Emma Stone was a true champion when she bulked up to play legendary tennis player Billie Jean King in upcoming biopic Battle of the Sexes.
The 28-year-old Oscar-winning actress put on 15lbs of lean muscle as she transformed her body into that of an athlete's, and was "ecstatic" when she started putting on weight, according to her trainer Jason Walsh.
"She was ecstatic when she got on [the scale]," Walsh told People during a joint interview with Stone.
"Most girls who get on the scale and gain weight freak out, [but] she had the biggest smile in the world when the weight started to increase."
Before Stone's intensive training, Walsh described her physique as "pretty light" and "very petite, dancer-type".
"I wanted to put some weight on her, some muscle on her," Walsh continued. "We really shifted the diet plan. She started taking in more good, healthy calories," he continued. "The intensity of workouts shifted as well.
"We started doing training geared toward getting more weight and muscle on her, so it was a little more believable onscreen, and also for her mind and her character."
The La La Land star added that she committed to "about three months" of weight training for the part, with Walsh saying she went from working out three times a week to five, and sometimes trained twice a day.
"She got really strong, I'm talking like, we were pushing and dragging sleds with hundreds of pounds, which was awesome to watch," he recalled. "It really became fun for her. [She] would be like, hey, what kind of record are we going to beat this week with the weights?"
Stone stars opposite Steve Carrell in the film which chronicles the iconic 1973 tennis match between King, ranked at World Number 1, and Bobby Riggs, a retired Grand Slam Wimbledon champion, for a $100,000 prize. The challenge became one of the most-watched televised sporting events of all time.