The races are certainly a novelty, and most novelties eventually wear off. But organizers insist they've tapped into something deeper, more primitive and elemental.
"Humans have done this for 900,000 years. We didn't go to Starbucks. We went out and hunted food," says Joe Desena, co-founder of Spartan Race. "When we put people in this environment, they feel at home because deep down inside this is what we did for so long."
Alex Patterson at Tough Mudder says that in a world in which "we're never too cold, we're never too hot, everything is just right," people long for a challenge — and a unique experience.
"We are tapping into the idea of experiences as a new luxury good," he says. "You are often advertising who you are through Facebook, and the photos you post on Facebook after the weekend. Think about what you can say at the water cooler the day after. You can spend all day Monday talking about your experience, and people do."
As with any physical activity, there's always the risk of injury, or worse. Two men collapsed in the heat and died while running a Warrior Dash in Kansas City, Mo., last year. And three people developed E. coli infections after running a Tough Mudder event in Scotland last month, according to the Scottish health agency. Investigators are working to confirm a link, according to Tough Mudder spokeswoman Jane Di Leo.
"Hundreds of thousands of people have gone through our courses without a problem. This is the first time that anything like this has ever come up," she said.
Di Leo and officials from other companies say that runners' safety is paramount, with water and first-aid stations positioned along the courses and all applicable laws and health regulations complied with.
Ray and Kate Meehan, a married couple from Philadelphia, did Warrior Dash together and considered it a milestone along their journey to better health.
"I tell my son he can do anything he puts his mind to," said Ray Meehan, 48, who's lost 50 pounds. "I figure if I tell that to him, I better try this."
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