It's a sunny, warm Saturday morning about 7:30, as the would-be hard bodies straggle into Norwood Park in Bethesda.

Soon they are twisting themselves into shapes not known in nature, pulling and stretching and grunting on mats and towels on the asphalt path. Leading them in this ritual is Dave Slikker, 29, former Marine, recent Ironman competition contender and their exercise guru.

"Form, form, form, perfect form," he cajoles as the middle-aged folks work on doing push-ups. "Make it hard on yourself. . . . All the way down."

The four dozen men and women pay $65 a month each for the pleasure of having Slikker guide them to new levels of no-pain-no-gain exertion. The class is one of several run by the three-year-old Fitness Corps of Bethesda. Sole owner: Slikker.

With himself and his training skills as the main attraction, Slikker has found a tiny but successful niche in the country's multi-billion-dollar fitness industry. It's a business built on real sweat equity but little capital investment.

"I bought a couple of sets of weights. I bought a broom, so I could sweep out the patio of the other place we work out," Slikker said. "I didn't have to put in a big investment in it, except time."

Starting with 12 clients in the summer of 1996, the company now has 220 clients and five trainers in addition to Slikker. They conduct about 30 classes a week in Bethesda, Georgetown and downtown Washington.

Since it's an outdoor program, he mainly uses free space, such as Norwood Park and Freedom Plaza downtown. From the second week in December to the first week in March, he rents part of the Kenwood Country Club, but he gets "a real good deal" on rent in exchange for letting club members come to classes free.

The company's biggest expense is his five assistant instructors, who mainly have other full-time jobs and are paid by the class. His marketing has been largely by word of mouth, and he tries to make himself visible at local events and races.

The $65-a-month fee, after a $95 initiation fee, is designed to compete with the costs of other fitness programs in the area, similarly priced gyms and health clubs with more elaborate facilities but fancier prices. The fee entitles clients to attend as many classes as they want.

"I wanted to be competitive with the gyms," Slikker said. "I wanted a flat rate that would be affordable to all people."

The original military-style program in this area, the Sergeant's Program, charges $80 to $95 a month (depending on whether the client signs a contract for six months or a year). Slikker, who used to be a Sergeant's Program instructor before going out on his own, doesn't require contracts, letting people cancel with a 30-day notice. The better-known Sergeant's Program, which now is at 20 locations and has more than 800 clients, starts people out at "boot camp" and uses insults and humiliation as part of its notoriously harsh, drill-sergeant tactics. Slikker, a veteran of the Persian Gulf War, uses a milder approach, promising "no shame" and a "supportive, positive atmosphere."

Billing his program as "family fitness," Slikker has attracted mainly a middle-aged crowd. While he says he didn't try to lure people away from the boot-camp approach, the people who come to him are less likely to tolerate harassment.

One client who says the program has worked for her is Val Ford, 46, who works in advertising at Giant Food Inc. and was one of Slikker's original clients. She had him as an instructor at the Sergeant's Program and came over with him when he went out on his own.

"Dave's like a cult figure," Ford said. "He's this gruff ex-military guy with this soft side."

The business appears to be part of several trends in the large and growing fitness industry. According to the American Council on Exercise, personal training is "no longer for the rich and famous," and more people are exercising with a personal trainer in small groups. More people are turning to militaristic-style training, as well, the nonprofit organization said.

Slikker started with a partner whose marketing skills complemented his training expertise, but Slikker bought him out in November.

With its low overhead, the business started turning a profit soon after it began. "It wasn't very long [before it made a profit], and it wasn't very much," Slikker said. "I did it all without having to borrow money." He did have to dip into personal savings to live for the first six months. But Fitness Corps now makes enough to put 20 to 25 percent of what comes in into "savings," he said.

The Montgomery County native says Bethesda "has the perfect demographics for this type of business," with its large number of well-educated middle- to upper-income people. But the business is portable. "If I wanted to do this in Colorado or Alaska, I could do it."

At 19, Slikker decided college wasn't for him and went into the Marines. When he left, he continued to build on a passion for fitness and endurance sports, eventually finding both a personal and professional niche.

"It was a lifestyle," Slikker said. "And I turned it into a job."

CAPTION: Fitness Corps owner Dave Slikker checks the form of two of his trainees, above, during a morning workout at Norwood Park. Below, Slikker makes things a bit harder for Bill Hanlon, who is trying to finish an exercise with wife Betsy's help.