Luca Patuelli's hobbies reflect his 11 years of age: baseball, football and skateboarding. But when he plays with his friends, he plays on his knees.

"I tell them not to tackle me after I've thrown the ball but they do it anyway," Luca says, laughing.

Like most boys his age, the Rockville youngster thinks he is indestructible. He is outgoing and oblivious to the shortcomings of his disability, even though he has arthrogryposis, a disease that inhibits the development of his calf muscles.

If he had been born 30 years ago his parents probably would have been told that Luca would spend the rest of his life in a wheelchair or in bed. Physical therapy would have been advised, but the expectations for the quality of his life would have been kept low because there is no cure for his disease. Nationally, one in five Americans suffers from some kind of physical disability.

Today, however, Luca and other children and adults with physical disabilities can find facilities to exercise, get stronger and function at a healthier level. While the physical fitness craze of the '80s got boomers off the couch, physical fitness in the '90s is shifting to the next layer of society -- those with special needs, according to a report put out by the International Association of Fitness Professionals. Doctors, sports trainers and physical and recreation therapists are finding that under the right circumstances, exercise can boost the mental and physical well-being of people living with the aftereffects of spinal-cord injuries, strokes, cerebral palsy, spina bifida and many other disabilities.

"We know that exercise is only one part of the total care that a disabled person needs," says Charleene Frazier, a registered nurse who runs the exercise program at the Medical Illness Counseling Center in Chevy Chase, "but over time it is one of the more important parts."

In other words, fitness is not just for the able-bodied.

Frazier's program is one of the few in the area for paraplegics and quadriplegics. "The energy after exercising is incredible and their ability to handle anger, frustration and stress is much improved. The benefits are tremendous," Frazier says.

Across the street from the White Flint Mall in the basement of the Beco building, Luca participates in a fitness program twice a week for 45-minute sessions. Each session costs $60; a 30-minute express workout costs $40. There is no rock-and-roll or disco music blaring. Thongs are prohibited. And Barbie and Ken hard-body types are not hanging out by the Body Masters machines. It is small, private and quiet. And there are no mirrors.

"The truth is you really don't need them," says Marc Sickel, the owner of Fitness for Health and one of two athletic trainers who operate out of the private gym. "Mirrors put people in an intimidating situation." He says that if a person is seriously overweight or has a physical disability, he already knows it and doesn't need to be reminded of it by seeing his image multiplied around the room.

Sickel majored in kinesiology at the University of Maryland, is board certified and was an athletic trainer at Landon School in Bethesda. His three dozen clients range in age from 7 to 80.

"We work with the deconditioned market," says Sickel. "It's low-key, not flashy. It's a long road, but if you put people in a comfortable environment, they start to take control and build self-confidence. That's when they start to feel good about themselves."

Many of Sickel's clients are referred to him by psychologists, physical therapists and nutritionists. Before accepting a client, he conducts an extensive physical evaluation that lasts one to 1 1/2 hours and costs $165. In addition, he offers a group rate of $90 for two people per session.

Wearing a red Montreal Expos jersey and navy blue shorts, Luca Patuelli bends over and puts his hands just above his kneecaps. He then swings his upper body and legs and walks to the treadmill. The lower parts of his limbs are sheathed in white plastic braces that run from the top of his knees to his ankles. When he goes to class at Westland Middle School in Rockville, he wears braces that support his legs from hip to ankle.

When he started coming to the gym more than a year ago, Luca walked on the treadmill for 40 seconds at one mile an hour on a flat grade. He now walks 11 minutes at one mile an hour at an 11 percent grade. At first, Luca's legs felt soft and flabby, but now have begun to harden.

After using upper body weight machines, Luca stretches his lower limbs on the leg-curl machine for about six minutes. His workout goals are like most people's: Increase circulation, flexibility and strength. At 4 feet 3 and 45 pounds -- still behind boys in his own age group -- he has gained an inch in height since starting his exercise program.

Luca works out at home on a stationary bicycle, but his parents say they can't push him the way Sickel does. "I feel more motivated and stronger," Luca says. "It's like I know what I'm doing, and I can direct my body where I want it to go."

Luca's father, Flavio Patuelli, is negotiating with his insurance company to pick up the costs of Luca's sessions. "Luca is not mature enough to force himself to do the exercises that Mark makes him do," he says. "He needs Mark to challenge him."

A large blackboard hangs above the doorway of the Achilles Track Club. In pastel chalk someone has handwritten, "IF IT'S TO BE, IT'S UP TO ME."

What with two television sets going, NordicTracks clanking, Stairmaster machines humming and basketball teams playing on the other side of the workout warehouse, the club is pumped to the max.

The club is housed in the Aspen Hill Racquet Club and Fitness Center, which has an indoor pool and indoor and outdoor tennis courts. And every Friday night from 6 to 8:30, adults and children with disabilities and a doctor's permission slip can work out for free.

