DWAYNE 'THE ROCK' JOHNSON says spending time with amputees in preparation for his starring role in 'Skyscraper' was ''one of the most unforgettable experiences'' of his career.

The 46-year-old action star plays the part of a former FBI Hostage Rescue Team leader and amputee in the new movie, and Dwayne has admitted that his preparation for the film was one of the most memorable experiences of his time in Hollywood.

Speaking to the South China Morning Post newspaper, Dwayne - who stars in the film alongside Neve Campbell - shared: ''It was an opportunity to play a character that was quite different from what I played in the past.

''I spent some time with amputees. It was very informative. It was one of the most unforgettable experiences.''

Meanwhile, Dwayne recently warned moviegoers that 'Skyscraper' will send heart rates soaring.

The wrestler-turned-actor explained that the film - which sees his on-screen character asses security for skyscrapers - is not for the faint-hearted, especially among people who don't like heights.

He said: ''There's been this Fitbit phenomenon which is very real, where people who are afraid of heights or have vertigo have been going to watch our movie wearing their Fitbits, and they have been reporting heart rates over 100 - sitting down.

''So this is a white-knuckler, it's a stomach tumbler, it's a pressure cooker not for the faint of heart. If you have vertigo, or if you're afraid of heights, it sounds like I'm joking about this but you will want to bring a friend.''