The sport
What is chessboxing?
The hardest game.
Chessboxing is a hybrid sport that alternates rounds of boxing with rounds of speed chess. You play a round of chess, box a round, then go back to the board, and it repeats until someone wins by checkmate or knockout.
It asks two very different things of you at the same time. You need the composure to think clearly when you are exhausted, and the fitness to keep fighting while you think. Not many sports ask for both.