DEAR DR. DONOHUE: You wrote a column about abdominal exercises and wrote that sit-ups do not take fat away from the abdomen. Would you repeat what you said? – F.L.

ANSWER: Everyone wants to get rid of a stomach bulge, and everyone looks for the perfect exercise to achieve that goal. There is no perfect stomach exercise, but there are many good ones. And stomach exercises don’t selectively remove fat from the stomach. They remove fat from all fat deposits. That’s true of any exercise. Stomach exercises do strengthen the abdominal muscles. Strong abs keep the stomach flat by holding stomach organs in place like a natural corset.

Dr. Peter Francis of San Diego State University compared various stomach exercises to determine which is the best overall exercise and found that the bicycle exercise is best. It’s done by lying on the floor with the lower part of the back pressed to the floor. The knees are bent at a 45 degree angle. Then the legs move as they would move in pedaling a bike. When the right knee is in the pedal motion that brings it to the position that corresponds to the topmost position on a bike, bring the left elbow toward the right knee. And when the left knee is in that position, bring the right elbow toward it. Keep this up for as long as you can. If you can manage only two pedal motions at first, stick with it until you’re doing 10, 20 or more.

Second best on Dr. Francis’ list is the captain’s chair exercise. It calls for equipment found only in gyms, so I won’t give you the details.

Third is the crunch. You assume the lying-on-the-floor position and bend the knees to a 90-degree angle. Then draw your chest toward your knees. Return to the starting position and repeat as many times as you can. You can make this a little easier by resting your lower legs on the seat of a chair.

To flatten the stomach, you also have to flatten the inward curve of the lower back. Stand against a wall and assume a posture that gets the lower back as close to the wall as possible. Try to maintain that posture throughout the day.

Fat loss comes from aerobic exercise and calorie watching. Aerobic exercise is brisk walking, jogging, swimming, bike-riding or similar activities.

DEAR DR. DONOHUE: What, besides salt and sugar, is important in sports drinks to avoid dehydration and muscle cramps. Is there a recipe for making a similar drink to stay hydrated without it having any calories? – I.S.

ANSWER: To stay hydrated and to prevent cramps, water is a good drink.

If you exercise for more than an hour in hot weather and if you sweat heavily, you should replace sodium that’s lost in sweat. A simple recipe is to add half a teaspoon of salt and half a teaspoon of baking soda to a quart of water (approximately a liter).

If you want to get a bit fancier, mix a tablespoon of sugar (about 48 calories) with a pinch of salt in a tablespoon of orange juice and add the mixture to a cup of water. The sugar replaces the muscle sugar burned during exercise, and that prevents cramps and provides you with energy. If you’re working hard, you need the carbohydrate calories.

If you want a bigger volume of that homemade sports drink, four cups equals one quart.

Concerns about potassium, magnesium and other minerals are beyond the scope of a simple recipe. For those things you have to depend on commercial sports drinks.

DEAR DR. DONOHUE: I walk two miles a day. Is it more beneficial to walk every day or every other day? I would think it would be better to walk every day. Am I right? – G.P.

ANSWER: I’m with you. The experts tell us to exercise on most, if not all, days of the week.

DEAR DR. DONOHUE: I have become a nervous wreck. I went shopping at a store that has carts with a long pole on them so people cannot take the carts out the door. I reached into the cart for my bag and banged my head on the pole. After a few days, I had pain in my forehead and saw a doctor, who said I had a bump on my skull. I still get pain off and on. The doctor didn’t say much. I am scared. Please tell me what to do. – L.V.

ANSWER: The force on your head from bending over and hitting a metal pole is not great and is not likely to have caused serious damage. The bump could be a small collection of blood, like a bruise, under your skin. Damage to the skull or brain is close to impossible. Time will take the bump away.

If you still have pain, then see the doctor again. I believe, however, that you are worrying about something that doesn’t merit worry.

DEAR DR. DONOHUE: Do you approve of a nursing mother drinking alcohol? I am nursing my 3-month-old daughter. I like a couple of beers a day, especially in hot weather. My mother says I should not be drinking now. – R.S.

ANSWER: Wait until your baby is no longer nursing before you begin drinking alcohol again. It gets into mother’s milk. Even a trifling amount could be too much for an infant. Babies are small, and small amounts to them are actually big. Furthermore, the infant liver isn’t completely mature, and it can’t handle alcohol like a fully mature liver can.

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.