The star - real name Dwayne Johnson - is in Yorkshire to shoot scenes for new Fast & Furious spin-off movie Hobbs & Shaw at the decommissioned Eggborough power station near Selby.The movie features stunts and high-speed car chases and also stars Idris Elba and Jason Statham.
Watch stunt helicopters film car chases at Eggborough power station during Hobbs & Shaw filmingThe Rock's team approached the owners of the World Fitness gym in Adwick, between Doncaster and Wakefield, on behalf of their client - but staff only found out about the former wrestler's visit half an hour before he showed up.
He spent 90 minutes training and chatting with other bodybuilders - including owner Craie Carrera, a Mr Universe competitor.
Craie's wife Alicia said:-
“We only knew half an hour beforehand that he was coming. When he walked in, people couldn’t believe it.
“A few weeks ago, we were visited by a bodyguard who said he had a famous client who was filming in the area and was interested in using the gym. He said he couldn’t say who it was and we didn’t ask. He took some photos and details of the gym and said he would get back to us when he had spoken to his client.
“When he turned up, he was great. He was chatting to members, posing for photos and signing autographs and everything. He was absolutely wonderful. One member got a shirt signed.
“He was really interested in Craie’s bodybuilding and was asking him about Mr Universe. He was giving him some tips and ideas for his training. He put him through his paces a bit!”