DEAR DR. DONOHUE: I love volleyball, but I am far from the best player on my team. I’d be a lot better if I could jump higher. What kind of exercise can make me a better jumper? I am a girl, if that makes any difference. – Anon.

ANSWER: Plyometrics makes people – boys and girls – better jumpers. There are many ways to perform plyometrics; I’ll give you two simple methods.

Get yourself a sturdy platform that’s 12 inches high. A box will do if it’s strong enough to support your body weight. Jump off the platform and land on your feet with your knees bent slightly. As soon as you land, jump as high as you can. In the first week, jump five times with a rest between jumps. Then you can start adding more jumps.

Find a place where your landing site has some give. Grass is a good place. If this exercise hurts your knees, discontinue it.

In a couple of weeks, increase the height of the platform by two inches and continue to do so until you reach 18 inches. You can go to 2 feet, but 18 inches is a safe height for your knees.

If you cannot get a platform, then you can perform plyometrics in a different way. Jump as high as you can and, while in the air, draw your knees to your chest. Land in the conventional way with knees slightly bent, and jump up again immediately upon touching ground.

DEAR DR. DONOHUE: Can a person with diabetes safely use a sauna?

ANSWER: If that person is sensible, he or she can use a sauna. Temperatures in a sauna can rise to 190 F, so no one should stay in one for hours and hours. If diabetics overheat their body, they might throw off their blood sugar. Since every diabetic should have a blood-sugar-checking device, it wouldn’t be a bad idea to check your blood sugar after coming out of the sauna.

Another issue is infection. It isn’t always possible to clean the sauna after each use. Sit on a towel in the sauna and, if possible, take a shower after getting out of it.

DEAR DR. DONOHUE: I am 26. I jog 3 miles every day. I also drink three glasses of low-fat milk every day. I have calcium deposits and wonder if the jogging and milk-drinking are contributing to them. Are they? – W.R.

ANSWER: Most calcium deposits are formed by the body as a defense. Places where there’s inflammation can be cooled down by depositing calcium. Calcium-rich foods are almost never implicated in such deposits. Exercise is another unlikely cause. However, if exercise causes bursitis or tendonitis, calcium can be laid down in those areas. That’s stretching matters. Where are your calcium deposits? I could be more definite about what I have said if I knew their location.

DEAR DR. DONOHUE: I got acne on my back while playing on the junior varsity football team. I don’t have acne on my face. How did I get it on my back, and how can I get rid of it? The season has been over for a couple of weeks. It freaks me out. – J.T.

ANSWER: Back acne is common among football players. The equipment and pads keep the back skin hot, moist and irritated – a perfect environment for acne. Next season, after every practice, clean your equipment thoroughly. Wear a T-shirt so that your pads don’t rest directly on your skin. The T-shirt, of course, has to be changed daily.

Don’t freak out. This thing also happens to truck drivers, who spend most of their day with their backs pressed against the driver’s seat. For your acne, get any product with benzoyl peroxide in it. It’s effective and relatively inexpensive. Use it according to directions. If it doesn’t work, let me know. I can suggest something else to try.

DEAR DR. DONOHUE: I was diagnosed in 1985 with transverse myelitis. Can you explain what this is? I stagger when I walk, so I must use crutches. I must have a catheter because I cannot control my urination. My entire left side is partially paralyzed. Any information you can give me about this will be greatly appreciated. – L.M.

ANSWER: “Myel” here refers to the spinal cord, and “itis” indicates inflammation. “Transverse” signifies that the spinal cord inflammation runs from the right side of the cord to the left side.

The spinal cord is only about the width of the little finger. It contains both nerve cables and nerve cells. The cables bring information to the brain and take directions from the brain to all body organs and muscles. Spinal cord nerve cells serve to direct muscle action in addition to the input that muscles get from the brain. Transverse myelitis interrupts the transmission of all these messages. Depending on what area of the spine the inflammation has settled – high in the neck or low in the back – signs and symptoms vary in their extent and severity. Common signs are back pain, leg weakness, loss of sensations and loss of urine control. Causes include viral infections, blood vessel blockages and illness such as lupus. There are many times when doctors cannot identify a cause, and the illness is then called idiopathic.

About one-third of transverse myelitis patients have a good recovery. Another third make a fair recovery. That leaves a third that don’t regain use of involved organs and muscles. In most instances, there is no medicine that promotes healing. However, things can be done for those who are left with incapacities.

There’s a field of medicine that gets far too little recognition. It is occupational medicine. Occupational therapists are highly trained individuals who can provide people with a variety of devices that make life more livable and easier. You can find these people in almost all hospitals. Contact one.