Scarlett Johansson has portrayed the character Black Widow for over a decade in Marvel’s MCU films. To get into shape for this role (and stay in shape), she works with her personal trainer, Eric Johnson, who has been helping her train since 2009. To prepare for the role, Johnson focused on building strength and functional movement. They treated it like an athlete preparing for competition. Johansson says that before accepting the role in Marvel's Avengers movies she had never stepped foot in a gym, but that now she is stronger than she was 10 years ago. None of this was a quick fix for Johansson, though — it took time to build her strength and fitness for the role. Johnson split her training into three phases, each lasting three to 12 weeks. Phase one focuses on explosive swinging and plyometric movements to improve her reflexes and agility. The second phase is strength training, performing exercises like pull-ups and squats. And the third and final phase is about getting lean, implementing explosive cardio like sprinting and battle ropes. In order for Johansson to build muscle, it was important that she consumed enough calories and protein, but Johnson says that he made sure that her diet was flexible. They still drank beers and had cake from time to time. Johnson says that it's important to still be able to enjoy life (even when on an intense exercise program).