Mark Wahlberg had a "gentleman underneath" him while he did pull-ups in 'Daddy's Home'.
The 44-year-old actor - who plays a bad boy dad competing with his kids' straight-laced stepfather (Will Ferrell) for their affections - had to shoot a scene where he does multiple one-armed exercises several times, but film bosses made it as easy as possible for him to make it seem "effortless".
He admitted to E! News: "I did probably about 700 that day. We did many takes from many angles.
"[There was a] "gentleman underneath" [me].
"They didn't want me to sound like I was giving an effort whatsoever so I'm talking very calmly during the push-ups and the pull-ups."
The movie also pays tribute to Mark's 'Boogie Nights' character Dirk Diggler by implying his alter ego is very well endowed - and the actor joked he is feeling the pressure.
He quipped: "I'm sick of being followed to the bathroom."
Mark previously revealed he risked a lot of money in casinos while researching his role as college lecturer and gambling addict Jim Bennett in 'The Gambler'.
He said: "I certainly did as much gambling as I could while preparing for the role and during the making of the movie.
"In Macau, I was playing pretty high-stakes blackjack.
"Like the character in the movie, I won a lot of money on blackjack and then I went right to the roulette wheel and lost it all."