DEAR DR. DONOHUE: I consider my husband a fanatic. He runs five or more miles almost every day. He is skinny as a rail. Is he setting himself up for arthritis by such a grueling schedule? – D.K.

ANSWER: Exercise is not considered a factor in causing osteoarthritis (or rheumatoid arthritis). However, if exercise is painful, there’s something wrong with the joint, and it shouldn’t be used until the cause of the pain is found. Exercising an injured joint does damage it.

There’s a possibility that exercise might prevent osteoarthritis. That statement, however, awaits more proof.

Osteoarthritis is the common kind of arthritis, the kind that comes with age.

DEAR DR. DONOHUE: I use a pedometer for walking, but I don’t understand how steps are converted into the number of miles walked. Please explain. – O.K.

DEAR DR. DONOHUE: Maybe I’m making things too complicated, but I have taken up walking as my exercise, and I wonder if there is a proper way to walk, one that gives the most benefits. Is there? – P.M.

ANSWER: I’ll combine your questions in one answer.

Walking is more than putting one foot in front of the other, but it needn’t be turned into an engineering task.

The proper walking posture is one with the ears centered over the shoulders and the shoulders centered over the hips. Leaning forward makes a person unstable, as it moves the body’s center of gravity out of line.

The heel should strike the ground first in a walking step, not the front of the foot.

Arms are allowed to swing naturally without the hands crossing the center of the body. Many experts tell walkers to bend the elbows 90 degrees. If that’s comfortable for you, go with it.

Pedometers are small gadgets that hook onto a belt. They count steps. Two thousand steps is 1 mile. That’s an estimate, since stride length and step frequency need to be factored into a precise estimate of distance, but it’s close enough for most of us. Strive for a total of 10,000 steps a day — five miles. You don’t start at that number. You work your way to it slowly. And you don’t have to take 10,000 steps in one session. You can break your walks into two or three different periods.

As for the pace of walking, it should be one that the walker considers “moderate.” People can make that determination for themselves. If you want a guideline, a low pace is 80 or fewer steps a minute, and a brisk pace is 100 or more steps a minute.

DEAR DR. DONOHUE: I’m a musician and a runner. I play tuba and run about two miles every two days, but I’ve experienced some breathing problems recently. For instance, I could run a mile and play tuba afterward without my chest hurting, but now it starts to hurt if I run before I play the tuba. I have had my chest checked, and nothing was found. Is the problem that my lungs are not able to expand as much? – M.W.

ANSWER: I don’t think so. Running increases lung volume.

I need to know more about the pain. Does your chest hurt when you twist? If so, the pain could be chest muscle pain. I can’t blame that on running either.

I also need to know your age and your smoking history. Would you write me again with some more information?

DEAR DR. DONOHUE: My 40-year-old son has ichthyosis. He was diagnosed as having the X-linked kind. As an adult, someone changed the diagnosis to ichthyosis vulgaris. What’s the difference? Only the men in my family have had it. Since the condition is passed from mother to son, does this mean it stops with my son? – R.L.

ANSWER: Ichthyosis (from the Greek word for fish) is a skin disorder where scales, like fish scales, are on the skin. It has a number of variants. Ichthyosis vulgaris starts between the third and 12th month of life. The scales look like they are pasted to the skin. It’s a dominantly inherited disease that an affected parent can transmit to sons or daughters, so this variety would not end with your son. Scaling diminishes with age.

X-linked ichthyosis usually begins before 3 months of age, and its scales are large and dark. On the neck, they make a person look like the neck is in need of washing. It is transmitted to sons by a mother who carries the gene but doesn’t have any signs of the illness. If your son has daughters, they could be carriers of the gene. Neither they nor his sons will have the ailment.

The Foundation for Ichthyosis &Related Skin Types is a storehouse of information on this condition. You can find it on the Internet at www.scalyskin.org.

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.