In the 11 years I've been doing naked yoga, it's never been sexual. Maybe I've seen a half dozen erections in that time period. Everyone is busy concentrating on yoga.
Agreed. I did it for many years and only saw a few. Only got a bit hard my first time when fairly early in the session the instructor picked me to demonstrate the wheel pose. He helped me fine tune my positioning (from the opposite side from the rest class) as I maintained the pose. With that particular pose, I felt like my penis was on display, which caused me to start to get aroused. It faded soon enough after everyone else got into the pose and wasn't a big deal