Alicia Vikander has transformed herself into Lara Croft completely, gaining 12 pounds of muscle to play the character for the upcoming film Tomb Raider.

The Oscar-winning actress worked with trainer Magnus Lygdback three months before production began for the big screen adaptation of the video game.

Body Transformation

Despite being a trained ballet dancer for years, Vikander, 29, says that Lara Croft is her first role that required her to do such rigorous training.

"On this job, it was the first time I was expected to do as much muscle and weight training as I've done," she says in an interview with ET. "I've really felt it very empowering, and I still feel like I have a physique."

The actress has always been slender, but she and Lygdback wanted to make her more toned and pack more muscles into her 5'5" frame. While there wasn't an exact weight goal, the pair wanted to build more muscle to create a character that moved and looked a specific way.

Not only did Vikander sport ultra-toned arms and back, but her abs went far beyond the usual six-pack.

"You don't see that too much in the movie, but she's got an eight-pack," Lygdback says. "I'm really proud about her core."

"I already wanted her to be a strong, physical girl," Vikander explains. "This film is about her becoming the action hero we know her to be."

The Workout

Lygdback reveals that his training program for Vikander required a lot of hard work and dedication — two things the award-winning actress has in spades. However, he also stresses that quality of workouts is more important than the quantity of hours in the gym.

In a report from USA Today, Lygdback shares more of his training methods with Vikander, which included a lot of strength training, even more food, and minimal cardio exercises.

Intensive mixed martial arts training was a big part of Vikander's preparation as well as rock climbing and swimming.

As her workouts increased, so did Vikander's meals. At one point, she was eating five times a day, most of which were quite protein-heavy.

The combination of workouts and diet helped her develop a strong core and eight-pack abs, which was important in the numerous fight scenes and physical stunts of Tomb Raider, such as getting tossed around a raft and swimming in freezing water.

Tomb Raider is slated to hit theaters on March 16.