Barbed wire. Mud pits. Jacked "gladiators" armed with cudgels. Obstacle racers face a lot of stumbling blocks on their way to the finish line. The sport, which pairs a footrace with Navy SEAL-style challenges, is hitting critical mass in this country, with thousands of athletes signing up for mud-caked events like the Spartan Race, Tough Mudder, and Warrior Dash. For a primer on the best gear for the sport, we interviewed two champion racers: Hobie Call, the most successful Spartan Racer of all time, and Margaret Schlachter, a Vermont-based athlete with top finishes in races like the Warrior Dash and Tough Mudder New England. This is the gear that helps them get to the podium.