FOR MANY OF US, sumo wrestling is a shoving match between two enormous men in diapers and top buns. They’re considered “athletes,” sure, but their only job is to be fat and to slam into each other. Yes, they’re burlier than an NFL linebacker . But top sumo wrestlers also have the speed off the block of a sprinter, the flexibility of a yogi , and the mental stamina of a Trappist monk. Professional sumo doesn’t have weight classes, meaning a 600-pound wrestler can face off against someone 200 pounds. Still, it’s not enough to be the heaviest guy in the ring. “Most people don’t understand that sumo wrestlers are very athletic,” says two-time champion Byambajav Ulambayar, who goes by Byamba. He’s originally from Mongolia and is one of the most recognized wrestlers world- wide. “Pro sumo wrestlers are quick, flexible, strong, and quite tough,” he says. A traditional sport of Japan is finally getting its due this side of the Pacific. USA Sumo, the sport’s biggest booster in the States, h