It's no pain, no gain for Ali Larter.
ET's Deidre Behar sat down with the 40-year-old actress at the junket for her new film, Resident Evil: The Final Chapter, at the London West Hollywood on Saturday, where she opened up about how she got in shape for the action flick, just months after welcoming daughter Vivienne.
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"I think the difference is that I work out when I don't want to," Larter admitted. "I push myself."
"I work out like five days a week, and I don't usually want to those extra couple of days," she said. "I'm someone who likes to sweat. I love to do hot yoga. I enjoy running, but I'm not someone who can just go to the gym."
"I cook a lot and I eat, so I'm not someone who deprives herself," she continued. "But it's also from my work. When I started this movie, Vivienne was six months old. I had gained 50 pounds [during pregnancy], and I was like, 'Oh my gosh, you need to get to work, girl!'"
"This is a post-apocalyptic world. You can't be doughy, you know? You need to be lean!" she joked. "This movie is physical, it's an action movie, and you have to be believable in a post-apocalyptic world."
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Speaking of Larter's little ones, the actress, who shares now-nearly 2-year-old daughter Vivienne and 6-year-old son Theodore with husband Hayes MacArthur, also shared the advice she'd give her kids if they ever wanted to follow in her acting footsteps.
"I would say that when you're 18, you can go to college and you can learn about it," she confessed. "You can study acting, and then you can start at the very bottom as a PA on set, and you can work yourself all the way through every department so you really revere the work that everyone does."
"I think that one of the shortcomings of being an actress, at least in the beginning of my career, was thinking that I was just a for-hire, and that I had to wait for a project to come," she explained. "If my children were in this, I would make sure that they knew how to create the material themselves."
"[But] I don't think they will be [following in my footsteps]," she added. "I don't see it in my kids."
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Resident Evil: Final Chapter hits theaters Jan. 27.
See more on how Larter manages to juggle it all in the video below.