February used to be just for valentines. Now it's also the month for hearts. As part of its celebration of "Heart Month," the American Heart Association has selected 12 of Washington's healthiest and heartiest citizens.

In their search for the 12 heartiest Washingtonians, seven volunteer judges reviewed more than 200 candidates, nominated by an admittedly informal process. The criteria were simple:

The candidates do not smoke, they exercise daily, they maintain proper weight, and they are careful about their diets.

What sets the 12 apart is the public aspect of their dedication to fitness. Dr. David L. Pearle, a cardiologist and president of the District chapter of the American Heart Association, says he hopes the list will become an annual event -- a way to honor people for their good habits.

"We want to give other people ideas of what kinds of things might be done," says Pearle, himself a marathoner. "By their example, the 12 influence others to pursue a heart-healthy life style." Lacey O'Neal: Olympic Hurdler

* When Lacey O'Neal was competing as a hurdler in the 1964 and 1972 Olympic games, superbly conditioned women were less common than they are today. "It used to be that femininity was associated with weakness, and that muscles on a woman were ugly," she says. "Not anymore. Now men are proud to say, 'My woman is strong.' "

For the past year, she has been trying to reinforce the changed attitudes about fitness by training employes from the D.C. Department of Recreation to run fitness classes for District employes.

While O'Neal, 40, no longer competes, she keeps in shape by taking aerobic dance classes, lifting weights and running. "I eat moderately, but I eat everything," she says. The combination of diet and exercise gives her results she likes: looking and feeling young. Maureen Bunyan: Television Anchor

* In a field as competitive as television news, the pressures to look good often rival the pressures to perform, especially for a woman. But it's the internal benefits of fitness, not just the external ones, that keep Maureen Bunyan on the move.

The head and shoulders of WDVM's news anchor are familiar to many metropolitan area viewers. But Bunyan's television image doesn't reveal her confident gait, erect posture and clear eyes.

Three times a week, Bunyan, 40, heads for her exercise class. On weekends, she speed-walks and hikes with friends.

The best thing, though, is that she feels better -- younger and more energetic -- than she did five years ago.

"A lot of young people ask me how to begin a career in broadcasting, but what they really want to know is how to get to a point in life where they'll get recognition," the Channel 9 reporter says. "I tell them that nothing happens instantly, and I try to show them the processes, such as writing a resume, that must take place.

"It's the same with fitness. Everything builds on the step before." Pam Briscoe: Marathon Runner

* As Pamela Briscoe ran the first miles of the Marine Corps Marathon last November, she didn't expect to win. Only as the race progressed, and she heard the spotters call out the times, did she realize that victory was within reach. She abandoned her prudent goals for the day and gave the race everything she had.

When the race was over, "I was dead," Briscoe recalls.

But triumph is addictive, and as she trains now for the Boston Marathon in April, her goal is to finish in less than 240 minutes -- beating the 243.20-minute race that won her first place here.

Briscoe, 29, started running marathons in 1979 after a challenge from her friends. After the 1981 Marine Corps Marathon, she asked Jim Hagan, a friend from the Washington Running Club, to coach her.

"Having Jim as a coach is a big part of why I'm still racing," she says. "It really helps to have someone else out there." Desi Alston: Symphony Violinist

* I t's not everyone's idea of fun: a 2.4-mile swim in the ocean, a 112-mile bike ride over steaming lava fields, and then a quick marathon to top off the day. But Desimont Alston, a violinist with the National Symphony Orchestra, did it all last October during Hawaii's Ironman Triathalon. He completed the race in an impressive 14 hours, a little sore, but smiling.

He's smiling still. The 33-year-old musician has run every day for the past five years. He eats no red meat and very little fish or poultry. He indulges his sweet tooth in moderation -- having only a pint of ice cream or a handful of his favorite oatmeal raisin cookies from time to time.

His fitness routine also prepares him mentally for the discipline and concentration required by his other love: the violin. "After I have my run, I'm usually willing to put in the time and practice," he says. "I feel like I have a lot more mental stability, more aggressiveness." A. James Clark: Corporate President

* If incentive is important in breaking the smoking habit, employes of Clark Enterprises have it made.

The corporation's president, A. James Clark, instituted a no-smoking policy within the offices. Employes still may smoke in the lobby or outside the building. But Clark also adds a carrot along with the no-smoking stick: He'll pay the fees for workers to go to smoking cessation classes.

Clark, 57, takes exercise seriously, too. He rises at 5 a.m. every day and spends two hours working out in a small gym in his Easton, Md., home. Or, if weather permits, he may take a spin on his bike or slide his scull into the Miles River and row a few miles.

"Exercise is labor at first, but once your body gets used to it, it's exhilarating," he says.

And he's installing a health club in his new corporate offices in Bethesda for the exclusive use of the employes of Clark Enterprises subsidiaries, Omni and George A. Hyman construction companies, and those of his tenant, the Wang Corp.

"Everybody tells me, 'I don't have time for exercise,' " says Clark. "This is hard to say, but there are hardly any executives any busier than I am. And I have time. You have to make it." Janet Reed: Exercise Specialist

* Janet Reed has been called the "Jane Fonda of the wheelchair set." Like Fonda, she had adopted both music and attractive workout garb to make regular exercise more enjoyable.

Reed, 49, has thoroughly adapted her life to make the best of her misfortune and makes it look like fun.

Since she was thrown from a horse in 1977, she has been without normal sensation or movement below her waist. While she had given up some of her favorite activities, Reed's physical disability has not diminished her pleasure in dancing and being active.

In fact, it was her love for dancing that, in 1983, led her to produce "Wheelchair Workout," a 30-minute exercise-to-music program. The exercise program, which comes with a cassette tape and an instruction booklet, has reacquainted thousands of disabled people with the pleasures and benefits of fitness.

