The fighting contests, or ‘heavy sports’, as the Greeks called them , were among the most popular events of the games. There were three different kinds of combat: wrestling, boxing and pankration. In each of these three sports, the athletes fought naked.
An important difference with today is the absence of weight categories. The heaviest man often had the advantage. Some authors, like Euripides and Galenus, nevertheless warn of overweight, which slowed down the athlete. There were age categories: boys fought in a different series. A second important difference with today is the absence of rounds. The athletes kept on fighting till one of them lay knock-out, or gave up. Therefore endurance was essential.
Each match was followed by an umpire, who punished those who offended the rules with a whip or a stick.
The Greeks considered combat more than just a sport, it was an essential part of education. They practised it in the gymnasion and the rich even employed private trainers.