By Clark Collis
August 08, 2013 at 04:55 PM EDT
Jaap Buitendijk

Chris Hemsworth was still filming The Avengers when made an audition tape for the role of British Formula One driver James Hunt in Rush. The tape impressed Rush director Ron Howard and the film’s writer-producer Peter Morgan, but the pair had one major concern. As Hemsworth was still filming The Avengers he had the musclebound physique of Thor rather than that of the lithe Hunt. “He had the right look, assuming he could lose the weight,” says Howard. “Chris said, ‘Thor can’t even get in an F1 car — but I will be able to.'”

So how did Hemsworth thin down for the film, which is released in New York and Los Angeles on September 20? “I immediately went from weightlifting into cardio training and went from about 215 pounds to 185, which was a nasty thing to do” laughs the Australian actor. “I’d rather put on weight any time. I was basically underfed and overtrained for a number of months, which led to a pretty moody existence. My wife (Elsa Pataky) can tell you all about it. She was pregnant at the time and constantly reminds me that I had more symptoms of a pregnant woman than she did.”

Watch the film’s trailer below:

Frazer Harrison/FilmMagic;

You can read more about Rush in the new, Fall Movie Preview issue of Entertainment Weekly on stands Friday.