LONG BEACH, Calif. (AP) -- SYLVESTER STALLONE, the star and driving force behind a new movie revolving around the CART series, said his introduction to open-wheel race cars was not what he expected.

``I wasn't aware that you basically lie down in the car, so it was very odd realizing that you go into the great unknown basically feet first and that was kind of unnerving,'' said the man who starred in the ``Rambo'' and ``Rocky'' movies.

``Second, there was a rattling all the time I was driving the car, so I thought, 'This car's coming apart,' until I realized it was my knees. So there's a fear factor that permeates one, and I realized it takes quite a while to get your heart, your body, your adrenal glands to settle down.''

STALLONE, who did a lot of his own driving in ``Driven,'' which will premier in Los Angeles on April 16 and go into wide release April 27, said he spun out numerous times during his preparation at a Las Vegas driving school.

``It finally dawned on me about drift and precision and powering into an apex and speeding coming out so it's just getting the actual flow,'' he said. ``It's almost like music and you start getting into a hypnotic rhythm. Then you start to push a little bit more and push a little bit more, and I was captivated by that.''

The actor, who appears to be very physically fit, was also surprised by the G Forces a driver is subject to.

``The next day, I was totally aware of it when I had to have someone brush my teeth for me,'' he said. ``I couldn't move my hand, I couldn't form a fist, my neck, forget it, you could use my head for a lamp, I couldn't move.''

He came away from the project with great admiration for professional race drivers.

``I try to explain to people that driving a race car is like speeding across an ice field.'' STALLONE said. ``The car is almost floating and that's the skill of driving, maintaining this car while its barely having adhesion ... to the track. It just puts you right to that ragged edge. That's an extraordinary skill to maintain that balance and coordination.''