This Is Exactly How Brie Larson Trained For Captain Marvel, According to Her Trainer

"For the first phase of training, I send every client to my colleague and good friend, who is a registered dietitian and MD, and they do blood work," Jason told POPSUGAR. The reasoning behind this is to find out if his clients have endocrine (hormonal) issues, which then allows him to figure out the best way to approach both training and nutrition. Once those tests have been completed, and he has a better idea of how each client's body is functioning, he'll then develop a nutrition plan.

Initially, Jason said Brie was in a calorie deficit to lower her body fat percentage. "It didn't take us too long to get her where we wanted her body composition," he explained. Once her body fat percentage was where they wanted it, he increased her daily caloric intake to fuel her workouts.

According to Jason, a lower body fat percentage helps with nutrient partitioning (where nutrients go when you eat them), "meaning the body is more efficient at dealing with carbohydrates." Jason didn't put Brie on a restrictive diet and said he encouraged her to eat a lot of carbs for energy.

If you scroll through Brie's Instagram, you'll see snippets of her training program like pushing a 5,000-pound truck, doing heavy barbell hip thrusts, and push-ups with chains. "So first off, everything you're seeing on Instagram, we want to make sure people understand those are highlights," Jason said. And before all of that could happen, Jason explained they established a three-month baseline of training before Brie began filming Avengers: Endgame. During that period, his goal was to teach Brie how to move and "to move well and connect with the body and gain a base level of strength," he said.

After they developed a foundation of strength, Jason said Brie trained twice a day for three weeks. Not only did she have to get stronger, she had to learn how to fight. According to Jason, "She did a lot of fight training and choreography." In order not to fatigue her too much, Jason and Brie would train about four times a week for approximately 90 minutes, she'd have a break to recover, then do fight training in the afternoons. After those three months, Brie was gone for filming. Jason described that phase of training as a maintenance program which allowed her to feel great on set.

Once filming wrapped for Avengers: End Game, Jason said Brie trained in the loading phase for three months in order to get her as strong as possible. If you haven't figured it out yet, building muscle and becoming stronger takes time.

"I was like, 'Wow, if I can get her as strong as I possibly can before she shoots [Captain Marvel], and she feels that, and she has the confidence going into it, that psychological reinforcement, imagine what it's going to do for her character,'" he said.

If you're ready to train exactly like Brie, check out the two-week program Jason created with Disney on the Playbook app.