Darkness rapidly sets in on Wyandotte County Lake Park, and the excitement is building.

It's a few minutes past 8 p.m. on a Friday. The trail has been marked. Last-minute battery checks are conducted on flashlights and headlamps. Shoelaces are tugged a little bit tighter as Ben Holmes, co-founder of the Kansas City Trail Nerds, gives a few last-minute instructions.

"There's some shoe-sucking mud holes out there," Holmes says of the course, noting some runners likely will lose a shoe or two and have to stop to dig it out.

Moments later the group of about 80 runners is off. Amid a flurry of laughter and cheers, they hurdle a ditch, tiptoe around mole holes, charge up a hill and disappear into the woods on a 10-kilometer course.

With headlamps glowing like lightning bugs, they zig-zag through a maze of mountain-biking trails, dodging loose rocks, trees and low-hanging branches while tramping through mud - lots of mud.

About 45 minutes later the first runner -Gregg Buehler, an Olathe resident and cross country coach at Blue Valley North - emerges from the woods, hops back over the ditch and crosses the finish line back where the race began. More than an hour after Buehler finishes, the last of the runners completes the course. All are breathing hard, smiling and laughing. All wear sneakers that are much filthier than they were prior to the race.

"This is a back-to-your-youth type of thing," Buehler says with a laugh. "You get muddy. About a month ago I did their Psycho Wyco (Psycho Psummer 50K Trail Run) thing out here and I got poison ivy, I got muddy, I was pulling ticks off me, all that other stuff. There's probably not many 37-year-olds that can get away with doing that and save their dignity. This is something that keeps you young."

THE MOVEMENT

The Trail Nerds unofficially began in 2000 when Holmes, Trail Nerds co-founder Kyle Amos and a few other friends began hitting the trails around Kansas City. They coordinated their runs via an e-mail list. Eventually in 2004 they decided to make it an official organization. They launched their Web site and organized a 50K race.

"We had like 44 people that day and 21 finishers," Holmes says, adding, "The rest are buried out here."

The race was tough, especially for many of the trail-running newcomers, but a year later they realized they were onto something.

"The next year we had 400 (runners)," Amos says. "It was crazy."

Today the e-mail list includes more than 400 names. In February they played host to a race that had 440 runners. The bulk of the Trail Nerds hail from Wyandotte, Leavenworth and Johnson counties, but some drive in from Lawrence, Topeka and Missouri just to run.

Despite having so many members, Holmes doesn't refer to the group as a club.

"It's less of a club and more of a movement," he says.

BETTER THAN ROADS

The "movement" Holmes refers to may represent the drifting of runners toward backwoods trails and away from roads and paved paths.

Sure, some of the Trail Nerds run on roads in addition to trails, but many have downright disdain for smooth surfaces.

"I don't like running on roads at all," says Coleen Voeks, a Kansas City, Kan., resident. "If I don't have time to hit the trails and I actually have to run on the road for a day or two, I feel it. I'm sore. I hurt."

The pain - or lack thereof - is one of the major reasons runners cite in their preference for trails.

"I think they say it's 30 percent softer, and it's 100 percent more fun," says Sophia Spencer, a Topeka resident and recent Boston Marathon finisher. "If you're hurt on the trails it's because you fell and you were probably having a good time."

Part of the fun of trail running is the cushion that the softer surface provides for the joints, but there's also the fact that a trail is an obstacle course. Runners encounter open fields, wooded areas, hills, rocks, creeks, fallen trees and more. It's a mixture of cross country and Red Bull.

Holmes once crafted a course called "Fester's Wander" that is named for his former dog.

"It was a mile of us following a deer trail, losing a deer trail and finding a deer trail," he recalls.

MUD BABES

The Trail Nerds may have been a bit of a boys club when they began, but there's a good mix of male and female participants now. Just like the men, the ladies aren't shy about tramping through a mud puddle and turning their white sneakers dark.

During the Brew-to-Brew run in March, Spencer coined the nickname "Mud Babes" for the Trail Nerd ladies. Voeks had a friend design a T-shirt that conveyed both style and attitude.

"There were so many girls that ran that we were like 'Oh my gosh, what a great thing," Voeks says. "We all kind of bonded, so it was like 'yeah, we'll be the Mud Babes!'"

Whether it's a training run or an actual race, Mud Babes shirts are prevalent. They've even caught the eye of members of other running groups, both for their racing tactics and sense of humor.

"We were doing the Summer Psych (run), and we were doing the first loop and there was all this mud," Spencer recalls. "And I was like, 'Coleen, come back here,' and I painted a little muddy heart on her. And there was somebody who lost their shoe, and she was like 'I see why they call it Mud Babes. Now can I buy the T-shirt?'"

ANYBODY CAN DO IT

Whether a Trail Nerd or a Mud Babe, trail running is an activity that is accommodating to just about everybody. There are older and younger runners, parents and children. Some race, and others walk or jog at a more leisurely pace.

"We get a little bit of everything," Amos says. "I don't think, if you ask around, most of these people are not your traditional runners. They come from different backgrounds. But it's just different out here because it's different from running on the roads and it's a different group of people too. You tell that when you're hanging around afterward and the conversations here are different, and the competitive side of these runs is a lot different."

For those wanting to trot the trails, location isn't a problem. The Trail Nerds organize between eight and 10 runs a week at Wyandotte County Lake Park, Shawnee Mission Park in Lenexa and Clinton Lake State Park in Lawrence, as well as various other locations around the metro area.

The group is far from exclusive, and welcomes anybody who's willing to get his or her feet dirty.

For those new to the trails, a "trail running for beginners" course is offered on Monday nights at Shawnee Mission Park. For more advanced trail runners, the group organizes races in the area and sends teams to competitions throughout the country. Amos recently placed 10th in a 100-mile trail run in Wyoming that lasted more than 23 hours. Voeks was a nonrunner when she joined the Trail Nerds in September, and seven months later she ran her first marathon.

Although the Trail Nerds emphasize running and getting dirty, the camaraderie of the group is what has helped it thrive.

"It's a good way to meet people, and everybody's really into it," says Amy Hearting, a WaKeeney native who recently moved to Shawnee and joined the Trail Nerds this summer.

Buehler - the winner of the Psycho Night 10K Trail Run - agreed.

"It's a little subculture that's a neat group of people," he says. "They're very, very humble and are out here to have fun. There are people from all walks of life, there's people that walk these things, people that try to do it fast, people that do long ones and short ones, but the social aspect is great. They're just neat, neat people that are a part of this, and you have to be. I think it breeds a lot of humility, so it's a neat sport like that."