"I don't claim cures or improvement," Reed says. But since she has been working out regularly, Reed reports better balance, stronger abdominal muscles, greater ability to move her torso, and "better awareness of what my body can and cannot do.

"Fitness is important, not only because you're keeping in better shape, but you're keeping your body ready for that time when there's a cure for the disability or disease or injury," she says. "No one knows what tomorrow will bring. But in the meantime, don't put your life on hold." Linda Carter: Actress

* The final segment of "Wonder Woman" was completed five years ago, but time has not dulled the character's appeal or lessened her strength.

Lynda Carter, 33, had little difficulty playing the part of the confident, sleek, strong Wonder Woman.

"Even though I would prefer that people think of me in a different context, Wonder Woman's image has been beneficial to a lot of people," Carter says. "She heightened the female image. She was not a pushy person. I could have made her tough, but I never wanted to. I wanted her to be smart."

Part of being smart, Carter contends, is paying attention to fitness. She often race-walks along the C&O Canal, or rides her bicycle.

"If you can work out in the morning, I think that's the best of all," Carter says. "You feel great about yourself all day long. You've done something for yourself."

In her speaking engagements for charities, Carter encourages parents to set an example for their children, as her parents did for her. "I believe that with a strong backgrounds, kids go back to basics," she says. "Despite all the junk food, they remember what they need to survive, what makes them the healthiest." Beverly Byron: U.S. Representative

* Rep. Beverly Byron (D-Md.) entered Congress in 1979, after her husband, Rep. Goodloe Byron, died of a heart attack while jogging. No one was surprised when the usually independent, fledging legislator followed her husband's example in at least one area: She became a tireless champion of health and fitness.

One of her major goals, Byron says, "is to get Americans to think more about staying in shape." She believes that school children should receive more fitness training than they do, because a person who develops a good fitness habits as a child is more likely to maintain fitness as an adult.

Even with the relentless demands of her job, Byron, 52, still finds time to jog each day, "not terribly far or fast," and to escape for an occasional bicycle trip or for a hike with her family. Although her husband died while exercising, she believes that given his heart condition, he lived longer than he would have were he in poor physical shape. Colman McCarthy: Journalist

* Colman McCarthy would be a lot happier if the world were in as good a shape as he is.

For the syndicated Washington Post columnist known for his arguments against militarism, fitness has become a way of thinking. At 46, he has run 18 marathons. He also rides his bicycle to work, a total distance of about 50 miles each week.

"I consider the planet my health club," he says. "God starts most of us out with a healthy body in fairly good working condition. Either we take that gift and use it well, or we take the gift and destroy it."

McCarthy is a vegetarian and drinks neither coffee nor tea. Nonetheless, he says, he is not obsessive about fitness and enjoys ice cream and candy. "I junk it up with the best of them."

In McCarthy's view, the greatest threat to fitness is neither sloth nor junk food, but militarism. "You really can't think about physical fitness until you think about planetary fitness," he says. He advises anyone wishing to begin a fitness program to read a little bit of Gandhi, some Tolstoy, and perhaps some Dorothy Day and Thomas Merton, Eachled a healthy life, and each was a pacifist. Samuel Fox: Cardiologist

* Samuel Fox has seen the extreme effects of fitness and flab more than most people. After years of examining and treating patients with heart disease as a Georgetown University Hospital cardiologist, he is convinced that "there's no doubt that we should encourage people to take preventive action."

But he thinks fitness should be fun and not just done to ensure a healthy heart.

At 62, Fox manages to have a little fun himself. He occassionally hauls out his bicycle and pedals the seven miles to work, and he fits frequent tennis games into his hectic schedule.

His latest passion is windsurfing, although his slender, lanky frame doesn't fit the windboard too well. "I'm built all wrong for it," he says. "But it's enough just to go out and enjoy the pleasant things in nature." Sugar Ray Leonard: Former Boxing Champion

* It doesn't seem quite fair, but neither an Olympic gold medal nor a world boxing championship prevents America's most pervasive affliction: flab. Since he left professional boxing -- and the trainers that went with it -- Sugar Ray Leonard, 28, has been working out like the rest of us.

Visitors to suburban Maryland high school gyms may meet Leonard and assorted friends at pickup basketball games at which Sugar Ray's Church's Chicken Champs get their practice. The informal team pits itself against local high school basketball teams in a tough schedule of benefit matches. The proceeds go to the high school's athletic or music programs.

Leonard says his team is a "natural." It helps the schools, and it helps him to stay in shape. He also runs a couple of miles two or three times a week, and he is building a small gym in his basement.

Occasionally, Leonard visits gyms, and may briefly act as an impromptu coach to aspiring boxers. But these days, he prefers to spend his time on the outside looking in.

"Kids identify with someone they admire," he says. He lent his name to a boxing gymnasium in Palmer Park, Md., and participated in the American Heart Association "Jump Rope for Heart" promotion in the public schools.

He encourages youngsters to follow his example: Turn on their favorite music while they exercise, and have a good time. Says Leonard: "Any type of exercise becomes difficult of you think about it too much." Dan Quayle: U.S. Senator

* The statistics of health care are as familiar to Sen. Dan Quayle (R-Ind.) as the course he runs four times a week near his McLean home.

U.S. health care costs increase from $26.9 billion in 1960 to $322.4 billion in 1982. Quayle, 38, believes that one way to reduce these ballooning costs is to raise the public's awareness of disease prevention through routine check-ups, exercise and attention to diet.

"If Americans will take fitness seriously, then we're going to have a much more productive society than we have today," he says.