Kim Kardashian And BFF Jonathan Cheban Bust Their Butts With Celeb Trainer Tracy Anderson

When you want the best of the best when it comes to fitness ... celebrities like Madonna and Gwyneth Paltrow will tell you that Tracy Anderson is your girl.

While in Miami filming their reality show, Kim Kardashian and her BFF Jonathan Cheban worked out their bodies at Body Soul Miami with the celebrity trainer.

Looks as though Ms. Kardashian was proud of her booty ... skipping undies for the workout. But even more impressive, Tracy's body after giving birth just a couple months ago. Whew!