I recall an event many years ago when I was a member of the gay nudist group NEWDimension based near Darwen. There was an event being held at what I would call a bit of run down leisure centre, no mod cons, just an old fashioned swimming pool, not quite the Olympic size one finds these days. An old municipal one in Bolton.
In this building was also a gym and a sauna. Myself an few others tried the gym side, and I did find it quite exhilarating to exercise without the hindrance of clothing. I do think there should be more options for male only nude exercise events in gyms. I am sure there are places that do hold these, but more likely to be in London than up north in Yorkshire.
Of course, it doesn’t matter which form of exercise one does, the penis will show his presence: an erection. In an all male environment, this is a delight I am sure.
I have recently made contact through a nudist website a naked personal trainer, and intend to begin exercises to get myself in shape. One to one instruction would be beneficial. Even so, I would attend a more formal gym where one to hold male only nude events. Bring it on!