On the first day of the Men's Fashion Association Conference, David Warren of Arrow Shirts changed shirts eight times, and Elizabeth Wozniak of Aramis bathed four times in her company's muscle soak.

It's all because this is the weekend that menswear designers, manufactures and retailers meet the press with the best of their wares for the spring season. The conference of some 300 producers and journalists is put on twice a year by the MFA, the promotion arm of the $2.6 billion menswear industry.

New slimmer lapels, beefed-up shoulders, skinny ties and tapered trousers are the styles being talked about at the three-day marathon of shows, meetings and seminars which costs the MFA about $250,000.

Ten top New York male models have been imported for the event, including Michael Cathey, who modeled in Washington while working for the Hilton Hotel ehain. Like the others he says he has reduced his usual $100-an-hour, $750-a-day rate for this event, "because of the super exposure to buyers and press." He's also having a good time.

That is not surprising, considering the events put on by special groups. Yves Saint Laurent (minus the designer himself) is hosting a black tiedinner at a Moroccan restaurant, and the California Apparel Mart put on a noisy, splashy, choreographed show with 24 models.

At one point in the show, the models stripped off their business suits and paraded in brightly colored jockey shorts. In a sequence showing off skinny jeans, models appeared Elvis Presley-style in black T-shirts. Alongside the runway, a dozen swooning, screaming female models grabbed at the mock Presleys, one of whom took a girl's bra and shoved it down the front of his jeans as he walked off.

But the conference gets serious when it comes to proce tags. Hile the Consumer Price Index just released indicates an increase of 3.2 percent on apparel -- compared to an overall rise of over 9 percent -- high prices are still a major concern for everyone here.

Between 1967 and 1978, men's suit prices climbed 44 percent, and men's shirt prices 50 percent.

Norman Karr, executive director of the MFA, credits competition in the business -- made up mainly of small companies and a few giants -- for the relative price restraint. With close to 400 different companies and contractors making nothing but men's suits in this country, says Karr, the competition can cause "a markdown mentality."

"There's a tendency to anticipate that the guy down the street is going to mark down something," Karr says. "And if he does -- and you don't -- you could get stuck with a lot of merchandise."

Many aspects of the industry are being debated -- among them, the fear that the all-cotton shirt may become an endangered species. Peter Kamins of J. P. Stevens and Oc. is worried about government action to reduce the hazards of cotton dust. "I'm just not sure that American mills will have the capital or the technology to meet the new rules," Kamins said. "There requirements are becoming so overbearing it's possible that the consumer will have to accept less cotton."

James Veeder, a form,er Woodies buyer who is now vice president of menswear for Catalina, foresees increased business in Europe -- a positive result of the declining dollar overseas -- and an overall interest in American sportswear and in the '50s' look sparked by the movies "Grease" and "Saturday Night Fever."

Manufactures are not counting on any real competition as a result of new China trade. Norton Binder of Robert Bruce, a firm thatonce imported jeans from China, said, "They can produce a lot of goods cheaply because they control labor and have endless raw materials but their marketing knowledge is not at all sophisticated." He thinks it will be a while before China becomes an important competitive force in the menswear market.