DEAR DR. DONOHUE: My basketball coach is gung-ho for stretching exercises. We spend at least 15 minutes of every practice doing all sorts of stretches. Some of us wonder what this is doing for us. Our coach claims that it keeps us from injuries. Does it? How? — J.D.

ANSWER: Some sports-medicine authorities are of the same mind as your coach. They claim that stretching lessens the chance of injury. The proof for that claim isn’t great. They also claim that stretching enhances performance. That’s another statement for which proof isn’t great.

Gymnasts, hurdle runners, dancers (it is a sport) and perhaps baseball pitchers might get an advantage from increased flexibility, but the average player doesn’t gain a whole lot. Stretching aficionados claim that stretching gives basketball players a greater span to reach for the ball. That sounds like a stretch to me.

Older, less-active people, on the other hand, do profit from stretching. With age and inactivity, flexibility is lost. Older people have a hard time bending over to tie shoes and trim toenails.

A safe way to stretch is to move the joint as far as possible without pain. When you reach that limit, hold the stretch for 20 to 30 seconds. Relax and repeat five to 10 more times. You will find that you’re able to stretch farther with daily exercises. Another good stretching exercise involves having a partner. The partner moves the relaxed arm or leg to the point where it’s on the threshold of pain. Then you contract the muscles briefly and relax. Your partner is able to move the limb a bit more.

Is it possible that you’re confusing warm-ups with stretching? The two are not the same. Warm-ups are things like calisthenics or slow running in place. They do warm-up cold muscles, decrease muscle stiffness, increase blood flow to muscles and increase the delivery of oxygen to the muscles. Warm-ups can improve performance.

DEAR DR. DONOHUE: During cold and rainy weather, I stand inside, lift both legs about waist high 200 times, five times daily (1,000 times in total). How close is this to walking at moderate speed 30 minutes daily? — G.R.

ANSWER: I don’t have a clear picture of what you’re doing. I take it you’re lifting one leg at a time and supporting yourself on the other, right?

That gives you a decent workout. You’re not propelling your body forward as you do when walking, but you are making demands on your leg muscles, and you are raising your heart rate.

You can determine for yourself how the leg-raising compares with walking. Take your pulse when you’re at the end of your walk and when you are at the end of your leg raises. If the pulse is approximately the same with each exercise, the two are close to each other in demands on your heart.

DEAR DR. DONOHUE: I am an active, 73-year-old man who bikes 30 miles a few times a week. I also swim on a regular basis. Recently I have had trouble breathing and am unable to finish my workouts.

I went to the doctor, who diagnosed me with right diaphragm paralysis. Can you tell me what causes this and what can be done to correct the problem? — J.R.

ANSWER: Paralysis of the right or left side of the diaphragm is not exactly an uncommon condition. On a chest X-ray, the paralyzed side of the diaphragm is higher than the other. The diaphragm is the chief breathing muscle. A glitch in the part of the brain responsible for diaphragm movement, a glitch in the spinal cord, inflammation of the nerve that serves one side or inflammation of the diaphragm muscle itself can lead to paralysis. For many people, a cause cannot be found. And for some of these people, function returns in months.

I’d see a lung doctor, a pulmonary specialist who can conduct breathing tests to see if there is another cause for your breathing troubles. They began recently and somewhat quickly. That makes me wonder if something else is going on.

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