DEAR DR. DONOHUE: I am bothered by muscle cramps in my calves during practice and during games. They don’t happen all the time, but they happen enough that it bothers me. I have to stop playing when I get them. Coach told me to eat a teaspoon of salt a day. Will that stop them? – B.C.

ANSWER: People have argued long and loud about the causes of muscle cramps, but no one has definitely settled the issue. Researchers in South Africa examined participants in a triathlon. That’s a contest with successive events of swimming 2.4 miles (3.9 km), biking 67 miles (108.2 km) and running 26 miles (42.2 km). At the end of competition, blood from those who suffered muscle cramps and those who did not was checked for sodium, potassium, chloride, magnesium and sugar levels. There were no differences in the levels between the two groups. That appears to blow a hole in the theory that muscle cramps come from a deficiency of one of those minerals or from a drop in blood sugar.

The contestants were also tested, at the end of the contest, for their state of hydration. Again, there was no difference between the crampers and noncrampers, so fluid loss is not the cause.

Stop taking the teaspoon of salt. That’s too much salt for anyone to eat. If you want to experiment, put some salt – perhaps a quarter of a teaspoon – in 16 ounces of sports drink and use that for replenishing salt. I don’t think it will work, but you can humor your coach by doing so.

Most authorities believe that cramps come from muscle fatigue that triggers abnormal motor activity in the muscle.

If you have an inkling that a cramp is about to occur, briefly stop and massage the muscle. Some believe that stretching before exercise might prevent cramps. That idea, however, has not been proved. I apologize for giving you only negative information.

DEAR DR. DONOHUE: I am the guardian of a 13-year-old boy who shows signs of Marfan’s syndrome. How can I find out if he really has it? He is 6 feet tall, very thin and has long fingers and toes. – K.M.

ANSWER: Marfan’s is a genetic illness with some fairly distinctive physical features. People with the syndrome are tall and have long, thin arms and legs. Their fingers are elongated and tapered. They often have loose joints. They might have a deep depression in their breastbone, or the bone might stick out.

The dangerous changes of Marfan’s are internal. It can cause the aorta – the largest body artery – to be dilated and somewhat flimsy. The aorta can rupture when Marfan’s patients are engaged in vigorous exertion. You might recall the story of the Olympic volleyball player who lost her life during a match due to a ruptured aorta. No one had recognized that she had the syndrome. The external features can be quite subtle.

Take the boy to the family doctor. If the doctor thinks Marfan’s is a possibility, he or she can order an echocardiogram to detect any changes in the aorta. The echo can also reveal leakages in the aortic and mitral valves, two other conditions frequently found in Marfan’s.

DEAR DR. DONOHUE: I manage a gym that has many older clients. I asked my boss, who is seldom around, if we could get a defibrillator in case someone has a heart attack. He doesn’t think it’s necessary. Do you? – R.R.

ANSWER: I think having an automated external defibrillator in places where a cardiac arrest is a possibility is an excellent idea. A gym is such a place. The defibrillator analyzes a stricken person’s heart rhythm and delivers a shock if that person has a rhythm that requires one. Many sudden heart deaths are due to ventricular fibrillation. The ventricles are the pumping heart chambers. “Fibrillation” means they are quivering and not beating. A shock can usually restore normal heart rhythm and normal pumping action to a heart in ventricular fibrillation.

Ventricular fibrillation is not the same condition as atrial fibrillation, a much more common heartbeat disorder and one that does not usually carry the threat of immediate death if the abnormal beat is not terminated quickly.

Dr. Donohue regrets that he is unable to answer individual letters, but he will incorporate them in his column whenever possible. Readers may write him or request an order form of available health newsletters at P.O. Box 536475, Orlando, FL 32853-6475. Readers may also order health newsletters from www.rbmamall.com.