Sylvester Stallone Does Pilates With Daughter Sophia For the First Time: 'It Ain't Cute'

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If Rocky can't handle Pilates, who can?

Joining his 20-year-old eldest daughter Sophia, actor Sylvester Stallone, known for kicking butt and taking names in the classic Rocky flicks, gave the trendy core exercise a try on Friday. The workout was so intense, he even compared it to taking on Rocky Balboa boxing rivals Clubber Lang and Captain Ivan Drago, but "before breakfast."

WATCH: Sylvester Stallone Reacts to Daughters Being Named Miss Golden Globe 2017: 'I'm Just Along for the Ride' 

"Brutal!" the 70-year-old actor captioned an Instagram testimonial featuring both him and his daughter post-Pilates. "This is an amazing workout but definitely not for the faint of heart. I've lifted weights, I have boxed, wrestled, track and field, played football and many other sports… But this workout pushes you to the limit… and beyond!"

In the clip, Stallone let his followers know what to expect if they decide to give the workout a shot.

"For anyone who's never tried Pilates – the name sounds cute, but it ain't cute," he warned, with Sophia in total agreement.

WATCH: Sophia and Sistine Stallone Walk Dolce & Gabbana Fashion Show -- See the Pics! 

Earlier this year, ET caught up with Sophia, as well as her sisters Sistine, 18, and Scarlet, 14, after being named Miss Golden Globe 2017 by the Hollywood Foreign Press Association -- the first time the title went to three people since the tradition started in 1963. Watch the video below for more.