Mixed Martial Arts (MMA) in 1963: LeBell chokes out a boxer

Most modern MMA is contested in a fenced enclosure. The UFC's eight-sided cage, the Octagon, measures 30 feet across with a five-foot padded fence, keeping fighters inside and adding a wall that can be used to press, clinch and defend takedowns. Other promotions use a ring or a circular cage. The enclosed space is a strategic surface in its own right: fighters cut angles toward the center, back opponents into the fence to grind, and use the cage as leverage to stand up or finish a takedown.

Fighters compete within a division to keep matchups fair. The UFC runs eight men's classes from flyweight (125 lb) up through heavyweight (265 lb) and four women's classes from strawweight (115 lb) to featherweight (145 lb). Athletes weigh in the day before, often after a severe water cut, then rehydrate overnight. Missing weight means forfeiting a percentage of the purse and, sometimes, the bout being changed to a catchweight. Title fights carry a strict one-pound allowance that non-title bouts do not.

Ways to win: KO, TKO, submission, decision A knockout ends the fight when a legal strike renders an opponent unconscious. A technical knockout comes when the referee, doctor or corner stops it because a fighter can no longer intelligently defend himself. A submission ends things when a fighter taps to a choke or joint lock, verbally quits, or is choked unconscious. If no finish arrives, the judges' scorecards decide the winner. Fights can also end in a draw, a disqualification for fouls, or a no-contest.