Tara Laszlo, a 16-year-old in St. Paul, Minn., is a speedskater. She races on long-bladed skates, zooming along the ice as fast as she can go. Speedskating is a power sport -- and training for competitions is tough work. Tara sticks to it because she has a goal: She hopes to compete in the 1988 Olympics.

Tara's dedication and skill will probably win her a place on the U.S. Olympic Speedskating Team. But not long ago it looked as if Tara might have to give up her beloved sport.

A couple of seasons ago, she started having a problem. It happened every time she went out on the ice to practice. At first, everything would be fine. Then, Tara would break out into uncontrollable coughing. She would feel as if she couldn't get enough air into her lungs, no matter how hard she tried. She had to stop skating and rest.

Tara's doctor told her she had exercise-induced asthma. But the diagnosis did not spell the end of her career as a speedskater. Tara's asthma has been successfully treated, and she's probably practicing her skating right at this very minute.

Not so long ago, Tara probably would have had to give up her dream of becoming an Olympic champion. But times -- and treatments -- have changed. Today, doctors believe that exercise is just as important for people with asthma as it is for people whose lungs work just fine.

Exercise-induced asthma happens when cool, dry air enters ultra-sensitive air passages in the lungs. Normally, we inhale through our noses, and the air passes through narrow passages where it gets cleaned, warmed up and moistened before it meets delicate lung tissue.

During exercise, we tend to take large gulps of air through the mouth, and it goes straight to the lungs without getting the moisture- and-warmth treatment. The result, in sensitive people, can be an asthma attack.

When that happens, muscles around the air passages in the lungs contract. The airways get narrower, allowing less air to enter the lungs. At the same time, the surfaces of the airways swell and start producing extra mucus. The wheezing sound of an asthma attack is the result of air whistling through the narrow passageways. Coughing fits start as the body tries to get rid of all that extra, gooey mucus.

Doctors now know that allergies can also trigger asthma attacks. Dust, pollen, animal fur, cigarette smoke and other irritating substances cause chemical reactions in the lungs, bringing on the shortness of breath, coughing and wheezing.

In recent years, researchers have developed effective medicines to treat asthma. Some of the drugs prevent attacks from getting started; others treat the symptoms of an attack once it has begun. Some asthma patients also get allergy shots designed to make them less sensitive to the irritating substances that bother them. In spite of good treatments, asthma is a serious condition.

Each year, asthma causes children to visit hospital emergency rooms or miss school days more often than any other chronic illness. In the United States, more than 15 million people have asthma. The author of this column is one of them.

When I was in school, I avoided taking part in running games. When I did run, I quickly got out of breath, felt wheezy and started coughing. I felt like I couldn't get enough air into my lungs. Some kids teased me and said I was out of shape. I wasn't; I was having asthma attacks.

Now that I'm grown up, my asthma is still treated by a doctor. I take medicine every day, and my breathing problem is under control. I have even started playing running games like tennis and softball!

Before the activity, I use an inhaler that contains medicine to prevent an asthma attack. To help my lungs stay clear I also avoid things that I know cause me trouble like cigarette smoke, perfume and aerosol sprays. If I feel short of breath, I follow my doctor's advice: "Feeling wheezy? Take it easy."

I go to the doctor to have my lung capacity checked regularly. It's an easy test: I take a deep breath and blow out as hard as I can into a device that records how much air my lungs can hold. "Normal," the doctor says after he compares my performance to the average lung capacity of a person my age, height and weight. Phew! That's a relief!Tips for Parents

Knowing early signs of an attack can help parents keep a child's asthma under control, says Dr. Thomas Plaut in "Young Health," a publication of the American Academy of Pediatrics. Dr. Plaut describes the four signs of asthma trouble: wheezing, sucked-in chest skin, exhaling longer than inhaling and rapid breathing. Even earlier signs include exercise-induced coughing or wheezing and laughter that brings on wheezing.

How can parents tell if a child has asthma? The signs are often subtle, but coughing at night or coughing with exercise should cause suspicion, especially where there is a family history of allergies or asthma. For more information about asthma and allergies, contact the Asthma and Allergy Foundation of America, 1717 Massachusetts Ave., Suite 305, Washington, D.C. 20036; phone (202) 265-0265.Catherine O'Neill is a free-lance children's writer in Baltimore.