The 36-year-old beauty stars as Maureen, the wife of boxer
Billy 'The Great' Hope, in the movie and has revealed she used her time on set to perfect her boxing techniques, reported USA Today.
"I figured Maureen would understand boxing really well. She'd make it her business to know it. Jake (Gyllenhaal) came and watched me box in the ring," McAdams said.
"I practiced. I wasn't fighting. I definitely wasn't fighting. I just tried to pick it up. Nowhere near the extent that Jake did. It was an excuse to sweat and get in shape. It's a total head to toe workout. You do one three-minute round and you're toast.