DEAR DR. DONOHUE: Will you settle an issue that has come up about throwing curveballs at a young age? My son is 12 and is a truly excellent pitcher. He begged me to show him how to throw a curve. I did, and he learned the technique quickly.

Fathers of other boys in his league tell me he will ruin his arm by throwing curves. His coach hasn’t said anything. I need a definite answer about this. I don’t want to ruin my boy’s future. He has his heart set on playing major-league baseball. — F.C.

ANSWER: The age to throw a curveball is a topic fraught with contradictory statements. For many years, experts taught that 14 was the youngest age to allow pitchers to throw curves. The reason given was that the immature arm cannot tolerate the stress on the elbow and its ligaments required to throw a curve. That teaching was not supported by strong evidence. Only anecdotal evidence was given.

New studies repudiate that point of view. The University of North Carolina conducted a study on youngsters between the ages of 8 years through college age and found that throwing a curveball was no more harmful to a young pitcher’s arm than throwing a fastball. The study showed that the more important contributor to injury is the total number of pitches thrown in one session.

If you want to save your boy’s arm, you or he have to keep track of the number of throws he makes in one day. Little League regulations say that 7- and 8-year-olds ought not to throw more than 50 pitches in one day; 9- and 10-year-olds, 75 pitches; 11- and 12-year-olds, 85 pitches; and 13- to 16-year-olds, 95. A pitcher who throws more than 66 pitches in a game should have four days of rest before pitching again; 51 to 66 pitches, three rest days; 36 to 50, two rest days; and 21 to 35, one rest day. Practice throwing should follow the same rules.

I can’t give you a precise number for the safety of throwing curveballs. Young pitchers should use a variety of pitches, and not overdo the curve.

DEAR DR. DONOHUE: I am a 65-year-old man who rides a recumbent exercise bike every day. I ride for one hour, nonstop, at 20 miles per hour.

I am getting good results in weight loss and lowered blood pressure. I wonder if my intensity and frequency of bike riding is doing any damage to my testicles or prostate gland. The seat is moderately padded. — F.H.

ANSWER: Bikers who sit on a hard seat for hours and hours put great pressure on nerves to the penis. That can lead to erectile dysfunction. Most often, warning signs are present. The biker feels numbness in the genital area.

You are in a recumbent position. You are not putting too much pressure on pelvic nerves. You don’t run a risk of erectile dysfunction. You also are not doing any damage to the testicles or prostate gland.

DEAR DR. DONOHUE: In three weeks I’ll be 80. I am in good health. I have one minor problem: I find it difficult to stand up after sitting on our couch. The seat isn’t as far off the floor as our chair seats are. I think I have weak thigh muscles. I used to do squats in high school. Should I resume them now? — M.G.

ANSWER: Let me give you a modified squat that will be easier on your knees. Put two pillows on a steady chair, one whose seat is higher than the couch’s. Stand in front of the chair with arms crossed over each other on your chest.

Lean a little forward and then lower yourself onto the pillows. Do as many repetitions as you can do comfortably. Try to increase the number of reps as the weeks go by.

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.