The gym offers clients the choice of four celebrities with larger than life posteriors: Beyoncé Knowles, Kim Kardashian, Kylie Minogue, and - the subject of more recent hubbub - Pippa Middleton.
Trainers wearing shirts emblazoned with the names of their respective celebrities lead the six-week "Yummy Bummy" classes, which cater their techniques to customers' desired goals. The Pippa class incorporates more pilates, while dance and toning exercises help achieve Beyoncé's more athletic and rather ample rear.
"I would say it's probably closest to a publicity stunt," said Herbert Schmale, a personal training manager at the Equinox fitness chain, of Gymbox's promotion. "But can it happen? Are there certain exercises you can do to target areas differently? ... Of course."
"Everybody's body is built differently," he added, pointing to the role of genetics in determining people's body types.
What do you think -- whose caboose would you sweat over?
Meanwhile, catch the video below to hear what Kim Kardashian has to say about her infamous posterior.