Joey King, 24, Says She 'Couldn't Hang' During Nicole Kidman's, 57, Intense Workout Routine

Joey King might be younger than her co-star Nicole Kidman, but apparently, it's not so easy keeping up with the 57-year-old actress.

24-year-old King—who plays Kidman's daughter in the new Netflix film, A Family Affair—recently shed light on the Oscar-winner's "intense" butt workout, which King admittedly said she "couldn't hang" for.

While making an appearance on The Tonight Show Starring Jimmy Fallon on Monday, July 8, the We Were The Lucky Ones actress recalled the fitness tips she received from Kidman, telling the late-night host, "She taught me the most epic, awful butt workout I've ever learned in my life."

"It was like, so intense," King continued, while she remembered thinking, "I'm a youngster, I can hang. I'm young, and I'm agile."

But that wasn't exactly how things went down.

"I thought I could hang, but I couldn't hang," King confessed. "It was these donkey kicks and rainbows and the fire hydrants and all these other [moves]. But you have to keep your leg in the air for like, 12 years. It's so hard."

But despite the difficulty level, King said she still sticks to the routine Kidman taught her, calling it "the most effective workout" she's done.

"I send [Kidman] photos when I do it," she further quipped. "I'm like, 'Call an ambulance, love you!'"

And Kidman wasn't the only co-star to give King some fitness pointers, as actor Zac Efron, who stars in the new film as King's boss, also helped the young actress learn about her protein intake.

"He's very helpful with the wellness tips," she said of the Iron Claw star, 36.

Talking about both Kidman and Efron, King gushed, saying, "They're both, like, so hot."

"They're so hot. They're the fittest people I've ever met. So I became a bit of a tubular gym rat on the set," she admitted.

A Family Affair is now available to stream on Netflix.

Next: Zac Efron and Joey King on Looking Up to Nicole Kidman