Picture this: you’ve just belly-crawled under dangling live wires, not escaping without sizzling electric shocks pulsating through your muscles. Ahead of you, after a 100-yard dash through muddy sludge, monkey bars slant upwards, covered in mud and butter—a near impossible bridge over frigid water. It’s mile six of 12. You’re scratched up. You’ve swallowed mud (and who only knows what else). You’re tired as hell. The last thing you want to do is rub your hands and hope for enough friction to keep you airborne for 0.7 seconds while you wildly swing one-armed for the next rung. But a “Come on man, go for it!” call from your teammate makes you jump. For a glorious second, you think you got it. Then you plunge seven feet down into a muddy pool of icy water. Frigid waves swamp your brain. Your waterlogged muscles scream in protest. But for some reason, you keep going. Why? Because it’s Tough Mudder. That’s why.

Over 10-12 miles, runners tackle 25 military-style obstacles through mud and fire climbing hills and ropes. The challenge can quickly become hell. But it’s also the world’s fastest growing adventure event, which poses the question: are people getting crazier? The answer: without a doubt. Here are 20 of Tough Mudder’s most badass obstacles—a preview of what you’re up against. Want to taste what you see? Think you’re tough enough for a Tough Mudder? Here are here are 7 signs to see if you've got what it takes.