The word gymnasium comes from the Greek word gymnos which means "naked". Greek gymnasium was a place where naked or nearly naked athletic activities such as gladiator games would commonly take place as well as classroom lectures and philosophical discussion. Given the mild pleasing climate in Greece, no clothing was needed and scholars' and teachers' aim was to establish a balance between the mind and body.
Nudity has religious and philosophic foundations in Ancient Greece. Less known fact when compared to the fame of Greek literature, law, art or politics.
Archeological evidence points out the many artefacts depicting fully naked performers as well as labourers in the fields. Socrates was very much in favour of nudity and would see it as a form of honesty.
After women's rights movement, also ladies comfortably performed nude during games, just as men did. Nobody thought of it as shameful, disrespectful for Spartan women to be naked in public dances and processions. Nor would anyone perceive it as a lustful experience. At the end nudity entered even the Olympic Games and became an integral part of it till 393AD when they were banned as pagan games by the Roman Emperor Theodosium and had not revived for another circa 1500 years.
Tantric style nude massages have as well existed for millennia, both for relaxation, therapy, energetic release as well as sexual energy liberation and renewal.
Source:
Therapy, Nudity and Joy: Therapeutic Use of Nudity Through the Ages by Aileen Goodson, PhD. Chapter Nudity In Ancient To Modern Cultures. 1991, Elysium Growth Press.