Some athletes are just plain hard to please. Take mountain bike riders, for example. You'd think traversing terrain that might cause a tank commander to rethink his route would be a sufficient challenge. But for people who compete in the Texas State Championship Sprint Adventure race series, risking life and limb on two wheels is clearly not enough. The brainchild of Troy Farrar of Houston's Terra Firma Promotions, the June through September series consists of seven races held on courses in Houston, Dallas, Oklahoma City and New Braunfels. The competition is open to two-person teams that must endure a seven- to ten-mile mountain bike race, followed by a two- to three-mile trail run before canoeing for a couple of miles. The frequently brutal race is a true test of teamwork and tenacity, and the best part is that proceeds benefit Texas Wildlife Rehabilitation.