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CHILL FACTOR
by Douglas Chasar
It's before sunrise on a clear November morning in Phoenix. The weather on the news says the daytime high will reach into the upper 80's and may even break 90, normal for this time of year. With such a beautiful day in store, Wendy and I decide to spend the day in the saddle. Our destination: The Grand Canyon.

Two hundred seventeen miles away, climbing over 6348 feet and we'll find ourselves peering into the mother of all canyons, the namesake of the state of Arizona. We dress for cold weather despite the relative warmth in town. Additionally we pack all the extra clothing we can fit into my saddlebags. Wearing every stitch, we both look like leather-clad marshmallows.

The chill in the air descends on us as we make the initial 2500-foot climb. The road streaks past and the elevation inches higher and higher. The temperature creeps lower and lower. Our only salvation from the constant chilling wind is the climbing sun, which is now being obscured by a layer of thin clouds high in the atmosphere.

Though I'm wearing heavy winter gloves thick with insulation, my hands begin to tingle. The tingling begins to feel like icy pricks from the needles of a frozen cactus. Just over 50 miles from Flagstaff at 6910 feet, my hands become numb. Simply wearing heavy gloves makes working my bike's controls clumsy, but with numb fingers it's virtually impossible. I can't actually feel the pressure I'm exerting on the clutch and brake levers, so all I have is hope that skill and practice are enough to safely control my ride.

I'm wearing a wetsuit under my clothes, which has worked well in the past. The seamless front makes a great barrier to the wind. The rubbery neoprene/nylon blend holds in a good amount of heat like a whale's blubbery hide. While my hands are all but non-existent as far as I can tell, my torso is quite snug and toasty. The cold wind has a mind of its own. In time, its crystalline fingers lace their way down my back threading their way into the zipper down the center of my spine. It's now that I realize I'm more than toasty, I'm actually hot! The shirt I am wearing under my wetsuit is soaked with sweat. The skin on my arms and back pebble, and a shiver rattles its way from the depth of my bones.

We finally reach Flagstaff, and I am unaware my face is numb until I try to talk. We walk into a diner to warm up. I don't realize the cold has slowed my cognitive function until I try to order coffee for me and my wife. I'm looking directly at the color coded orange spout sitting warmly next to it's more innocuous green spouted counterpart, decaf, but the word momentarily escapes me. I'd like to order in a polite manner, but only a simple noun muddles its way from my sluggish vocabulary. Coffee.

I wrap both hands around the steaming cup and lift the liquid warmth to my face. The first few sips take a moment to reach my stomach where they begin to warm me from the inside. My cup is empty in no time and I ask for a second, restraining myself from insisting the waitress simply leave the pot where I can reach it. Wendy and I decide to order food, and the hot meal sinks in rekindling our inner warmth.

I strip my wetsuit down to the waist to allow my under shirt to dry as we eat. After an hour at the diner, we hit the road. Our full bellies and the sun, which has broken through the clouds, keep us warm as we continue our journey.

Relating this story to a co-worker the following week, I'm given an index of wind chill temperatures. The temperature in Flagstaff that day was 37 degrees Fahrenheit. At 70mph, according to the table, the air feels like it's only five degrees above zero.

Chill Factor

I have since lost the chart, but an official table of wind chill values and a calculator is available at the web site of the National Weather Service (NWS), a department of the National Oceanic and Atmospheric Administration (NOAA), (http://www.nws.noaa.gov). The calculator uses an older formula as well as a new formula to figure wind chill values. While the new formula is designed to "use wind speed calculated at the average height of the human body...be based on a human face model...and incorporate modern heat transfer theory," punching in numbers of my own, I find what I believe are inconsistencies. For example, numbers typical of my riding, 90 degrees and 65mph, produce surprising results: The old formula produces wind chill value of 89 degrees and the new formula comes up with 97 degrees.

I don't find the result of the old formula difficult to believe, but the new formula's wind chill value of seven degrees higher than the air temperature has me puzzled. I use some other variables and find both formulas incorporate the same inconsistency where wind chill actually becomes a heating factor. The threshold for the old formula is 90 degrees and the new formula's threshold is 80 degrees. According to the NWS, the wind chill formula will undergo another revision this year. Perhaps the next formula will be more accurate.

Too Cool

In addition to my surprise at learning I had been riding in nearly sub-arctic temperatures, my current research indicates I was suffering from hypothermia, a condition produced when the body's core temperature drops below 95 degrees Fahrenheit. Symptoms of mild hypothermia include shivering, blue extremities, blotchy skin, numbness and tingling while decreased coordination, muscle rigidity, slow breathing, and a slow or irregular pulse are symptoms in severe cases. Dr. Scott H Plantz, of the Department of Emergency Medicine at Mount Sinai School of Medicine describes, "As tissues cool, their cells don't work properly: The brain and nerves work more slowly, muscles contract with more difficulty and may cramp more easily, and the heart becomes prone to irregular beats." (Sessler DI: Complications and treatment of mild hypothermia. Anesthesiology 2001 Aug; 95(2): 531-43[Medline]) The extremities, arms and legs, can become 20-30 degrees colder than the torso as the body diverts warm blood into the core as the core temperature drops.

During severe cases of hypothermia, riders can lose consciousness and are more likely to ride over the edge of a mountain, into a ditch, tree or oncoming traffic, before freezing to death. Loss of the shivering reflex signifies the onset of severe hypothermia and is a sure indicator that it's time to get off the bike and find some warmth.

In addition to environmental conditions such as air temperature and altitude, the circumstances in which hypothermia will occur depend on an individual's physical condition. For example, very thin and elderly individuals are more susceptible to hypothermia as are those suffering from medical conditions of poor circulation (such as diabetes, heart disease, anemia and sickle cell disease). Malnutrition and dehydration are also risk factors associated with hypothermia, which does not require temperatures below freezing and can occur at moderate temperatures given the right conditions.

Riders exposed to cold climates for any period of time are prone to frostnip and frostbite as well as hypothermia. Frostnip is a condition characterized by numbness and tingling as the extremities drop below 59 degrees Fahrenheit and blood vessels narrow. Frostbite occurs when the tissue temperature drops below freezing level, and unlike frostnip, causes damage when ice crystals form in the tissue destroying the cells. According to the NWS, exposed skin can become frostbitten in 15 minutes or less at wind chill values -18 degrees or lower.

I find it unlikely I'll encounter temperatures at this extreme in Arizona. However, many northern states and Canada can see temperatures this low even during summer months. Hypothermia is a serious concern and in extreme cases can be fatal, though taking certain precautions will prevent riders from literally becoming chilled to the bone. Many variables contribute to the onset of hypothermia, but according to one source "a well-prepared traveler may be able to experience -40 or greater for extended periods with proper insulated clothing."

Ride safe, ride often...hell, just ride! - dpc



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