Thor: Love and Thunder hits theaters on July 8th, and ahead of its release behind-the-scenes secrets are coming out. While Chris Hemsworth’s arms are usually getting all the attention in the film, it’s Natalie Portman’s biceps that are the star this time around, and her trainer Naomi Pendergast has been revealing how she got her Thor-approved biceps.

Portman bulked up to play Jane Foster in the film, who was first introduced in 2011, “Thor,” ” and returned two years later for “Thor: The Dark World.” Pendergast told The Wall Street Journal, “Bulked-up arms were definitely the desired goal.” The Australian trainer said she spent ten months working out with the actor.

Pendergast talked to Us Weekly and said the workouts consisted of weightlifting, boxing, skipping around, and a lot of core work. The vegan also had to switch up her diet to get more protein so she could gain muscle instead of losing weight. “This amount of food was obviously way more than Natalie normally eats, but it was essential for her to maintain this throughout filming to keep the muscle she had developed,” Pendergast said.

As for if Portman and Hemsworth ever worked out together?” “Natalie and Chris did do some of their sessions at the same time but they did not work out together,” Pendergast explained. “There was a little bit of gym banter, but mostly everyone was focused on getting their workout done and done well.”

Portman is no stranger to shapeshifting. For her performance in Black Swan, which earned her an Academy Award, and Golden Globe, for Best Actress, she lost 20 pounds. “On ‘Black Swan,’ I was asked to get as small as possible,” Portman recently told the Los Angeles Times, “It was really awesome to turn 40 and feel the best I’ve ever felt physically. To be tasked for the first time with taking up as much space as possible, when most of the time as women we are asked to get as small as possible. Even things that had been aches and pains were cured by the strength training that evened me out and got me into balance in my body.”

It doesn’t seem like we are going to see Portman get any bulkier. “It feels good to be strong. I’m definitely not trying to bulk up [though], that’s not my personal lifestyle choice. Once you do the protein shakes, you’re not really eager to [maintain] that part of your life forever,” she told the outlet.

The news comes after Taika Waititi and Hemsworth revealed that some of the monsters in the film, are based on their kid’s drawings. After Waititi’s daughter grilled the director about what an oil monster is, she drew what she thought it looks like herself. “And then Taika said to me, ‘Tell your kids to do some drawings,’ and they did some drawings,” Hemsworth told People.