Rachel McAdams doesn’t play a boxer in her new film Southpaw, but her on-screen husband–played by Jake Gyllenhaal–does, and she said she dove deep into her role in order to play the character right. For McAdams, that included taking up boxing and practicing on set.

“I figured Maureen would understand boxing really well. She’d make it her business to know it. Jake came and watched me box in the ring. 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,” McAdams said.

It’s not as though Rachel is in bad shape; her character on the hit HBO show True Detective has to be fit in order to chase the bad guy and keep up that dangerous knife habit she has. And speaking of knives, the actress isn’t averse to using them in real life, either. McAdams said in an interview recently that after being diverted to a shady hotel in Costa Rica while there on vacation several years ago, she slept with a knife to feel safe.

“I was kind of stupid. I got off the flight to Costa Rica and got on a little four-seater Cessna plane and was dropped in the middle of the rainforest as the rain was pelting down. I got in a cab with no doors and asked the driver to take me to this hotel, and he told me in broken English it had burned down, so I wound up in a place costing five dollars a night. There was a cold shower and guys pounding on my door all night. I slept with my Swiss Army knife in my hand, thinking: ‘I’m going home tomorrow!’ Of course, things always seem worse in the night,” Rachel McAdams said.