"Okay, up for one and hold. Now slooooowly let it down. Good."

Doralie Segal's voice is soothing and rhythmic as she guides her strength-training class in a series of leg lifts. She takes extra time and patience in building up these fragile bodies.

"It's okay if you wobble a little bit," she assures her students, who are all between the ages of 70 and 90 and recovering from strokes, heart problems, osteoporosis and a host of other ailments. "Now flex hard so you feel that tug."

The students' legs tremble with exertion during simple exercises with three-pound weights attached to their frail ankles. Sometimes they lose their balance. A few become frustrated and sore; others just laugh at the commands their bodies refuse. But they know they must get through the 50-minute session -- or the old fears of falling will creep back, stealing their newfound confidence.

The class at Iona Senior Services in Northwest Washington is less than two months old, and already there are success stories. One woman, 76, no longer uses a cane. Another woman, 71, proudly lifts three-pound metal dumbbells over her head, delighting in the clinking sound when they touch. Five weeks ago, she couldn't raise her arms.

Most of the 65-and-older crowd who sign up for classes at Iona and other local gyms aren't trying for bulging biceps or buns of steel. They seek simple exercises that will give them the muscle strength to carry their own groceries or get their shirts over their heads.

"I have felt very unstable in walking for some time," said Marjorie McPhillamey, 80, a District resident. "Now I feel a lot more steady. Falling is one of the very worst things that can happen to our peer group, but if you have balance and are steady, you don't worry about it as much."

Doctors hail the positive effects of weight training on the frail elderly, and medical studies show that regular exercise can increase mobility and help prevent the progression of osteoporosis.

With the graying of the baby boomers, gym managers predict that fitness for the elderly will become a priority. More than a dozen local gyms and community centers now offer low-impact workouts and other fitness services for seniors.

Kathy Zumbar, general manager of the YWCA fitness and aquatic center in downtown Washington, said the goal of exercise for the elderly is "functional fitness." More than half the center's members are at least 50, she said, and the Y has added an employee to its staff to organize programs for seniors this fall.

"There's definitely a growing interest," Zumbar said. "The medical field has readily acknowledged that fitness and exercise can improve the quality of life. Instead of prescribing blood-pressure medication or other medication, [doctors] say,`Hey, let's try this.'"

But exercise for any age group comes with risk of injury or overextension. Most health clubs with programs for the elderly require an evaluation before a fitness regimen can begin. At Iona, for example, arm and leg weights probably will never exceed seven pounds, and the class takes frequent rests between repetitions.

Segal, 69, the program director and a Senior Olympian, monitors fatigue and adjusts exercises accordingly. Some of the more frail complete their workouts while gripping a support beam.

Elsie B. Maddox, 90, is one of the oldest members of the class. She heard about it during a tai chi lesson. Her aching arms are proof to her that the exercise is working, and that gives her peace of mind -- which is better than any medicine.

"At my age, when you fall, that's it," she said, catching her breath after a recent workout. "At my evaluation before the class, I could get up and out of a chair, but the balance is gone. . . . I hope this brings it back."

CAPTION: Heather Siderius, left, a physical therapy student at Marymount University, coaches Charlotte Rosenberg, 90.

CAPTION: Marguerite Striar concentrates on dumbbells she uses during her weight-training class at Iona Senior Services. The class is about two months old.