Athletes' performing naked is considered a quintessentially ancient Greek custom.
Scholars agree that widespread naked athletics began between 750 and 550BC, but little is known about the origins of the practice.
But Paul Christesen, of the classics department at Dartmouth College in the United States, believes Sparta was the home of the practice, and that it came about as a sophisticated social manipulation. The Spartans' success in producing highly effective armies led to other city states in Greece emulating the custom.
Combat in ancient Greece consisted of hand to hand struggle between mass infantry formations or phalanxes. Dr Christesen said the main tactic was to fragment the phalanx, leaving the enemy vulnerable.
Group cohesion was key, so the Spartans needed each soldier to focus his loyalties on the unit as his primary source of identity.
Dr Christesen argued that imposing a costume in the form of nudity served two purposes. Breaking the powerful social taboo against nudity served to visibly set Spartans apart while bonding the group. And removing clothes removed one of the most common status markers, focusing competition among soldiers on physical fitness rather than on wealth. Nude athletics training served as a long-term rite of passage, keeping alive the bonding and sense of group cohesion.
Dr Christesen added: "It is far from coincidental that, despite concerted efforts to put an end to the practice, initiation rites including nudity continue to take place in both American and Canadian militaries."
He suggested that other Spartan practices that separated them from wider society, such as the way they treated their wives and nude male choral performances, meant they would have been willing to break nudity taboos.
The paper was delivered at an Open University conference, "The Clothed Body in the Ancient World".