Nobody in this country has yet grown up wanting to be an Olympic rhythmic gymnast. Rhythmic gymnastics didn't become an Olympic sport until 1984, and even then it kind of took the rhythmic world by surprise.

Michele Berube, in fact, was an Olympian almost before she had a chance to think about it. "It was kind of a shock to me," she said, sitting on the floor of the Salt Palace Thursday, stretching out in preparation for tonight's first round of Olympic rhythmic gymnastics trials.The second round of rhythmic trials is Saturday night in the Salt Palace. The top two finishers from the eight-woman field, which was pared down from about 55 hopefuls at the national championships a few months ago - will go to Seoul, Korea, for the 1988 Olympics in September.

The men's and women's artistic gymnastics trials will be held Wednesday through Saturday, Aug. 6, in the Salt Palace.

Berube, one of the world's first rhythmic Olympians, has a chance to become a two-time Olympian. She was third at the national championships, which have a slight bearing on this weekend's meet.

At age 22, she is definitely a pioneer of the sport in this country, even if she didn't grow up aspiring to such things.

"We had no idea until the year before," says Berube about rhythmic's sudden entrance to the Olympics in the Los Angeles games.

When she did well at the '83 nationals, she was suddenly a favorite to be an Olympian. The world championships and international meets are just as important to the sport's insiders, she says. Nonetheless, the specter of the Olympics, with all its political overtones and glory, made it special.

"I was excited - but nervous," Berube says.

After the '84 Games, she retired to coaching, but now she's back competing again. She's in better shape than she was for '84, when she finished 14th overall. She's competed recently in the Soviet Union and France, and in the prestigious Four-Continents meet (everybody but the Europeans) she placed second all-around.

While Berube was retired, along with her '84 teammate Valerie Zimring (11th in '84 Olympics), Marina Kunyavsky was taking up the mantle of leadership. Now 23 and a college student, Kunyavsky won three straight national championships.

When she was 7, Kunyavsky recalls, her father asked her if she wanted to take regular gymnastics or rhythmic. "I really like to watch regular gymnastics," she says, "but I don't like to do it."

She chose rhythmic - probably one of the few little girls in this country to have gotten started in rhythmic right away. "You have to have the feeling of it," she says.

Kunyavsky's coach, Alla Svirsky of the Los Angeles Lights club that brings four of the eight competitors to tonight's field, says Kunyavsky, Berube, reigning national champion Diane Simpson of Evanston, Ill., and another of her pupils, Eugenia Yuan, are the four gymnasts to watch.

"Marina is very ambitious to make the Olympic team," Svirsky says. The coach paints a picture of a college student who's had to back off on gymnastics a little in the past two years and who's had bad luck in the last two big meets. Kunyavsky missed the world championships with an ankle sprain and did her very best in the '88 nationals, only to finish second.

"I did my best nationals this year," Kunyavsky says.

"She did a sensational job and had very high scores, 9.7 and 9.8," says Svirsky, "but the judges just preferred Diane."

Simpson earned a 9.9 on the second day of the nationals, Svirsky said, calling that an unheard-of score in this country an adding that it proves Kunyavsky didn't drop - that rhythmic performers are getting better in the U.S.

They have very different styles, these two national champions, Kunyavsky and Simpson. Simpson, long-legged and six inches taller than Kunyavsky, "is more modern . . . sharp movements," says Svirsky. "She is really tight," says Kunyavsky, who calls herself more balletic in style.

Simpson, now 19, started rhythmic gymnastics at age 13 after an athletic life of ice skating, soccer and artistic gymnastics. She did all that, played guitar and was an honor student.

When Irina Vdovets gave a rhythmic demonstration at Simpson's artistic gymnastics club, Simpson liked that, too, and did both kinds for six months.

Finally, something had to give. "I wasn't focusing on one thing but was trying to be the best in everything I did," she says. Her artistic coach told her to make a choice, and she chose rhythmic.

She calls all this stuff "quite an honor. Right now, I guess I classify myself as a world-class gymnast because I'm trying to make the Olympic team," she says.

Two of Simpson's teammates from Vdovet's Illinois Rhythmics club are also here - 17-year-old Dacon Lister and Berube. The other LA Lights are 18-year-old Irina Rubinshsteing and 17-year-old Alexandra Feldman. The other competitor is Laura David, 19, of Gymnos, USA, in San Rafael, Calif. She's coached by her mother, a former Olympian.

Most look at Simpson, Kunyavsky and Simpson as the leaders in a field of competitors that is very closely matched in talent. They all think they belong here; they all think they belong in Seoul.

"It's sport. You never know," says a philosophical Kunyavsky. She says she's never afraid of the outcome or the judging. "I do it for myself. That's it," she says.