Richard L. Bruno is chairperson of the International Post-Polio Task Force and director of The Post-Polio Institute at Englewood Hospital and Medical Center. Please e-mail questions directly to him at ppseng@aol.com.

Note: This column is for information purposes only and is not intended as a substitute for professional medical advice.

Q: Why are my feet and lower legs always ice cold and purple, especially in winter? My doctor checked my blood flow and says it sounds "clear." I've tried heavy socks and leg warmers. What's going on? What can I do to stay warm?

You have "polio feet," feet and legs that are always cold and purplish. Your blood flow sounds "clear" because your arteries are open. It's your veins that are the problem because they are too "open."

Polio survivors have trouble with cold because the neurons in the brain and spinal cord that cause the veins to contract were killed by the poliovirus. You are unable to stop warm blood from pooling in the veins near the surface of the skin, causing the feet to look purple or even blue. As the outside temperature drops, pooling allows the loss of heat from warm blood near the surface of the skin and causes your tissues to cool. Motor nerves and muscles--lying just below the surface of the skin--cool. Cold motor nerves conduct more slowly and may be less able to make cold muscles contract quickly and forcefully. Tendons and ligaments also get cold and become less elastic--like putting a rubber band in the freezer--making movement of weak muscles more difficult. Cold causes muscle weakness in 62 percent of polio survivors, muscle pain in 60 percent, and fatigue in 39 percent. It takes hours under an electric blanket or a long, hot bath to warm cold legs and regain strength.

We found in our very first study of PPS that polio survivors lose 75 percent of their strength when the temperature drops from 85 to about 65 degrees. We also found that polio survivors' motor nerves function as if it's 20 degrees colder that the actual temperature. So, polio survivors should dress as if it's 20 degrees colder than it actually is. The trick is to stay warm from the get-go. You should dress right after showering when your skin is warm and reddish. Try heat-retaining sock liners or even long johns made of the woven, breathable plastic fiber polypropylene. Then put on warm socks or try battery-powered socks or ski-boot insoles. Also, keep your feet elevated as much as possible during the day.

Remember that changes in season are also difficult, since your body can't figure out whether it's warm or cool. Polio survivors report more muscle pain, especially headaches, during seasonal changes. Regardless of the season, whether you're being chilled by a northeast wind in November or by excessive air conditioning in August, dress in layers to control your body temperature, because your body can't.

Q: My legs are so cold that when I come home from work I fill the tub with warm water and soak my feet. Last night, when I stood up from the tub bench, the legs inside the tub collapsed. Are tub benches dangerous to use?

Tub benches are wonderful bathroom aids. Polio survivors who have weak arms and legs should not stand to shower, nor should they be hauling themselves in and out of the tub. A tub bench helps you to conserve energy and be safe in the tub, provided you are careful. Adjustable tub benches allow you to change the height of the seat by using "detente buttons," half-round pieces of metal that fit into holes that are drilled into the tub bench legs. The brand of tub bench you have uses a V-shaped spring-steel wire that forces the detente buttons into the holes to hold the legs at a given length. Every time you fill the tub with water, the steel wire becomes wet. Over time the wire may rust through, the detente button can fall out and the legs collapse. Any device that uses detente buttons to adjust the length of its legs--a tub bench or even crutches--should be examined frequently to see if the spring-steel wire is rusting or no longer holding the detente buttons in place.