Rina Sawayama says she threw her back out during training for John Wick: Chapter 4.

The 32-year-old singer and actress discussed making her film debut in the action thriller movie during Wednesday's episode of The Tonight Show Starring Jimmy Fallon.

Sawayama plays Akira in John Wick: Chapter 4, which also stars Keanu Reeves, Donnie Yen, Bill Skarsgard, Laurence Fishburne and Ian McShane.

On The Tonight Show, Sawayama said filming as an actress was a "completely different experience" than performing as a singer. She then detailed the weeks of training she underwent for John Wick.

"So, we had, like, five weeks of training before the five weeks of shooting, which is all at nighttime, by the way. I mean, if you see any of the action scenes in the movies, they're usually shot 1 a.m. to 5 a.m.," the singer said.

"It was five weeks of training. Which is not enough," she added. "And then the first week, they were like, 'Oh, we're just going to do some drills just to get you warmed up.' I think it was honestly the first day of training, I did a move that we -- you just dodge underneath. ... So, I threw my back out."

Sawayama said she "didn't tell anyone" about her back out of embarrassment.

"But then, so I pinched a nerve. I don't know if anyone has pinched a nerve before, but it's terrible. It grabs the muscles around your nerve, and it shrinks it. So, I was trying to hide it. But after a couple of days, my spine started going like this," she said while leaning to the side. "So I was walking like this, and then I was like, 'No, no. It's absolutely fine. I'm not in pain.'"

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Sawayama concluded that the film was "the hardest thing I've ever done, but I would love to do more."

John Wick: Chapter 4 opens in theaters March 24.

Sawayama is known for the singles "Comme des Garcons (Like the Boys)," "Chosen Family," "Lucid," "Catch Me in the Air" and "Hold the Girl." She released her second studio album, Hold the Girl, in September.