"All right, everybody on their feet," shouts James Alexander. "Legs apart for sweeping the floor. Let's stretch and pull those muscles out."

Fifty men and women stand at arms' length on the deck of the Capitol East Natatorium. Everbody sweats as they swing their arms to the rhythm of Alexander's one, two, three. Only a few are moving effortlessly; the huffers and puffers are concentrating, hard.

They're all in Swim and Trim, a program for "creatively active" people.There are no initiation fees; only Alexander's regulation that you attend the exercise sessions before going on any of the fields trips.

Ask them why they're here and you get words like fulfilling, meaningful. Watch them coming every Wednesday and Sunday to stretch, bend, touch, lift and twist their bodies; you'll hear them complain that 'Alexander is trying to kill us."

"Alexander is a pusher. He really gets you out there. But it's at your pace; what you can do. He never forces you," says Arnold Jefferson. "Some people say they can't do this. They can't do that. And most of them, once they really try, find they can do almost everything."

"That's right," agrees Alexander; a small, middle-aged man with an extra-large mouth. Although he'll humor you, Alexander is not the most tactful person you'll ever meet. He's not threatening, just straight to the point. Once he told women in the group, "Seventy-five hip rolls a day and less trips to the refrigerator will take care of your over-budding behind." His easy-going partner, Glen Shackelford, balances their act with gentle wit and charm.

At Swim and Trim there's no fancy gym equipment, just the two dedicated and supportive instructors who volunteer their time. You can spend an hour working up a nice sweat, then swim for another hour. The Alexander and Shackelford principle is you don't have to push yourself. You can do as much as you can handle.

Frank and Pat Murphy came because "Pat was overweight."

"That's not nice," she says."It was because of the bus coming at me. I tried to run. I couldn't. My whole body was stiff and underworked."

"She and my daughter were going to sign up for a $500 course," says Frank. "Then my daughter heard about this volunteer group working down here at Capitol East. We love it. Of course, we saved all that money, but it's mainly the people, the marvelous people."

Alexander arrived in Washington after he toured with the Harlem Globetrotters. He loves dogs and children (not necessarily in that order) and saw how they use the parks; he thought adults should have organized recreation periods, too. So he and Shackelford got interested people together and formed Swim and Trim.

The field activities offer something for everybody, including marching in parades, canoe and white-water raft trips; overnight and day hikes to scenic locations. The hike in the Shenandoah is an all-day trip. When you get back you're really worn out, but you've had a beautiful day with 40 to 50 people. Alexander borrows a recreation bus, everybody brings their own lunch and chips in for gas. It's like being a kid again on you way to camp.

"The most important thing," says Carleen Draper, a new member who has just discovered the joys of hiking, "is that you know your own limitations. If you hike five miles down into a steep canyon, you better be able to hike out again."

"I like the hikes," says Gloria Smith. "In fact, I can walk all day. But I like the bike rides best.I learned how to ride a 10-speed, how to shift gears, how to go up and down hills and get better balance. I even ride on my own now without fear of riding in the streets or getting a flat tire and not being able to get back home."

Swim and Trim bikers ride to Fletcher's Boat House, Seneca, Rock Creek Park, Mount Vernon, Great Falls and, once a year, do an overnight 80-miler along the C&O Canal.

"We have someone in the front and rear to make sure everybody stays together," says Alexander, adding: "If something goes wrong like a flat tire or a seat comes off, we all stop for an on-the-spot how-to-repair lesson."

Not everybody in the program shares Gloria's enthusiasm for biking, but most of them will run. Swim and Trim runners and joggers meet every Saturday for a few fast spins around the National Arboretum's rolling hills. A few Swim and Trimmers have gained enough confidence to run in competition. Alexander teaches them that their emphasis should not be so much on winning as on the stamina it takes to finish, possibly with a good time.

He says, "Just the fact that they can do it really does a lot for their egos."

That's how another Swim and Trimmer feels about swimming.

Al Smith says, "When I first started coming to Swim and Trim, I learned how to swim for the first time. Then everybody said, "Why don't you take the lifeguard course?' So I did.I passed the test and I still don't have any intentions of being a lifeguard; just having the knowledge is good. I've even gone as far as assisting teaching in a beginners' swimming class."

"We've had our problems," says Alexander. "Once a man fell off his bike and broke his thumb. We were halfway back to Washington from Mount Vernon. I had to carry his bike and mine to the 14th Street Bridge before help arrived. Everybody in the group seems to help each other. And we've a variety of people in the program's group: a judge, a few lawyers and dancers, a reporter, a federal official, teachers, secretaries, government workers, student, even a short-order cook, a dishwasher person and several lifeguards. We share a family and a kiddie day by picnicking together. It's more like one big happy family affair."

"Now on your feet for 75 jumping jacks," Alexander bellows as the group moans. They do 30. On the back row some cheat by moving only their arms and half-bending their knees. "None of this," Alexander illustrates, and the back rows corrects itself.

In spite of the efforts and the large community involvement, Swim and Trim remains an orphan offspring of the Capitol East Natatorium, meaning that the program doesn't get city funds.Alexander would like to see the program adopted; until that happens he doesn't have time to waste brooding, nor do the many men and women who participate.

"Okay," Alexander shouts again. "Straighten up those backs," he reminds the group as they finish the exercise session with 15 sit-ups. "That's it. You're looking good.

"And that," he says, "is my biggest reward."