Exit breastplates. Enter the belly belt.

There are moments of the usual fun and games during the annual rites of spring in Paris this week where designers are presenting their ideas of what to wear for the next warm season. But with the current concern about the economy and high unemployment and uncertainty about the upcoming elections in the United States and France (next April), the currrent collections in Paris downplay some of the extravagance of past seasons.

French designers, nervous about future business, particularly with cost increases of as much as 15 to 20 percent, are sticking to familiar shapes and colors, reluctant to go to any extreme that might be rejected. Even Karl Lagerfeld, who prides himself on forcing new ways of making clothes each season, and Claude Montana, who designs costumes fit for grand opera, have created clothes which leave no buyer any reason to be nervous.

"There's hardly one thing in the Claude Montana show that I couldn't wear right off the runway," said Hanne Merriman, Garfinckel's vice-president. The Queen of the Nile dresses were the obvious exception. And there were others, too, to replace last season's ultimate fantasy -- breast plates a la Wonder Woman. This year's silliness includes belly belts a la your favorite joke store (but in Paris molded in gold and shown by designer Thierry Mugler), inflated black vinyl riding jodhpurs with matching bra at Issey Miyake, breast art (painted nipples) and gold paperbag pants by Jean Paul Gaultier.

The fashion pack is viewing these creations after spending last week in Milan looking at the Italian offerings for spring '81, and some will move on to London when the Paris shows have ended. The grand tour concludes, for Americans at least, on Seventh Avenue at the end of this month.

Actually there are fewer buyers and press than usual in Paris at these showings, which are curbed by the high cost of survival in Paris as well as the lack of rip-roaring success of the fashion business this season, except at the very top price level. But the groupies, who follow the designers like David Bowie or John Travolta followers, swell the crowd to at least double each hall's capacity. Some designers, including Mugler, Kansai and Montana, supposedly send out as many as 4,000 invitations to make sure their antics are appreciated. Plus there are all the fake invites, the invites passed from someone inside to a pal outside, and those who slip with the uncontrollable crush.

Even the ways the models present the clothes these days seems more, well, reserved this time round. There are fewer American models -- Jerry Hall, Mick Jagger's girlfriend, is an exception, and very few black models. And to rouse the audience, a couple of times models have stuck the flowers from their hair into their mouths just to try to get some kind of reaction. No one seemed to notice much.

This more serious attitude also shows up in the party scene, or lack of it, in Paris this week. No costume balls, no extravagant dinners. "People are getting scared of big parties," insists Lagerfeld, who has hosted some of the most lavish affairs in Paris. "It has gotten so it is sometimes dangerous and you feel harassed," he says. Lagerfeld adds that he sometimes feels so threatened that rather than walk to the taxi stand at his corner, he has hired a chauffeur.

So to soothe and pamper the crowd that has traveled to Paris, the organizers have grouped the shows together in four Quonset huts built for the occasion next to the Porte de Versailles, the huge exhibition hall where hundreds of other French manufacturers set up stalls and show their clothes at this time to shopkeepers. Buses were organized to meet buyers and press arriving by Metro. That was a good idea except that by Sunday, one of the busiest days, additional bus drivers got their directions mixed and never got farther than the parking lot, leaving buyers and press stranded for transportation.

And the restaurant built to accommodate those at the ready-to-wear shows serves only a cold buffet at 99 francs ($25).

Only Emanuel Ungaro, who showed his much applauded collection in an 18th -century mansion he rented from Pierre Cardin, and Kenzo Takada, who will present his collection in a tent put up in Place Victoire in front of his boutique, passed up the chance to show their clothes in the new setup, which was offered free to designers.

Lagerfeld, who was leery of the non-central location and lack of charm in the "tents," as he called them, admitted after his rehearsal, though, that the place was quite professional. "And besides, it is always good to show your things in a new place. To return to an old place is like going back to a family grave."

Designer Pierre Cardin climbed over photographers nearly three deep to get to his seat at the Montana show, "This is no longer for the people in the street. This is couture," said Cardin. He's right. Costumes that now cost over $250 for a blouse alone and $1,000 for a suit by the time they hit Washington stores, are really in the couture price range.

But if the designers aren't sellin these clothes to the people in the street, as Cardin calls them, they are shameless about stealing the ideas from what young people are in fact wearing today in Paris. From the kids in their olive drab surplus clothes and men and women in loden green sweaters, pants, jackets, coats and even cars, the olive or loden color is so apparent it is likely to bounce shades of purple as the favorite color in Washington, and elsewhere, these days. And from the popularity of American Indian things -- from fringed leather jackets to beaded moccasins and turquoise jewelry -- the designers have created everything from headbands and fringe and Indian designs as well as turquoise and silver accessories.

The new shape of pants to succeed the skinny cigarette leg and then the baggy is the jodhpur -- which most fashionable women wear in suede or corduroy, and only a few in authentic gabardine. The jodhpur appears in most every show both in soft fabrics and stiff ones, for daytime and evening.

And the blouson, which here in Paris is more standard than the blazer, is a popular jacket in most collections -- but also shows up as blouson (loosely bloused) tops of dresses as well.

If there is one street fashion missed so far by designers it is the table-cloth-check cotton Palestinian scarf in red and white or black and white, worn by young Palestinians and their sympathizers. If the designers missed that message it hadn't been overlooked by some of the audience. At least one British editor and one French photographer had them wrapped around the neck.