So you think that monkey bars are for kindergarteners, and that rope climbs belong in second-period gym classes? Think again. Tough Mudder knows that the easiest looking obstacles can cause the biggest trouble. Each course is designed to test your physical fitness and your mental strength — that means not only pushing your body to the max, but conquering your worst fears: heights, frigid water, electric shocks, fire, you name it. We talked to Tough Mudder’s course design manager Nolan Kombol, who broke down the obstacles that’ll most likely trip you up. Study up — and never let your guard down.