DEAR DR. DONOHUE: My 14-year-old grandson sustained a fracture of his right collarbone while dirt-biking. He has to wear his arm in a sling for six weeks. He is a super athlete. What is his prognosis? Will it heal completely? Will it affect his ability to continue with his sports? – C.G.

ANSWER: The collarbone (clavicle) is the most frequently broken bone in childhood. It most often happens when the child falls on outstretched arms or when there is a direct blow to the bone. With such an injury, moving the shoulder on the affected side hurts.

Most breaks occur in the midportion of the bone. Wearing a sling is often the only treatment needed. Some doctors apply a figure-eight strap that crosses over the broken bone, comes down over the chest, is wrapped around the back and loops over the good shoulder.

Almost always, the bone heals without ever putting any limitations on the child’s future participation in any sport and without any effect on his or her athletic skills. There might be a noticeable bump at the fracture site, but that disappears in time.

DEAR DR. DONOHUE: I received your Fitness booklet, and the item on page 18 confuses me. It’s on how to do abdominal crunches. I find it impossible to raise the chest off the floor and raise the buttocks at the same time. I believe that’s what the instructions say. Would you clarify this for me? I am trying to strengthen my abdominal muscles. I am still beset by a stomach bulge that I can’t seem to reduce. – L.F.

ANSWER: Let me make the crunch less confusing. Incidentally, this exercise can be done in a number of different ways.

Lie on your back with your hands behind your neck. Your knees and hips are bent 90 degrees. It looks as though you are sitting on a chair, only your knees and legs are up in the air.

Contract the abdominal muscles while simultaneously lifting the shoulders off the floor. Hold that position and move the knees closer to the head. Don’t pull on your neck. Repeat as many times as you can without exhausting yourself.

Crunches, like sit-ups, are good for the front abdominal muscles. You also need to exercise the side abdominal muscles. One way of doing that is to perform a regular sit-up with a twist to it. The feet are on the floor, and the knees should be bent. Rise as though you were doing a sit-up but turn your right shoulder (right elbow if you keep your hands behind your neck) to your left knee. Return to the starting position and perform the next sit-up while turning your left shoulder (or left elbow) to you right knee. Ten to 20 repetitions are enough.

Abdominal exercises do strengthen the abdominal muscles. Strong abdominal muscles act like a girdle to hold the stomach in. They don’t, however, selectively remove fat from the abdomen. You have to reduce your daily calorie intake to accomplish that.

DEAR DR. DONOHUE: My daughter plays volleyball. I notice that her right shoulder blade sticks out. It didn’t used to. I have asked her to draw it back in, but she can’t. Could this be from her volleyball-playing? – M.M.

ANSWER: It could be. She could have stretched the long thoracic nerve, the nerve that supplies the muscles that keep the shoulder blade flush with the back. The injury has a name – long thoracic palsy.

Does she complain of any shoulder discomfort or weakness? Long thoracic palsy usually causes both.

It’s a frequent injury in sports that require players to stretch their arms over their heads – a motion that is required of volleyball players.

She should take a rest for a while and not lift anything heavy. She could stand some physical therapy. And most of all, she needs to consult the family doctor to make sure this diagnosis is correct.

DEAR DR. DONOHUE: My granddaughter has taken up swimming and wants to know if it’s possible to catch herpes or AIDS if a person with either disease is also in the water. – G.M.

ANSWER: Neither disease has been transferred by pool water.

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.