The morning of the Warrior Dash 5K race in July, David McIntosh nearly made the mistake of wearing nice running shoes.

“At one point we were crawling through mud almost up to our armpits,” says McIntosh, 33, who was a triathlete at the time. “Mud the consistency of cement.”

Tough Mudder participants crawl through mud under low wires in an obstacle called the Kiss of Mud. (Photo courtesy of Tough Mudder by Jack Megaw)

Rebecca Kelley, a 22-year-old who ran the event with McIntosh in Mt. Morris, Mich., jumped over a 3-foot tall fire at the end of the course after running 3.1 miles and navigating a dozen other obstacles.

“I’m really glad I don’t have leg hair because I would have caught it on fire,” she says.

Though jumping over fire and wading through mud might not seem like ideal weekend activities, obstacle runs like these are spreading throughout North America, attracting a diverse collection of competitors, from non-athletic types to marathoners and body builders. The courses, largely based on forms of military training, vary in distances, but are always peppered with obstacles.

The “adventure races” challenge traditional forms of exercise, being not simply about self-improvement or sculpting the body through running or weightlifting. Competitors feed off the excitement of surviving the obstacles, which are inspired by some of the worst that military minds created.

“Our constant promotion of the military being a good thing has translated into a way of marketing a fun event,” says Becky Beal, an associate professor of kinesiology at California State University, East Bay.

Beal notes that how we frame fun is important, and, although the races appeal to serious athletes, these events combine boot camp fantasies with an overt party atmosphere. Many races require large fields to accommodate parking and the obstacle courses, and some span weekends, with live music, costumes and beer. One organizer said a race team carted a mini-fridge over the course, stopping for refreshments along the way.

The three largest obstacle runs — Warrior Dash, Tough Mudder and Spartan Race — are offering more races this year, as the lure of the unusual has attracted many who might never have signed up for a traditional race.

The 5-kilometer Warrior Dash will have at least 47 races and is expecting more than one million competitors in 2012. The longer Tough Mudder, generally 10 to 13 miles, plans 30 to 40 events throughout the United States, Canada, Britain and Australia. The Spartan Race, which offers races of varied lengths, held 27 events last year and has 37 planned for 2012.

“I hate running four laps to make a mile,” said Rod Partow, 23, who completed a Warrior Dash in Southern California last year with a group of college friends. He trained enough to “not get embarrassed,” meaning a few laps around the block once or twice a week. “For one friend, it kind of opened the door to running. He signed up for another marathon or triathlon,” Partow says. “But afterward I realized I paid $70 to run three miles.”

Partow doesn’t sound like he’ll be entering many more races, but he boasted when describing his costume: “I shaved a Viking helmet in my chest hair.”

Tough Mudder participants climb monkey bars over a pool of cold, muddy water. (Photo courtesy of Tough Mudder by Jack Megaw)

Though intense training may not be necessary for the shorter 5K races, some preparation is helpful for the longer 10- to 13-mile events.

Peter Isip, who operates three gyms in New Jersey and New York, ran a Tough Mudder last year and has since blogged training tips for the race. “The blog derived from the first time I did it,” he says. “It was a horrible experience.”

Isip says that core and upper-body strength can bring ease to crouching under obstacles or lifting yourself from the ground. And whenever a race comes to town, his gyms get busy.

Aaron White, the founder of the TNT Shrinks gym in Kent, Ohio, took a Warrior Dash course map and reverse-engineered his own training program.

“We would run 3 to 4 miles and would set up stations,” White says. Every quarter-mile or so he planned an alternative activity, like pushups or lifting logs to develop the strength needed for an obstacle.

Some race obstacles are as simple as the mud McIntosh endured, while others are more inventive, like jumping into a Dumpster filled with bright green ice water or navigating a steep hill while being sprayed by high-pressure hoses.

Michelle Prieboy, a 27-year-old exercise physiologist in Mokena, Ill., who ran a Tough Mudder last year, remembers one obstacle, a 12-foot wall that competitors had to pass over without the aid of ropes. “Some of the really strong guys couldn’t jump high enough to grab the top with their hands,” she said. “So you get two people, kind of like a cheerleading move, to cup their hands and put their foot in it and hoist them up.”

After the November event in Indiana, a part of Prieboy’s traditional running crew formed a group called Randomocity, which focuses on running obstacle races and has about 100 members. The group has a website, sponsors, T-shirts and bumper stickers.

“This, for a lot of people, has been a really life-changing experience,” she says.

Kelley and McIntosh, who ran in Michigan and now attend different graduate schools in New York City, trained less than they had planned, but, being somewhat active people, had little trouble with the course. It did not seem that they were alone. “You would have people who look like it might have been their first time off the couch in a while,” Kelley says. “And there were people who looked like they’ve been running triathlons and going to the gym every day.”

After the race, McIntosh left his old, waterlogged footwear to be recycled on one of many six-foot-tall piles of muddy shoes. Kelley, after rinsing in a 40-degree shower from a water truck, still couldn’t seem leave the race behind.

“Driving home we were still disgusting, we smelled terrible,” she says. “I, halfway through, touched my hair and felt something hard. And it was most definitely a dead beetle that was in there from the mud.”

Email: bed2118@columbia.edu