DEAR DR. DONOHUE: Please straighten out the salt issue out for me. Some say that you should make sure to eat salt when you run on a hot day. Others say just the opposite. They say eating salt upsets your stomach. Which is the correct instruction? – B.J.

ANSWER: Over the years, the salt recommendations prior to and during exercise have swung back and forth, so I understand your confusion.

Not too many years ago, the instructions for exercising in hot weather were to take salt tablets. At that time, the amount of salt in the tablets was quite high, and the tablets irritated the stomach. They created more trouble than they prevented, so the salt-tablet idea faded. Instructions then were to load up on water before a prolonged exercise session and to keep drinking it all through the exercise session.

However, more recently the necessity for salt when exercising for a long period in hot weather has been resurrected. In the 2002 Boston Marathon, a 28-year-old, healthy woman died after the race. Dehydration was not the cause of her death. Hyponatremia was. Hyponatremia is a low level of salt in the blood.

Hyponatremia can lead to brain swelling, and that swelling, in turn, can lead to death if the sodium deficit is not corrected.

Today the guidelines for such marathon-type exercise urge that salt be used before and during the exercise. An eighth of a teaspoon of salt in 1 quart (liter) of water is enough. That amount is not so great that it makes water unpalatable. If you want, drink the many sports drinks available. They all have salt in them.

Don’t load up on water before the exercise, and don’t keep drinking water compulsively during the exercise. Drink two or three glasses of lightly salted water two hours before exercising in the heat and a glass or two every half hour while exercising.

DEAR DR. DONOHUE: I am an 80-year-old woman with a dropped bladder. Can I go swimming in a pool that has chlorinated water? – S.G.

ANSWER: How far dropped is your dropped bladder? If it protrudes through the vagina, then experiment. See how the chlorinated water affects it. If it does not hurt, then you can safely swim in such water.

If the bladder does not protrude through the vagina, you can swim without concern.

DEAR DR. DONOHUE: Not always, but somewhat frequently I get a pain on the right side of my abdomen below the ribs when I run. Why does it happen, and what can I do to prevent it from happening? – D.T.

ANSWER: The pain you get is called a side stitch. I bet every single person on Earth has experienced a side stitch at least once.

There are many explanations why side stitches appear. Some say they are due to a cramp in the diaphragm, the broad sheet of muscle that separates the chest from the abdomen. The diaphragm happens to be the principal breathing muscle.

I have a collection of home remedies that have been sent to me through the years by people plagued with side stitches.

When you get a side stitch, stop running. Bend over and contract your abdominal muscles or put finger pressure on the painful site. Make certain to take full breaths. You can tell if you are taking a full breath if your stomach sticks out when you inhale.

My favorite suggestion is the following: If the pain is on the right side, exhale when the left foot strikes the ground. If the pain is on the left side, exhale when the right foot strikes the ground. I have no idea why this should work. I don’t know if it does work, but many letter writers insist it does.

DEAR DR. DONOHUE: I can only exercise in the evening after dinner. How long after eating should I wait to do so? – G.P.

ANSWER: After a large meal wait three to four hours. After a smaller meal, hold off on exercising for two to three hours. After a purely liquid meal, you can exercise in one or two hours.

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.