Mile 2.9 is a slap in the face. You turn left down a steep, tree-lined hill with a clear view of the finish and lean, gaining speed, clearing a log hurdle – and then, at the bottom, you're forced to come to an immediate halt. There, precisely 30 feet from the finish line, is a 20-foot-long pit filled with a mud slurry made from potting soil. There is barbed wire hung taut over the pit, forcing the runners – now waders – to dip low enough to get the liquid mud-manure precariously close to their mouths. Some brave or clumsy souls submerge completely. The look of disgust, discomfort, determination, and finally relief, is painted on faces. And then, you earn your medal.

You just finished the Warrior Dash, which is the most popular of a new rash of obstacle races (known to many who run them as "mudders") and which expects to host some 1 million people this year at 65 events around the world. It's a competitive three-mile run – a microchipped race traversing muddy trails, 30-foot-tall wooden obstacles, cargo nets, slides, and balance beams (and, in the case of the recent Maryland Dash in which we participated, around and over the jumps of a motocross track).

But, always, the race ends with that liquid slap of mud in the face, The Pit. The Dash is not as difficult as races like Tough Mudder (the second biggest mudder featuring 12 miles of run-walking over ski slope–grade hills), nor is it all that harrowing. The terrain is hilly, but not mountainous, and the obstacles are manageable for anyone who can do a few pull-ups. And while there's nothing here that's any more strenuous than your weekend 10K road race, the Warrior Dash nevertheless generates an atmosphere of we-just-survived-a-war camaraderie everywhere. Muddy friends, arm-in-arm, stream out of the finish line all day – there are waves of about 500 runners every half hour – and they're chatty, sharing stories of their slips and falls, lost shoes, and favorite obstacles as they're hosed off by the water trucks, or grabbing their free beer at the tent.

Looking back, there was something special in that mud, covering us from chin to toe – it smelled of dirt and farm animals, but also of accomplishment. For 2012, 39 races will be held from June 2 to November 10 across the country, including in Oklahoma, Ohio, Nebraska, Pennsylvania, Indiana, New York, Oregon, Louisiana, Las Vegas, California, Texas, and more. [$65–$75; warriordash.com]