ET spoke to Atwell at the 'Mission Impossible - Dead Reckoning: Part One' premiere in New York City Monday.
Entertainment Tonight hosted the U.S. premiere of Mission: Impossible - Dead Reckoning Part One at the Rose Theater at Jazz at Lincoln Center in New York City on Monday, and ET's Nischelle Turner spoke with Atwell about how Cruise saved her from adrenal fatigue.
"The virtual train carriage with Tom," Atwell said when asked about the most challenging stunt she did in the film. "So, it goes from horizontal to vertical in six seconds, so we'd have to sprint on an incline and reach the bar before we were dangling over a ravine."
She continued, "And that to me -- I mean I got adrenal fatigue at one point, and I just kind looked like a zombie, and Tom was like, 'Are you okay?' and I was like, 'I don't even know, Tom, what's going on with me. I don't know.' And he said, 'I know what you need. You need some chocolate,' and I was like, 'Yes I do.'"
Atwell said Cruise swiftly whipped out some chocolate and she was feeling good in no time -- so good in fact, that they were able to do the stunt a few more times.
As for how she trained for that physically exhausting stunt, Atwell said plenty of incline training.
"Richmond Park in London -- I can give you a tour of all the hills I ran, where I cried, where I peed behind a tree, where I wanted to take a nap, where I called my mom going, 'I don't think I can do this,'" the 41-year-old actress quipped. "It was that, but it was a lot of mobility training, injury prevention training -- so that you're doing it all really safely and competently, so I could make Grace physically dynamic as possible. So, by the time that I got on set, I could do anything that they ask me to do multiple times, and then add performance into it."
Cruise also offered some helpful advice following recent rumors that she and the 61-year-old have a secret romance.
"When I’ve talked to him about it, he’d be like, 'You know exactly who you are. You know what you’re about. And that is the only thing that matters. It doesn’t matter what people think of you, if you are in integrity with yourself, if you know what your value system is,'" she told The Independent over the weekend.
While Atwell called the rumors "uncomfortable," she explained that she views Cruise and Mission director Chris McQuarrie (a.k.a McQ) as "two uncles," noting that both Cruise McQ have encouraged her to play her role of Grace in the film as a strong female presence who has more of a sisterly relationship with Cruise's Ethan Hunt.
The Marvel actress also shared that Cruise and McQ like to "be surrounded by really strong, intelligent women," adding that the pair "love seeing women thrive and be in their own power, so if I ever tried to play small or flirtatious, or play damsel, they would probably be like, 'What are you doing? That’s not you!'"
While Cruise's relationship status is unknown, Atwell recently got engaged to boyfriend Ned Wolfgang Kelly.
See Atwell when Mission: Impossible — Dead Reckoning Part One hits theaters on Wednesday, July 12.