A striking characteristic of Greek athletics is that athletes exercised nude. The Greek word for sport, 'gymnastics', is even deduced from the adjective 'gymnos', which means 'nude' or 'lightly dressed'. The custom of exercising naked began in the sixth century BC. Before, athletes wore a loin-cloth, like sumo-wrestlers today. Thucydides and Plato agree that the custom of wearing a loin-cloth disappeared shortly before their time (the fifth century BC). On vases of the sixth century athletes are sometimes still depicted wearing them.

Pausanias explains the habit of exercising nude with the story of Orsippos. This athlete from Megara is told to have won the stadion after losing his loin-cloth while running. The other athletes then followed his example.

Modern antropologists consider athletic nudity a remnant of old hunting rituals. Hunters wore no or few clothes to spread as little odour as possible, for odours cling in clothes. Because this way of hunting was successful, it continued as a ritual in athletics. In any case nudity had no negative connotation for the Greeks.

In the ancient Near East nudity was a sign of defeat and disgrace, because prisoners were carried along naked in the triumphal march of the king. For the Romans public nudity was offensive as well. A gentleman could not show himself naked in public, except in the baths.

The Greeks on the other hand were proud of their naked bodies. They considered public nudity as a way to show their superiority over other people. According to some scholars, this superiority lays in the ideal of self-control: the gymnasion was a source of sexual excitement for the athletes themselves. By self-control they could look calm and balanced. To make sure they controlled themselves, some athletes tied up their genitals during exercise. This practice is called infibulation.