Volunteers are trained to work one on one with people who have cerebral palsy, use wheelchairs, have had strokes or are vision-impaired. Members with disabilities who can work out by themselves have access to the club between 11 a.m. and 4 p.m. during the week at no charge.

Robert Watson and his wife, Lynn Robertshaw, who both have cerebral palsy, went to Achilles on their first date. "Self-confidence is a whole gigantic issue for the disabled who regularly work out," Watson says. At the club "you are with other people who are not disabled, and it is totally integrated. It helps when people come up and tell you you did a good job. It is just a tremendous boost to your self-confidence."

Watson had just attended a conference in Toronto where the issue of exercise and disability was debated. "The consensus was that exercise of some sort is great for you, but nobody knows yet what role exercise can play in {overcoming} a person's disability," he says. "There is also that other school of thought that argues that exercise can wear down a handicapped person's reserves."

Laura Stillwell has been working out at Achilles since the club opened eight years ago. She uses the weight machines once a week in the summer and three to four times a week in the winter. Her mild cerebral palsy affects the right side of her body. Exercise has improved her motor coordination. She is able to walk straighter and for longer periods of time.

"When I was growing up I used to dwell on my disability and how I was different from other people," Stillwell says as she conducts a tour of the gym. "I quit doing that a while ago, and now I look at myself like I'm just like everybody else."

Recovering from a stroke he had several years ago, 70-year-old Irv Lipskind can now lift and push about 60 pounds on the weight machines. When he first started he could only lift the bar. "Exercising makes you feel more human. You're not on the sidelines anymore, and you can do things up to your potential," he says. Nancy DiBenedetto, a therapeutic recreation specialist who has worked at the National Rehabilitation Hospital for eight years, says people with disabilities don't always want to learn how to exercise soon after an accident or trauma. "It takes about a year for a person to get used to the fact that they need to do something," she says. "Then they come {here} to find out what they can do. We absolutely encourage exercise."

DiBenedetto currently works with 10 patients. Every Tuesday morning for two hours, they use the indoor pool at the YMCA at 17th Street and Rhode Island Avenue NW for free. Recreation therapists fill a transitional role, helping inpatients become outpatients. Sessions with DiBenedetto cost about $135 an hour.

"They don't want to exercise by themselves. They want to learn how to exercise with their family and friends," she says. "The key to an individual exercise program is to try and use the facilities in your back yard."

DiBenedetto's boss has taken that advice and then some. As president of NRH, located in Northwest, Edward Eckenhoff is proof that a disability is what you make it. A 1963 automobile accident damaged his spinal cord and left him a paraplegic. Today he is an avid golfer with a 16 handicap. When he isn't running the 10-year-old hospital, Eckenhoff advises Fortune 500 companies on how to blend the requirements of the Americans With Disabilities Act into their corporate strategies.

While Eckenhoff competes in golf, many other paraplegics and quadriplegics have learned how to work out on stationary bicycles. According to the Medical Illness Counseling Center's Frazier, anyone can be trained to cycle. She has taught family members and caretakers how to get a patient in and out of a wheelchair and hooked up to the bicycle, which electronically stimulates the leg muscles to turn the wheel.

Depending on the severity of an injury, a person can learn to cycle six months after trauma. A two-hour session at the nonprofit center costs between $130 and $155. Frazier, who takes only patients from Maryland, says Medicare covers some of the costs.

Some of her patients have bought bikes to use in their homes. While the cost, $9,000 per bike, sounds steep, Frazier says it should be looked at as an investment.

"The immediate effect for the patient is that they are more comfortable because they are not sitting on wasted muscle. Pressure sores are a big problem," Frazier says, "and when you look at the fact that a single stay at a hospital can cost $75,000 to treat a breakdown in the skin, then the bicycle doesn't sound exorbitant."

Of the 10 patients she oversees, four have been exercising for a decade. Three of those four are quadriplegics and one is a paraplegic. Their hard work has paid off. "Other than the usual bout with the sniffles, they haven't been sick once during that time," says Frazier.

Exercise will not reverse any of these disabilities. Luca will probably wear braces for the rest of his life. Laura Stillwell and Robert Watson will have cerebral palsy for the rest of their lives. And Edward Eckenhoff's golf game may improve, but his spinal cord injury will not disappear.

It takes a long time, sometimes three to five years, sometimes a whole lifetime, to learn how to live with a disabled body and make it work differently from the way it was designed to work.

But exercise gives the disabled a measure of independence and a chance to improve the quality of their lives by strengthening their immune systems, alleviating depression and restoring energy where it once seemed to be lost forever. CAPTION: "I feel more motivated and stronger," says 11-year-old Luca Patuelli, working out on the treadmill under the guidance of Marc Sickel. "I can direct my body where I want it to go."