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Last year, more than a million people participated in obstacle-course races like , , , and . These events market misery to the masses—requiring entrants to navigate ridiculously punishing courses of hills, mud, water, ropes, walls, and even, as the Tough Mudder website boasts, “electric shock and fire.”

Think of them as hyper-intense versions of the multiday adventure races of yore, the Eco Challenge and Primal Quest, perfect for time-crunched type A's who can relate to the Tough Mudder mantra “marathons are boring,” but need to be back at their desk on Monday morning. 

Or, in some cases, back at the playground. 

Several big race series, including Muddy Buddy, Spartan Race, and relative newcomer  (now in its third season), are offering tamer, if no less slimy, obstacle races for mud junkies as young as four. Merrell's �����ԹϺ��� Kids races, held in conjunction with its adult events, are shorter courses riddled with tyke-sized obstacles a lot like the ones you’ll find on the school playground: balance beams, tire hurdles, and wall climbs—capped off with a belly crawl through a giant gloppy mud pit just before the finish line. It doesn’t take a huge stroke of marketing genius to reason that kids, who generally will seek out any and every possible opportunity to get as filthy as possible, would eat this stuff up.

Last year, more than 2,500 kids and nearly 40,000 adults participated in Down and Dirty races. “It ties directly back to our mission to get more people—big and little—outside,” says Craig Throne, Merrell's vice president of global marketing. “From kids on their father's back swimming through the mud pit, to hurdles and slippery shampoo wall climbs—the more we can do to make the outside fun for families, the more successful we will be in our goal of increasing outside participation.”

There are eight more Down and Dirty �����ԹϺ��� Kids race dates in major cities around the country this summer, starting in Chicago this Sunday, May 20, and ending in Sacramento on October 27-28. Mini Muddy Buddy events are scheduled for six dates, starting in Atlanta on June 9 and ending in San Jose on September 30. The only thing missing: free babysitting so parents can torture themselves on the adult course first and then cheer on their mud babies (though if your kid is age 4-6, sorry to say, you'll be making a mandatory second lap through the mud pit).

Check out , , and  for complete schedules and details.

—Katie Arnold