Jennifer Aniston and her trainer had to come up with unorthodox ways of working out as the actress toned up to play a stripper in her new movie We're The Millers because knee surgery made gym sessions difficult. The former Friends star teamed up with a fitness instructor called Jason, who was also an animal trainer, to help her get trim for the role and she admits work-outs were very painful and frustrating at times. Aniston explains, "I was doing stuff... I never want to do again, just work-outs that are really, really hard. "I had knee surgery right before I had to start all this training, so it was doubly hard to do because you had to figure out ways to work-out without using your knees, which is impossible, especially when you're doing, like, deep squats around a pole."