From Time.com: Chess-Boxing Hits it Big
The matches work like this: competitors alternate between three-minute rounds of boxing and four-minute rounds of speed chess with one-minute breaks in between to get the gloves off and hunker down at the chess table.
The winner is determined by knockout, checkmate, or referee decision.
This is pretty funny. It seems like it would favor boxers who play chess rather than the typical chess players who might box.