Dear Dr. Donohue — Can you figure out what's going on with me? I have been a daily runner for a number of years. I mostly run on a treadmill in an air-conditioned gym, especially in the summer months. This year, I am having breathing troubles. About six or seven minutes into my run, I start coughing and feel like there's a tight strap around my chest. I have to slow down or stop. The strange thing is that when I run outside, none of this happens. Why? — S.J.

Answer — You make a good case for exercise-induced asthma. During an asthma attack, the bronchi — the airways — constrict. Simultaneously, they start pouring out thick mucus. Both make the passage of air into and out of the lungs most difficult. It's a bit like being choked. People begin to wheeze, cough and struggle to get enough air. Chest tightness is another symptom.

Troubles usually arise after about 10 minutes of fairly intense exercise. If a person can continue, symptoms often lessen. I'm not telling you to persist. It's wiser to stop to avoid possibly developing greater breathing difficulty.

Those already diagnosed with asthma and under treatment for it have this problem. They're prepared for it. They take medicines before exercise.

The reason why you have symptoms in the air-conditioned gym but not outside most likely is due to the cooler, dry air of the gym. That air triggers airway constriction. Warm, moist air is less likely to do so.

You cannot depend on my guess to start treatment for exercise-induced asthma. The diagnosis has to be proven. That's best done in the doctor's office. The doctor has you take a breathing test before you exercise, and then has you exercise on a treadmill. When symptoms appear, he or she gives you another breathing test. A change in the amount of air getting to your lungs indicates the airways have constricted.

Medicines can prevent these attacks. Inhaling a medicine like Proventil 10 minutes before exercise keeps the airways opened. Or you can take an oral medicine like Singulair. You have to take it at least two hours before exercising, but its effects last for a full 12 hours. Or you can skip all this and limit yourself to outdoor running in warm weather.

Dear Dr. Donohue — I have trouble with weak ankles. I am always twisting one or the other.

Which is better for me — tape or an elastic brace? — T.J.

Answer — I take you to mean you have this problem when you're jogging or running.

An elastic wrap provides longer-lasting support for the ankles than tape does. Tape loses its gripping power somewhat quickly.

Write Dr. Donohue at P.O. Box 536475, Orlando, Fla. 32853-6475.