DEAR DR. DONOHUE: This week, while pitching for his high-school baseball team, my 15-year-old grandson broke a forearm bone. It was the ulna at or near the growth plate of the bone. The doctor said it might interfere with further growth of his arm.

Our grandson has had a rapid growth spurt. He is 6 feet 3 inches tall and weighs 165 pounds. He will have surgery to pin the break.

How does this kind of thing happen? How can it be prevented? Does rapid growth weaken bones?

— J.M.

DEAR J.M.: I had to get help from a distinguished orthopedic surgeon on this because it is such an unusual injury. I have no experience in handling it.

Growth plates are cartilage sections of growing bones. They allow the bone to elongate. When growth stops, the growth plate has become solid bone. Growth plates are points of bone weakness.

A rapid growth spurt does slightly weaken the growth plate even more.

Your grandson is 6 feet 3 inches, so he must be nearing the completion of his growth. If that is the case, then there should not be a great disparity in the lengths of his arms.

Did he complain of arm pain before the break occurred, or did it come without any warning? Overuse of his arm might have been a major factor in this accident, but high-school baseball coaches usually are quite vigilant about limiting the number of pitches a teenager throws during a game, during a week and during the entire season. If the boy had pain, then the break might have been avoided. I'll bet he had none, and this was sort of a freak accident.

Parents should not worry about their sons or daughters suffering the same kind of injury. This is truly a rarity. Parents should inquire if the school keeps a record of pitches thrown.

DEAR DR. DONOHUE: I think you answered this question, but I forgot what you said. Is it possible to lose weight from exercising only — without dieting?

— R.B.

DEAR R.B.: It's possible to lose weight through exercise alone, but it takes lots and lots of hard exercise to accomplish that.One medium pear has about 100 calories. Most of us don't think of a pear as being fattening. However, to burn 100 calories, you have to walk at a speed of 4.5 miles an hour for 22 minutes. That's walking very fast.It takes 11 minutes of rope jumping, 13 minutes of singles tennis and 11 minutes of strenuous swimming to burn 100 calories. Not many people are up to this amount of exercise.

Exercise and dieting go hand in hand. Exercise does burn some calories. More importantly, it prevents loss of muscle tissue that comes with calorie restriction. A combination of exercise and calorie reduction is the best way to lose weight.

DEAR DR. DONOHUE: What's considered ideal pool-water temperature? In our apartment complex, there is a large pool that is so cold I rarely use it. I am getting a thermometer to measure its temperature. I would like to have a reference temperature to present to management if the water is colder than it should be.

— N.U.

DEAR N.U.: Pool water is comfortable for most when its temperature is between 82 and 86 degrees F (28-30 C). The water is cool enough to keep strong swimmers from overheating, but warm enough to keep floaters from freezing.
