Spectacular Olympic gymnasts pushing out barriers of the sport.

The sky, modern gymnasts keep telling us with their performances, is not the limit. Like jet flyers, they keep pushing back the ''envelope,'' going beyond what anyone thought possible only a decade or so earlier.

There's a problem, though, and it has become increasingly apparent ever since Romania's Nadia Comaneci scored the first perfect 10 in the Olympics at Montreal eight years ago.

The judges have run out of numbers. And as a result, 10s seem to be getting a lot more exercise than they should.

A case in point occurred during the opening round of men's Olympic compulsory exercises here in Los Angeles. With the competition barely two hours old, the skilled Chinese team had scored six 10s, already equaling the total of six for men at the 1980 Moscow Games, where they first broke the Olympic flawless barrier.

Even if perfect scores don't exactly grow on trees, they appear within the reach of many more gymnasts than ever.

After two days of Olympic competition at UCLA's Pauley Pavilion, eight athletes had hit the jackpot, including Americans Mitch Gaylord and Peter Vidmar.

''A 9.9 is a certificate of participation. A 10 is what it takes to win,'' said Gaylord, who nailed his parallel bars routine.

Teammate Bart Conner echoed this when he observed, ''There will probably be some people in the Olympics who will score 10s along the way and may not win a medal. I know that's hard to believe, but it could happen.''

''Yeah, how could a person ever explain that to his mother,'' asks US women's Coach Don Peters half jokingly.

Peters feels that judges sometimes back themselves into a corner, awarding 10 s when they may not be merited.

''Seldom is there a routine that's perfect,'' he says. ''Often an athlete gets a 10 because one who performed earlier got a 9.9. The problem comes in when there's someone even better waiting to go.''

The compulsory marks here were not so spectacular for the women, with Romania's Ecaterina Szabo turning in the lone 10. But that may all change with today's women's optionals, which complete the team competitions.

These personalized routines make up 50 percent of a gymnast's overall score. They give the women a chance to play to the crowd and rack up points in the process, both with spectators and judges.

Theoretically, the judges are unaffected by the audience's reaction, but in practice it doesn't always work that way, and everyone knows it. In Montreal, for example, even the judges quite likely got caught up in the Nadia craze to some degree, giving her seven perfect scores.

Asked his reaction to this run of 10s, the Soviet Union's Nikolai Andrianov, the winner of 15 medals, once replied, ''Ask the judges. Women are always more interesting than men.''

If that's true, it's probably because the women amaze people with the energy and grace they package in such small bodies. The top two American females, for instance, are 4 ft. 9 in., 92 lb. Mary Lou Retton and 4 ft. 10 1/2 in., 88 lb. Julianne McNamara. The men, by contrast, are generally expected to be more powerful with their inverted-V physiques.

Even so, the men seem to be earning as many 10s as the women these days. The whole situation has served to dilute the significance of the sport's loftiest goal.

Officials of the International Federation of Gymnastics expressed concern about the proliferation of perfect scores at last year's world championships.

Ways of avoiding this situation are under discussion at meetings here. Among these is the establishment of standards of difficulty, such as is done in diving , so that only the most difficult routines could earn 10s.

Another possibility would be to remove the ceiling from the scoring procedure. ''I don't know why it has to stop at 10,'' says Peters. ''Why does it have to be locked in at the top? The standards the judges use were out of date before they were even distributed.''

The race by gymnasts to come up with new and exciting moves has made it difficult for even insiders to know the technical nuances of each trick.

Further complicating matters is the speed at which a succession of moves is executed. They come rat-a-tat-tat in an event such as the floor exercise, happening almost faster than the naked eye can see.

The slow-motion TV cameras ABC has trained on the Olympic competitors this week would be an invaluable aid to the four judges who work each event.

With this equipment, every slight loss of balance and bending of the leg could be detected. Perfect scores might virtually disappear, too, which doesn't seem like such a terrible prospect really.