Ben Holmes was poised at the starting line of the Boston Marathon in 2000 when he had a realization: "I hate this." Not the running, exactly, but the noise and the crowd and the abuse his body took pounding 26.2 miles on cold, hard concrete. Back in Kansas City, the seasoned runner already had abandoned the streets in favor of training on local trails; when he got back from Boston, Holmes became the founding member of the Kansas City Trail Nerds and put together an e-mail group to coordinate group runs in off-road locations. It's true — high-tailing it over rocky, muddy, root-covered paths requires a lot more stamina and strength. But Holmes and his comrades say the payoffs — less wear and tear on the joints, more peace and quiet and communing with Mother Nature — outweigh the pain. More runners are getting down and dirty, too. So many, in fact, that the Nerds started a series of local trail races last year. Thus far in 2007, the wild events — with names such as the "Fat Ass 50K" and "Dude, Where's the Trail?" — have doubled in participation. To get your ass in gear, the Nerds host as many as six training runs each week at nearby locations. But be sure to remember your headlamp for the 8:30 weeknight runs. These Nerds like to stay up late.