Game, set, match!
The film follows the legendary 1973 tennis match between Billie Jean King (Stone) and Bobby Riggs (Carell). The face-off became one of the most-watched televised sports events of all time, and was nicknamed the battle of the sexes.
“This was a really important and serious time in the women’s liberation movement, and it was one of the first times that a political issue was acted out in the circus-like atmosphere,” co-director Jonathon Dayton tells PEOPLE. “It just felt incredibly relevant to today’s time.”
To prepare for the role, both Carell and Stone spent months training on the tennis court.
“Steve practiced with Riggs’ trainer,” says co-director Valerie Faris. “He told us he’s never worked this long for a movie.”
And while Stone didn’t have a tennis background, she was more than happy to dive into the world of a famous athlete.
“Emma trained like an action hero,” says Dayton.
RELATED VIDEO: 23 Oscar Nominees Reveal The Untold Stories Behind Their Films
They say the actress gained 15 lbs. of muscle by hitting the gym and doing push-ups on-set.
“She felt so much responsibility to Billie Jean,” says Faris.
Battle of the Sexes bounces into theaters Sept. 22.