder, Warrior Dash push racers to extremes [Pictures]

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  Injuries and deaths mount at extreme races across the county [Interactive Timeline]

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  Ellicott City man dies after accident on Tough Mudder obstacle course

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  Injuries after Tough Mudder included heart attacks, electrical shocks