How Emma Stone Gained 15 Pounds of Muscle for 'Battle of the Sexes'

Emma Stone as Billie Jean King in 'Battle of the Sexes'

Trainer Jason Walsh shares how he got the actress ready to play the legendary Billie Jean King.

Emma Stone stars as the legendary tennis champ Billie Jean King in Battle of the Sexes, which hit theaters on Sept. 22.

The biographical sports film, directed by husband and wife Jonathan Faris and Valerie Dayton (Little Miss Sunshine), is based on the 1973 match between trailblazing King and chauvinistic tennis player Bobby Riggs (played by Steve Carell).

To prepare for all the on-court action, the actress trained with Rise Nation founder Jason Walsh to bulk up. According to the film's costume designer Mary Zophres, "The first time I saw her for a fitting for Battle, her body had really changed, and it was really interesting.... Her body was such a different animal. She was such a delicate bird on La La Land, and she really muscled up for this role."

Here, Walsh, who counts Alison Brie and Emily Blunt as clients, chats with The Hollywood Reporter about getting Stone physically ready for playing tennis and helping her gain 15 pounds of muscle.


The truth featuring Emma Stone. Deadlift PR day. Change takes breaking comfort. #billiejeanking #movieprep #emmastone

A post shared by JASON WALSH (@risemovement) on

What was important in prepping Emma Stone for her role?

We went into it knowing that she was at least 15 pounds light. We were in the middle of doing La La Land and she was nowhere near looking and feeling like she needed to play Billie Jean King, one of the all-time great athletes. That's a big responsibility, so she really wanted to put the work in. I sat down and drew out the formula for what it was going to take. The aesthetic thing was kind of secondary. I knew she was going to be putting in a lot of hours, playing a sport that she's never played before. It's really inspiring to see a client like Emma who wants to go all in and really do the part justice.

What formula did you come up with for her?

She'd been working with me before, so we had worked a lot on her foundational movements. We really needed to tweak her diet, increase her calories, which we did through shakes. It's really hard to force someone to eat more, but the side effect of training like we did, [doing] really demanding exercises like heavy sled pushing and pulling, hip thrusting, squatting, lunging and deadlifting, it increases the metabolism. She innately had more hunger; she could not get enough food in. I knew that was going to be a response to the training, but we also wanted to make sure that she was getting enough calories without feeling disgusting or eating too much, so we put in a couple of shakes that we would do per day, because we were training twice a day on some days. We definitely trained five days a week. We really pushed her body way further than it had ever been pushed before. She became so strong, and her ability to become and look like a tennis star was there because we put in 15 pounds of muscle on. We did it safely and in a really organic, aggressive way.

Given that there are so many types of protein shake brands, was there a specific one you recommended to her?

We used this one that a lot of athletes use called Metabolic Drive, and it's one of the best-tasting shakes out there. We would put a handful of spinach in there and then we would put this stuff called Udo's Oil, because when we go on a lower carbohydrate [diet], the fats are really important for growth. Udo's Oil is a very clean product that I put in shakes myself, so we would put in 2 or 3 tablespoons of Udo's Oil for all of her omegas and fats.

What would a typical training session look like?

We would start out the day with pushing and pulling a heavy sled down a 25-yard track, and we would progress with more weights each week as she got stronger and her body started to adapt. Those were hundreds of pounds on that sled that she ended up doing, and it's very demanding but really beneficial for the body overall for strength.

We got up to over 300 pounds on her hip thrusts, and that's a weighted bar that goes over your hip as you thrust upwards. It really accentuates and utilizes the most important muscle group in the body to me — the glutes — because it stabilizes the hips and the spine and everything else just kind of falls into place. The focal point is getting the hips really strong. We'd also do really heavy and annoying single leg squats, where you have one leg back on a bench and it just isolates that hip and knee joint on one side. Her butt got really big for this. We did a lot of different types of circuit with the shoulders because tennis is a lot of shoulder, so we wanted to make sure she didn't get injured. She did a lot of pull-ups, push-ups, squats and heavy deadlifting. I think she got up to 185 pounds on her dead lifts.

This interview has been edited and condensed for clarity.