Much like the Tough Mudder, the Spartan Race series calls itself "the toughest event on the planet," and offers plenty of options for testing your physical and mental limits.
Courses are three miles, eight miles or up to a dozen miles long. Challenges include leaping over hot coals and traversing a rope over a river. There are even kid versions. But get your game face on first: According to Outside magazine, only 60 percent people who start the 12-mile race end up finishing.
"There is fire, mud, water, barbed wire, and occasionally Hell on Earth," explains the Spartan website's FAQ, which intentionally keeps the details vague. "There WILL be obstacles to catch you off guard. Curve balls, so to speak. Get over it."