Vince Vaughn gets fit on the set of The Watch

Movie star Vince Vaughn embarked on a health kick on the set of new comedy The Watch and tried to persuade co-stars Ben Stiller and Jonah Hill to join him.

Stiller reveals his pal would start the day with a healthy green veggie smoothie and work-out in between takes.

He says, "He got everybody drinking these green drinks and he was into the P-90X work-out thing... It works, it's great, my wife did it for a while and Vince would have us do, like, spontaneous plyometric exercises on the set in between takes.

"It's all about muscle confusion... confusing your muscles so they get angry and grow."