Warning Signs During Cold-Weather Exercise

By Gabe Mirkin, M.D.

You feel cold most in your fingers, ears and toes. During World War II, gunners on the bombers complained bitterly about frozen hands, ears and toes. The Army Air Force added special insulation to their gloves, hats and boots, and the flyers stopped complaining, even though they still suffered frostbite on the skin of their necks and front of their chests. They had unzipped their jackets becausethey didn’t feel cold.

Following are tips to keep various body parts protected during cold weather exercise, followed by descriptions of (and warning signs for) hypothermia and frostbite.

Your Hands

To help keep your hands warm on very cold days, wear an inner layer of thin gloves made from loosely-woven material that permits sweat to pass through. Gloves allow you to control your fingers better than mittens when you shift gears or use ski poles. On cold days, you may also need a middle layer of a more tightly woven-thick material, and if it is very cold, an outer layer that does not let wind or water in. The single compartment of mittens retains heat better than gloves that have separate compartments for each finger.

If your hands feel cold while you are outside, swing your arms around rapidly from your shoulders with your elbows straight. This motion imitates a centrifuge that will drive blood toward your fingers and open up the blood vessels in your hands. You can also buy hand warmers to be used inside your gloves or mittens. They may be:

• iron that is air-activated, lasting for one to 10 hours and not re-useable
• crystallization types that can be reused (follow the package directions for reheating)
• electric types that can be cumbersome because they use a battery and wires

Your Ears

On days when temperatures drop below 50 degrees F (10 C), cover your ears with an earband or a balaclava that covers your head and neck and has a small opening for your eyes, nose and mouth. Cyclists and skiers can wear a balaclava comfortably underneath their helmets.

Your Toes

Avoid cotton socks because cotton holds water, while wool and various synthetic fibers do not. On very cold days, wear layers of socks and perhaps use knee socks. Cyclists, skaters and skiers may want to add windproof and waterproof booties that are designed to fit over their special footwear.

If cold feet still make you miserable, you can get the same types of warmer packets described in the section on hands (above), shaped to fit in your shoes or boots. When using them in cycling shoes, remember to place them on top of your toes, not underneath.

Body, Arms and Legs

Use layers of clothing because the air space between layers provides insulation from the cold. You generate a lot of heat when you exercise, so use full-length zippers on your outer layers so you can adjust to your changing needs by unzipping and allowing air flow when necessary. By wearing several layers, you have the option of removing layers or unzipping the front of a jacket.

The base layer should wick away sweat, so use fabrics made from wool blends, silk or synthetics. Again, cotton is a poor choice because it holds water. The middle layers should be breathable and provide insulation. The outer layer should be of a material that blocks wind and rain, so you can unzip it or remove it easily when you don’t need it.

Hypothermia

Hypothermia is a severe drop in body temperature. If you dress properly and exercise vigorously enough, it shouldn’t happen to you. Your body sends you signals as your temperature starts to drop. With a one-degree drop in body temperature, your speech can become slurred. This, in itself, is not dangerous, but it serves as a warning that you are losing more heat than your body is producing.

To protect yourself, you can produce more heat by exercising harder, or you can conserve heat by adding more layers of clothes or seeking shelter.

With a drop of three degrees, you will find it difficult to coordinate your fingers. Seek shelter immediately.

When your temperature drops five degrees, you won’t be able to walk and may fall and not be able to get up. Then you may not be able to get out of the cold and your body temperature will continue to drop rapidly and you can die.

If your clothes are wet, your temperature will drop even faster. Take the warning signals seriously. If you have slurred speech or difficulty using your hands, take immediate action or you may not get another chance.

Frostbite

Your normal skin temperature is a degree or two below your internal body temperature of 98.6 degrees F (37 C). When your internal body temperature starts to drop, your brain tries to preserve heat by sending a message to the nerves in your hands and feet to close the blood vessels there. With decreased blood flow, the skin temperature of your hands and feet drops rapidly.

When your skin temperature reaches 59 degrees Fahrenheit (15 C), your brain sends signals to open up blood vessels in your hands, causing your fingers to turn red, burn and itch. This is called the “Hunting Response” and is normal. You should get out of the cold immediately when your hands or feet turn red and start to itch and burn.

If you don’t get out of the cold, the blood vessels in your hands and feet will close down again and the temperature will continue to drop even more rapidly to below freezing. You will suffer frostbite and may lose your fingers and toes.

Raynaud’s Phenomenon

Some people have a condition called Raynaud’s phenomenon. Their hands turn white and hurt when they are exposed to temperatures below 60 degrees or placed in running water. The hands hurt and turn white because they do not have the normal “Hunting Response.” The blood vessels to their hands do not open as soon as their skin temperature in their hands drops to 59 degrees F and their hand temperature drops rapidly toward freezing.

If you suffer Raynaud’s phenomenon, try this treatment developed by Dr. Murray Hamlet at the Army’s Research Institute of Environmental Medicine. He had sufferers sit out in the cold with their hands immersed in warm water six times a day. This caused blood vessels in their hands to open while those elsewhere in the skin closed down. All people who were tested were able to be out in the cold without feeling pain in their hands after eight sessions done every other day.

The blood pressure drugs called calcium channel blockers, such as Nifidipine, can help to treat and prevent Raynaud’s phenomenon (Rheumatology, November 2005). Another option is nitroglycerin ointment that is used to treat angina. When applied to the forearm, it opens blood vessels leading to the hands. Check with your doctor to see if these prescription medications might be appropriate for you.

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Gabe Mirkin, M.D., is a sports medicine doctor and fitness guru. A practicing physician for more than 50 years and a radio talk show host for 25 years, Dr. Mirkin has run more than 40 marathons and is now a serious tandem bike rider with his wife, Diana. His website is http://drmirkin.com/. Click to read Gabe’s full bio.