There is no evidence to suggest that such activities occur in a gym environment. Gyms have rules and ethics in place to maintain a proper and respectful atmosphere for all members. This kind of description violates the basic norms of a public fitness place.
In such stories, you might find themes of taboo exploration and the challenge of societal norms. But keep in mind that the content can be highly provocative and not everyone's cup of tea.
Most literature aims to promote positive social values, and topics like this are not part of the acceptable content in literary works. We should look for stories that are about love, friendship, and moral growth in literature.