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For most of you, the dangerous heat we discussed in August has given way to its only comparable weather threat -- cold. Cold kills about as many people as does heat, and probably kills off more exercise programs than heat does. It's time we took a look at the cold and its effects on our health, exercise, and fun.
Fun? In the same sentence with c-c-cold? Darn right ... just ask any skier, boarder, ice skater, snowmobiler, hockey player, ice fisherman, Green Bay Packer, or anyone who simply enjoys winter. The only weather that counts is the weather next to our skin, and the right clothes can control that. That's a bonus winter offers that summer doesn't. There's no reason to "gut out" or even avoid the cold when we can make it go away by dressing properly, whether we're walking to work or running a 10k.
Chilly environments, especially combined with advanced age, a macho attitude, or alcohol, kill several hundred people in the U.S. and over 26,000 in London each year. Anyone spending any time in cool or cold surroundings, whether playing or working outdoors or watching TV in a poorly heated home, is at risk and should dress to stay comfortable. That's our front line weapon against cold and its primary threat, hypothermia. When a body can't produce heat as fast as it loses it, hypothermia follows, starting with simple shivering. Any temperature below skin temperature saps energy from even a young athlete's body, and little old ladies can die of hypothermia on a pleasant day.
Air temperature is the foremost consideration, but wind, humidity, and shade also significantly impact the rate of net heat loss. Wind makes a huge difference as it sweeps away air warmed by our skin; thus the wind chill chart (see http://188.8.131.52/er/iln/tables.htm for the new one), which quantifies how rapidly our bodies cool down to the ambient temperature. Low humidity increases evaporative cooling, and high humidity or rain increases conductive cooling. Bright sunshine can raise the effective temperature by up to 20 degrees, so sudden shade or cloud cover can very noticeably drop apparent temps
The greatest risk of hypothermia occurs in cool (40°-50° F), wet weather (does that sound like wintertime London?), especially when the individual is fatigued. Athletes are usually at low risk for hypothermia because their exercise generates plenty of heat, but having to stop away from shelter due to fatigue or injury dramatically increases their risk.
Moisture from rain, snow, or sweat can greatly increase heat loss. Rain's effect on an active athlete is minimal above 50 degrees, but increases dramatically as temps drop into the 40s and 30s. Sweat becomes a problem primarily when the athlete slows down, or has soaked his clothing because he wore too much or the wrong type. Every skier knows how cold it can get sitting still on a breezy lift while sweaty from his last downhill run, and that's why the experienced ones wear thin layers rather than one big coat.
Layers trap heat between them and allow us to vary our insulation to control our comfort real time. The first layer must wick sweat away from your body, and works best if it fits snugly. Cotton is poor, polypropylene knit is very good, and high-tech wicking fabrics are the best. The next layer is insulation, and it must insulate when wet. Wool is good; higher-tech materials such as high-quality synthetic fleeces are warmer, lighter, and washable. Fabrics that breathe air, let water vapor exit, and keep liquid water out, such as Gore-Tex, are the best outer layer in windy or wet weather. Nylon does not breathe and may increase perspiration and lead to wetter clothes. Zippers in the outer layers greatly help versatility. An open, uncoated fleece outer layer in calm, clear weather will let air flow through in proportion to your exertion level in self-propelled sports, helping to regulate your temperature automatically as you run, skate, bicycle, or ski. A knit cap and gloves or (better) mittens are vital to comfort and safety in lengthy exposure or serious cold.
Dress for how you are going to feel after you're warmed up. Each individual must learn through experimentation how much and what types of clothing s/he needs to stay comfortable, as individual needs vary by huge amounts. A big factor in staying comfortable in brief exposure to cold weather, such as walking from car to office, is mental, as our bodies won't lose any significant amounts of heat in ordinary cold weather in a few minutes. A single big, thick coat is fine for that purpose, but not for exertion in the cold.
If precautions fail and hypothermia disables someone, the victim must be immediately warmed by moderate external heat. It is life-threatening, so desperate measures may be needed. The simple screening test for hypothermia is the "umbles" test: stumbles, mumbles, fumbles, and grumbles which show changes in motor coordination and levels of consciousness. For an extensive, clear, practical, and interesting discussion of hypothermia, click on http://www.princeton.edu/~oa/safety/hypocold.shtml.
Two more health risks emerge in cold weather. Frostbite -- frozen skin or flesh - requires freezing temperatures, is greatly exacerbated by wind (which explains its inclusion in the wind chill charts), and usually starts with fingers, ears, and nose ... as long as the athlete keeps moving. The feet are at risk primarily when a person is disabled and stranded in frigid weather. Frostbite has serious consequences, and should be prevented even if that requires exercising indoors. If it occurs, apply mild heat from warm water or someone else's body heat. Nothing more than hot tub temps (105 degrees), though; warmer water or rubbing are dangerous, and applying snow or ice is downright stupid.
Another common cold-weather injury is muscle, joint, or ligament damage, usually impact trauma and muscle pulls from slipping, muscle guarding (tensing to avoid falls), and cool muscles. Prevention is obvious: warm up thoroughly before exertion, don't stretch cold muscles, don't run on ice, and take shorter steps on slippery surfaces. One injury could offset the whole season's running benefits. Cold-weather conditioning does help our bodies and minds adapt to the cold, though, if preparing for competition in cold weather or for cold-weather sports.
No, your lungs are not going to freeze, not even in arctic weather.
Alcohol, caffeine, altitude, barbiturates, nicotine, narcotics and tricyclic antidepressants all compound the effects of cold, and extra food and water before heading out help us combat the cold. Warm, sweet, non-caffeinated drinks are preferable. If your urine is not pale and clear, or if you're thirsty, you're dehydrated. If you're dehydrated, your mental and physical performance diminish measurably, your joints suffer, you get colder, frostbite is more likely, and headache may occur.
When jogging or cross-country skiing on a breezy day, run into the wind on the way out and with it on the way back, when you'll be more tired and sweaty. In really nasty weather, walk or run more, shorter laps, so if you do get cold or injured you can stop and get warm quickly. Ideally, you may want to warm up and cool down indoors if possible. Just imagine the extra comfort and safety factors that provides! Take it a step further: take your walk in a commercial or high school gym or in a mall. If your whole winter is truly nasty and ice or snow sports don't interest you, consider some quality home gym equipment or join a gym just for the winter. It's well worth the expense if it keeps you exercising when the weather outside would discourage you. Or just switch from outdoor sports to indoor sports if they float your boat. There's nothing to be gained by being macho, and basketball is a great workout.
Be wary of post-exercise hypothermia. It can develop rapidly after exercise because heat production has ceased and heat loss due to sweat, wet clothing, skin blood vessel dilation, and increased circulation is still going full tilt. To avoid hypothermia when you stop, get covered up, get dry, get into a warm place, and replace fluids. Soldiers have died in their sleeping bags even in controlled training exercises because they went to bed in sweaty clothes.
Of course, you could just make like a slug all winter, but that discards a great deal of the conditioning you developed over the last nine months and costs you three months of fun you can never replace. No need for that, given the degree to which the right clothing can change the weather from cold to comfortable. Put on some warm weather, get outside, and have some fun!