DEAR DR. DONOHUE: I am 5 feet 7 inches and weigh 195 pounds. I am also a wrestler. My coach says I am too fat and that I need to diet. I am not fat. I am very muscular from working out year-round. I know if I lose weight I will be weaker. How can I convince my coach? – T.T.

DEAR DR. DONOHUE: I had a test called body composition testing. Electrodes pass a low level of current through the body. Is this a valid test for body composition? – D.F.

ANSWER: We are two bodies in one. One body is the lean body. Muscles, bones, organs and tendons constitute the lean body. The other body is the fat body.

Weight on a scale cannot tell a person if the weight is mostly lean body or mostly fat body. Distinguishing between the two has important health consequences. T.T. is a case in point. Most of his body weight is lean weight, so weight loss would not improve his health and would, as he says, make him less strong.

Some body fat is essential for health. If a woman’s body fat drops too low, her estrogen production wanes, and she can stop having periods. Both men and women need some fat for cushioning and as a source of stored energy.

Determining percentage of body fat can be complicated. One method is weighing a person on dry land and weighing the person when submerged in water. The difference between the two weights is used to calculate percent body fat. Measuring skin folds with a caliper is another test of body composition. The examiner pinches a fold of skin and fat at various body sites and then measures the width of the fold to arrive at body-fat percentage. D.F. had her body composition checked by bioelectrical impedance. Current passes more rapidly through fat-free tissue. The time it takes for current to travel from one electrode to a second gives an estimate of body-fat percentage. It is a valid test if it is done correctly.

What is a good percentage of fat? No one agrees. One accepted criterion is 18 percent to 23 percent for adult men, and for adult women the upper number can be 28.

DEAR DR. DONOHUE: I am a golfer and have been one most of my life. I have never had trouble playing until this past year. I have a terrible pain on the thumb side of my right wrist. What do you think it could be? – R.R.

ANSWER: My money would be on de Quervain’s disease. It’s an inflammation of the tendons that serve the thumb, and the site of pain is the thumb side of the wrist. The inflammation comes from overuse.

Bend your right thumb onto the palm of the right hand. Now bend your fingers so they cover the thumb. With your left hand, push the right hand toward its little-finger side. If that maneuver hurts, the odds for de Quervain’s disease are high.

Rest and anti-inflammatory medicines are the first line of attack. If the pain doesn’t stop in a week, get to your family doctor. The doctor can inject the inflamed area with cortisone and can provide you with a thumb splint. The splint gives the tendons an enforced rest.

Have you changed your swing? Right-handed golfers get de Quervain’s from an exaggerated straightening of the right thumb during the swing.

DEAR DR. DONOHUE: I am 19 and play in a softball league. I broke a rib sliding into second base. The doctor gave me painkillers and nothing else. My mom thinks I should be wearing a brace. Should I? – M.R.

ANSWER: If the two ends of the broken rib are in line and touching each other, then the goal of treatment is pain relief only.

Chest braces, binders and belts can make people more comfortable, but they can also discourage people from taking deep breaths. Shallow breathing can lead to collapse of a section of lung.

If the painkillers rid you of pain, then you really do not need anything wrapped around your chest.

DEAR DR. DONOHUE: I don’t know where to turn to, so I’ll turn to you. My family doctor says I have mitral valve prolapse, and he wants me to have a heart ultrasound. My brother had rheumatic fever, and it left him with a nonworking mitral valve. He had to have surgery. Am I destined for the same fate? – J.O.

ANSWER: The mitral valve lies between the upper left heart chamber – the left atrium – and the left lower heart chamber – the left ventricle. The left ventricle is the most muscular of all the heart chambers. It has to generate enough force to propel blood through all body arteries.

Mitral valve prolapse is not an unusual condition. It’s a valve that is floppy, and during a heart contraction, the valve balloons upward into the left atrium.

Often, a prolapsing mitral valve produces a typical murmur and a typical clicking sound. Both those signs alert the doctor to the possibility of mitral valve prolapse. The next step is to get a sound wave picture of the heart – an echocardiogram. It shows the ballooning valve and whether the valve is leaking any blood.

Your brother’s rheumatic fever is a much different story from your mitral valve prolapse. When rheumatic fever attacks a heart valve, it frequently leaves the valve deformed. A deformed valve either can lead to a leak, where blood returns to the left atrium rather than being ejected from the heart, or it can produce a narrow valve that makes it difficult for the left atrium to empty its blood into the left ventricle. In either case, surgical correction of the valve is often required.

If you have only a prolapsing mitral valve, it should not give you any problems.

If the prolapsing valve leaks blood, then the situation is a bit more significant, but not monumentally so.

Many people have mitral valve prolapse, and some of them develop abnormal heartbeats. Abnormal beats can also arise in those without a prolapsing valve. The explanation of such beats is given in the report on that subject.

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.