19. Tired Yet?
Bringing in some of the biggest rubber tires around, Tough Mudder laid out a field of tired you have to tiptoe your feet through carefully. Climb a small, five-foot hill of rubber tires and cross the 40-foot tire field. This is a good obstacle to take your time and catch your breath, but run with caution because unevenly spaced tires sit at uneven heights so you’ll trip up.
Hint: When you’re running through Tired Yet?, use your core and pull your legs and knees high into your chest to ensure full clearance of the tires.