Jennifer Garner Reveals How She Got In Fighting Shape for ‘Peppermint’ (Exclusive)

The former 'Alias' star opened up to ET about how she got ready to rack up a serious body count in her gritty revenge thriller.

In Jennifer Garner's upcoming action revenge thriller Peppermint, the actress racks up a massive body count as she fights her way through a drug cartel in a search for bloody justice.

The film is a far cry from the grounded dramas and family comedies she's frequented in recent years, and the grueling role called for the actress to get back into combat-ready shape.

"There was a lot of training, it was very physical," Garner recently told ET's Kevin Frazier while she was promoting her upcoming film. "I was in pretty good shape going into it, and I said to them, 'You know, I know how to train for this movie, I can get where I need to go and I know what I need to do,' and they said, 'OK.'"

So Garner turned to a personal trainer, who had her take on a plethora of unique exercise techniques.

"We did a lot of dance, cardio, but we also you know did crazy weights and I did bands,  and did trampoline, and did everything," Garner recalled. "I also boxed every day, and then I trained with the stunt team."

Garner said that, when she was filming, she almost unconsciously found herself channeling her iconic Sydney Bristow role from her years on the ABC action series Alias.

"At first, when we started shooting, I would be back in action mode I would just kind of fall into being Sydney Bristow," Garner said. "I walked liked her because my body had this memory of it. But Sydney was an optimistic young girl who was out to take care of things, but she had an optimism to her. Whereas my character Riley North [in Peppermint] everything has been taken from, and she is at the depths of the depths and is coming at it from an almost animalistic point."

In Peppermint, Garner plays a woman whose husband and daughter are murdered in a drive-by. When she awakens from her coma, she dedicates her life to learning how to fight and kill, then seeks out those who took everything from her.

"There was a time I did something where I walked up the stairs and… I looked back over, and [when] I got up the stairs, I was like, 'Hang on, let me do that again, that was pure Sydney.'" Garner shared.

ET previously caught up with Garner at CinemaCon in Las Vegas back in April, where she said it "felt great" to be a part of a movie that included a stunt team again.

"My stunt double and I have worked together since I think the third or fourth episode of Alias… So she's like my sister," Garner said of her reunion with friend and stunt double Shauna Duggins. "So [it's been great] for the two of us to get to be together every day, to train together, to go back to all of that."

Fans can see just how action-packed and dark Garner's revenge journey gets when Peppermint hits theaters Sep. 7.