Arnold Schwarzenegger made a unique return to his old stomping ground.

The 66 year-old recently visited Gold's Gym in Venice, Calif., to film an undercover camera stunt.

Sporting a black wig, fake moustache, baseball cap and a Gold's Gym uniform, Schwarzenegger played the role of 'Howard', pretending to be a gym assistant.

The hilarious video was to promote the After-School All-Stars mentorship and activities program for families who have a low income.

The 'Terminator' actor approached unsuspecting gym users and attempted to motivated them and provide fitness tips, which were questionable at best.

In the video clip Arnold explains what he is doing, "Basically, I'm going to play Howard, a physical fitness instructor who has become a regional manager for Gold's Gym," he said.

The member's reactions were of astonishment when they eventually recognised the former Governor of California, but even with his strong Austrian accent, some members could not see passed the disguise.

"Hi, how's it going? How many miles you running?" he asks a female member on a treadmill before she immediately recognize him and replies, "Oh my God. Hi!"

Schwarzenegger then shouts at one individual, "Stop being a baby. This is Gold's Gym, not a baby gym."

He also patted a man's forehead with a towel and said, "you look like your sweating a little bit, let me just take care of everything." The man did not notice the real identity of Howard at all.

The most hilarious moment came towards the end of the clip when Arnold looked at a huge photo of himself, on Gold's wall, from his bodybuilding days in the 1970s, and stops to say, "He looks so good. So handsome."

Gold's was the gym the 'Escape Plan' actor trained at when first moving to the US in the mid-70s at the age of 21.

Watch Arnold's undercover stunt below