Washington lawyer Morton H. Wilner does not pump iron at his downtown fitness club. It's step-ups and neck-flexes only, then a soak in a steaming whirlpool for the 74-year-old attorney who starred on the University of Pennsylvania's football and baseball teams in the 1930s.

"I'm an old, broken-down athlete," said Wilner, chuckling after a workout last week at the Office Health Center, one block from his law firm. "I do this to keep the arthritis away."

Wilner is one of thousands of Washington exercise enthusiasts who keep more than 20 fitness centers in the city filled from early morning to well into the cocktail hour.

Although high-pressure sales and uneven service records have tarnished the reputations of some exercise clubs in the District, industry spokesmen say business at Washington spas is healthier than ever.

Unlike the mushrooming suburban health clubs, downtown fitness centers must rely on the daytime crowd only -- the commuter out for a lunch-time workout. Still, those in Washington are doing unusually well, according to representatives of several clubs. Six hundred people use Washington's lone Holiday Spa each day, and the company plans to build three more in the city. A Nautilus center on Pennsylvania Avenue has 1,500 members -- about 500 more clients than any one of the suburban Nautilus clubs. And the Office Health Center has three times the number of clients it did eight years ago.

"This is a well-educated city, and because of that, the people here are more aware of, and have a slightly better attitude about their health," said David Frenzel, who opened the Office Health Center 10 years ago at 20th and M streets NW. "The demand for health and fitness centers here is one of the best in the country. You can tell, the people here look better. Doctor friends of mine tell me there is very little obesity here.

"And they're right: You don't see many fat people on D.C. streets," Frenzel said.

Frank Bond, Holiday Spas' board chairman, agreed. "Downtowns can't compete with the suburbs, but a place like Washington holds its own. The people are much more sophisticated than the average guy." Washington's fitness clinics range from no-frills workout rooms, where a yearly membership may cost less than $300, to posh squash courts for those who can afford a $1,000 annual fee. In between lie the majority of clubs: clean, well-managed facilities where $350 to $500 buys a year of weight lifting, jogging, saunas, whirlpool baths and towel service.

In this business, however, consumers do not always get their money's worth. Two years ago, for instance, 52 disgruntled customers sued the management of the Holiday Spa, at Connecticut Avenue and L Street NW, after the facility closed when the building it was in was demolished. Under a consent decree, the firm agreed to pay refunds of up to $200 to each customer in the suit and smaller amounts to another 200 people. Customers were also given extensions on memberships they had paid for and allowed to use the Holiday Spa that opened on K Street later that year.

Officials at the Federal Trade Commission also report they are investigating some of the business practices used by local fitness clubs. The officials declined to identify clubs under investigation.

"Since the Holiday Spa case, the industry on the whole seems to have been behaving itself," said Mike Blair, a lawyer in the D.C. Office of Consumer Protection. "Most of them have been very responsible, in part because we have such a strong law to regulate them." The 1976 D.C. Health Spa Consumer Act, one of the toughest in the country, gives spa customers a 15-day grace period to cancel their membership contracts for any reason. If the consumer backs out, the spa may keep a small portion of the initial fee.

Blair and a spokesman for the Better Business Bureau here said they get a constant stream of questions and complaints about downtown health clubs. "We get an average of three or four inquiries a week," said Marsha Goldberg, a trade practice consultant with the Better Business Bureau. Goldberg, who is writing a study of D.C. area fitness centers to be published next month, said customers are often annoyed by long waits for equipment, dirty locker rooms and showers, and by inflated claims about operating hours and services.

"You can have a really good experience, but if you don't take care in picking a club, you end up throwing your money away," Goldberg said. She and Larry Hodapp, a Federal Trade Commission lawyer here, urge customers to shop around for the program that suits them best.

"Before somebody signs a lifetime or long-term contract at a health club, they should go to the spa at the same time of day when they expect to use it. That way, you'll see how big the crowd is when you want to use it," said Hodapp. "Some of these companies have very high-pressure salesmen. People need to take the time to reflect on what they want" and be sure not to purchase more than they need or can afford, he said.

Last week the Holiday Spa at 17th and K streets NW was filled with lunch-time joggers running around a mirrored salon and muscular men and women pumping iron, including a professional bodybuilder lifting over 750 pounds by leg-power alone.

Betty Reedy, a researcher for the World Bank, had nothing but praise for Holiday Spa, even though it lacks the sauna that most other clubs have. "I really like it here a lot," said Reedy, taking a breather from leg exercises. "I'm already pretty thin; I come here a lot just to firm up." She said she pays about $25 monthly for her Holiday membership, a two-year package that costs just under $600.

Manager Shelia Cook said Holiday wants to open another, larger spa downtown. "The negative publicity of the lawsuit in 1980 never hurt us. It was weird, but after we opened here the same year , people called us up out of curiosity to find out about us. Maybe it takes bad publicity to generate good publicity."

Cook, who has been in the fitness business for the past 10 years, said, "Outside of maybe Los Angeles, the people in D.C. are more fitness-crazed than anyone else in the country. This is a terrific town for us."

Men and women share the workout area at both Holiday and the Nautilus fitness center at Pennsylvania Avenue and 19th Street, where business was booming one morning last week. The aerobic exercise room was vacant, but the weight-lifting room was packed. The entire bank of Lifecycles, futuristic gizmos with glowing consoles that simulate uphill pedaling, was occupied. The thunk-thunk of disco music complemented the banging of 50-pound weights. A sign on the whirlpool bath said it was temporarily out of order.

"We have a real social atmosphere here," said Susie Kushner, a Nautilus manager. "It's a real club feeling. Our customers all get to know each other, and some people stay here for three hours" to socialize. Customers often have to wait to use the equipment, but such delays are usually short, she said. Membership at Nautilus, which like its competitors frequently offers price reductions, can cost as much as $500 per year. The center, which opened two years ago, features 13 different weight machines, including one for "negative parallel dips," an exercise that resembles some form of medieval torture.

Yet, the demand for a club that concentrates almost exclusively on weight-lifting remains high; Nautilus owners plan to open a new 7,200-square foot club this winter at Vermont and L streets NW.

The atmosphere at the Office Health Center, which has separate facilities for men and women, was more tranquil at noon than in the other clubs. Fine art prints and muted Bach massaged the eyes and ears of patrons, who could relax in a camphor-scented steam room after working out with the standard exercise equipment.

"We don't even consider ourselves to be related to most of the industry," said Frenzel, a management consultant who opened his own center. His club has a low-key atmosphere; Frenzel relies solely on word-of-mouth and company exercise plans to bring in new members. Annual membership in the Office Health Center costs $348.

Although they differ in style, the clubs draw a wide range of customers--including lawyers and bankers, students, office workers and waiters.

Determined to survive in a business with more than its share of failures, the managers of most Washington clubs are attempting to overcome the past blemishes on their industry. And thanks to the District's health spa regulation, "we may have chopped into that old saying, 'Caveat emptor' " said Blair, of the city's Office of Consumer Protection. "But the buyer should still beware. Think before signing that contract." CAPTION: Picture 1, The Nautilus health center at 19th and Pennsylvania offers disco music to work out by. By BILL SNEAD -- The Washington Post; Picture 2, a bike at the Office Health Center with employe Ralph Hendry. Photos by BILL SNEAD -- The Washington Post; Picture 3, Paulie Sturtevant on Lifecycle machine at Nautilus. Photos by BILL SNEAD -- The Washington Post; Picture 4, Betty Reedy, a researcher at the World Bank, takes part in the weight training program at a Holiday Spa for $25 a month.