"If rattlesnakes, cottonmouths, alligators, scorpions, wasps, mosquitoes, chiggers, horseflies, spiders, palmetto stumps, swamp, sugar sand, sawgrass, briers, wild pigs, or World War II ordnance bother you, go back to Yahoo! The rest of you, listen up!" Welcome to the opening lines of the Website of Club Scrub, a group that has spent nearly every Sunday morning for the last year clearing a single-track, mountain bike path through the dense pineland of the 11,500-acre Jonathan Dickinson State Park. Hard-core stump-jumpers have been coming to the former Camp Murphy army base, just north of the Palm Beach line in Martin County, since the early 1990s. But it wasn't until Mark Nelson was named park manager later that decade that work began on the long-awaited trail. As former top dog of the Oleta River State Recreation Area, a mecca for mountain bikers in northeastern Miami-Dade County, Nelson had experience with the lunacy of the off-road set. So far, with Nelson's support, Club Scrub members have cleared more than five miles of trail. They hope to have an additional ten opened before year's end. Because the trail is a work in progress, each visit brings a new surprise. In late February, for instance, bikers could take a roughly ten-foot-high jump off a concrete pad that was left behind when the army camp closed in 1944. Marked with a red sign warning, "Experts Only," the jump proved to be too extreme, says Club Scrub president Steve Bucina. "No one can do it," he adds. "We'll probably put a ramp down the back side." But even without such practical adjustments, the trail offers far more than your average trek through Florida wilderness. It winds around the remains of barracks and other buildings once occupied by servicemen who were sent to the outpost for jungle warfare and radar training. Some hills are actually old bunkers. As you pedal through the place, ponder this question: Which is worse, training in South Florida heat or fighting a war?