"I'm in pretty good shape," says the Hollywood veteran.

"I work out three days a week as opposed to six, which it used to be."

But he is nervous that he'll take too many real punches during filming.

"I keep thinking about it, because accidents do happen when you're in the ring with 250 lb. monsters.

"They tend to get carried away. They look across the ring and they tend to see Rocky - that's an occupational hazard."

Stallone has acted in the five Rocky films to date, the last being Rocky V in 1990, in which the boxer ends up penniless after his accountant loses it on the stock market.

The first Rocky film was released in 1976 and catapulted the star to fame.