I recently heard American football described as the 'quintessential American sport,' because it is both violent and legalistic. The U.S. National Football League rule book takes nearly 200 pages to outline proper behavior for the helmeted giants who contest matches at the sport's top level.
Sumo wrestling, by contrast, is the quintessential Japanese sport, also contested by large men, but governed largely by tradition -- its rulebook runs to just half a page and is mainly limited to banning punching, eye-gouging and hair pulling. Basically the loser is the first competitor who touches anything outside the ring or contacts the ground with any body part other than the soles of the feet. It's as simple as that.