If they make the movie, it will probably be called "Rambo, Part III -- First Sweat, Rockville."

Not much dialogue. Heavy on grunting. And, at regular intervals, meaningful grimaces.

So it was that Sylvester Stallone, bent on weekend weightlifting, paid a surprise visit Saturday afternoon to the Holiday Espre Center on Rockville Pike. He was accompanied by his bodyguard, his father and his fiance'. She was accompanied by a four-carat heart-shaped diamond.

"Thanks," he was heard to say when it was over.

"Oh, it's dirty," murmured Brigitte Nielsen when complimented on her ring.

Yesterday, local health enthusiasts were still debating the stature of the occasion.

"He's a comparatively small man," said WGMS radio personality Dennis Owens, who was jogging around the gym as the Stallone party arrived. "She was a tall blond babe. I'd say he was 5 foot 9 maximum."

"He's got great triceps!" said spa manager Susan Scott. "His biceps! The definition on these muscles is phenomenal! His lats! His deltoids were amazing! His abs were super too! I tell you, his hamstrings! His quads!"

"We've always been physical, sort of," said Rambo's father Frank Stallone, a longtime resident of Potomac. "He likes to work out every day. He's a workaholic. A physical person."

It was the elder Stallone, a member of the spa, who brought his son around, thus making good on a promise to spa regulars. Stallone the younger -- who is 39 "but looks 34," according to Scott -- worked his way from sit-ups to curls to upright rows in the free-weight room, and freely dispensed advice about body fat and nutrition.

"Nothing to tell really," his father said. "He just came to town unexpectedly and wanted to keep up on his training. Everybody was thrilled. We stayed there about an hour and a half. People came up and said, 'How did you get those muscles?' He was very gracious. Gave them advice. For him it's a religious thing, staying in shape.

"And diet. He doesn't believe in dairy products, milk or anything. He believes in protein and sometimes a little carbohydrates come into play. He believes that when your mind doesn't work too well, you need some carbohydrates to bring your mentality up. He sticks to whole-wheat bread. That's his mainstay -- sometimes two loaves a day. For meat, he's strictly a fish and poultry man. And vegetables and fruits."

The elder Stallone said Nielsen, a 23-year-old model from Denmark, is "under my son's tutelage." The bodyguard, he explained, was there "to avoid problems, you know, crackpots who want to be able to say, 'I punched Rambo in the mouth' -- not that he can't take care of himself.

"People misunderstand. Rambo is just a character. That's his work. His ambition is to play Edgar Allan Poe."