DEAR DR. DONOHUE: I am going to be 20 soon. I have been athletic all my life. My problem is my height. I am only 5 feet 7 inches. Is there any chance that I will grow more? I am in college and am preparing to be a coach, but at my height, I don’t think I will ever get a job. I am a male. – G.H.

ANSWER: Most males stop growing – significantly, anyway – around age 18, but “most” does not mean “all.” Men and women can continue to grow well into their 20s.

Continued growth depends on whether bones have fused – become entirely bone. Before adult height is reached, there is an area of bone that remains cartilage. This permits bone elongation. When those plates of cartilage have turned into bone, further growth stops.

Adult height also depends, in large measure, on what your genes have programmed for you. You can get an idea of your genetic endowment from your parents’ height. If you want a rough estimate of your genetic destiny, you can use an often-quoted and often-erroneous rule. Add your mother’s and father’s height and then add 5 to that number. Divide the total by 2 to get an approximation of your adult height. (For girls, the rule is: Subtract 5 from the father’s height and then add the mother’s height. Divide that number by 2 to get the adult height guesstimate.)

If height is really bugging you, see the family doctor. The doctor can order an X-ray of your bones to see if they are fused or if there is still room for additional growth.

Why are you so sure that 5 feet 7 inches is a detriment to a coaching career? I don’t think you’re right about that.

DEAR DR. DONOHUE: Is there a set number of hours that should elapse from eating to exercise? I have always heard that you should wait four hours after eating to exercise. That’s very inconvenient for me. I can’t fit exercise into my day if I have to wait that long after eating to do it. – H.H.

ANSWER: It takes about four hours for food to leave the stomach. While it’s there, the body diverts blood to the digestive tract to aid in food digestion and absorption. If a person exercises, muscles clamor for more blood, and that sets up competition between muscles and the digestive tract for blood. A portion of blood is shunted away from the stomach and intestines to the muscles. That can lead to diarrhea and cramps.

A three-hour wait between meals and exercise is desirable.

The above information applies to a big meal, particularly one that has lots of fat. Fat slows the passage of food through the stomach.

For smaller meals and snacks, the time from eating to exercise does not have to be so long. An hour might be all that is needed, and perhaps even less than that.

Why must you exercise after you eat? Couldn’t you do it before?

DEAR DR. DONOHUE: I have arthritis in my neck. Doing sit-ups makes my neck really hurt. I keep my knees bent during the exercise. Is there any way around this? I need stomach exercise bad. – L.B.

ANSWER: I have a picture in my mind of you trying to touch your forehead to your knees. Am I right? If I am, stop doing that. All you need to do to get the benefit of a sit-up is to raise your shoulder blades off the ground. When you do so, hold that position for about five seconds before you lower yourself back down. People don’t gain any additional benefit by trying to touch their head to their knees.

Another thought comes to mind. Are your locking your hands behind your neck while doing your sit-ups? Don’t. Keep your hands on your chest.

When people lock their fingers behind their neck, they tend to pull on the neck when they raise themselves up in a sit-up. That puts a great deal of stress on the neck.

There’s nothing inherently wrong about doing a sit-up with the hands behind the neck. It’s a problem only for those with neck pain.

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.