While all this may seem outlandish, Mistress Anna explained that combining fetish play with fitness is just another way to make her clients feel comfortable exercising and working out.
"I've taken the majority of exercises that you see in a normal circuit class and then kinkified them," she told SBS in 2014. "The clients come and see me not to just get fit and get off, I think it's because I really understand them and I allow them to be who they are."
In a recent interview with The Daily Mail, Mistress Anna said her courses are still going strong and getting bigger.
"I still have my original clients who have been with me since the beginning," she told The Mail. "Some of them just want to train in normal clothes but still want me to be stern with them," she said. "I love seeing people have a good time and keep fit."
One of Mistress Anna's clients, a married engineer named Ray who identifies as a submissive slave, told SBS that the workouts were both sexual gratification and self-improvement for him.
"It is a sexual turn on for sure," Ray said. "Mentally there's a certain excitement factor there, physically it's actually very hard work. You start to feel like you're out of your own body, sometimes you feel like you're floating on the ceiling. You don't feel pain like you normally would in normal circumstances."
And hey, as anyone who's done intensive circuit training will tell you, overcoming pain is part of the program. So anything that helps you get through that is probably a good thing— no matter how kinky it is.