by Brenda Braaten | 2001-06-25 03:00:00-06
As I stood in the frigid cold stomping my feet in the snow, watching my husband hastily putting up the tent in the fading light, I admitted defeat. Three separate attempts on Mt. Whiteface (a relatively insignificant 4,000-footer in the White Mountains) and three times defeated by weather. Leaving home, we had optimistically calculated a same-day return. Before we had traveled a mile up the trail, however, we realized that it was a good thing we had packed food and gear for two days. Snow that had just been dusting the lowlands quickly turned to snowdrifts as we ascended. We were soon post-holing up to our knees, castigating ourselves for leaving our snowshoes in the warmth of our basement one hundred miles away. Following in the footsteps of my husband, I had it fairly easy, but by 4 pm I was exhausted and grateful to see the sun setting, knowing that fading light would be the catalyst for setting up camp for the night. Our destination nowhere in sight, we had to rethink the itinerary.
The tent ready, my husband turned eagerly and asked where I wanted to set up the kitchen. I snapped back: "No Food! I'm too cold. I can't eat." as I dove into the tent and the insulating layers of sleeping bag and liner. Concerned for my well-being (and perhaps a bit hungry himself), he soon had the stove humming and fixed dinner as I dozed off. "Here, drink this, you're dehydrated," he admonished as he handed hot soup into the tent. It hurts to say it, but he was absolutely right. I hadn't reckoned how quickly the extreme hiking effort (ascending and post-holing) and the dry cold air would sap the moisture from my pores and from my breath. I had not replenished my losses, repeatedly rejecting his offers of a sip from his water bottle. The dehydration had turned to nausea at the thought of dinner. It was not the cold that was defeating me-it was my own stupidity. What had I learned from this day's journey?
First, recognize that when hiking in extreme cold (below 10*F), you will be burning an additional 250-500 Calories/day (see Endnote 1). Your body will be running the furnace at full blast to keep your core temperature within reasonable limits, but the layers you are wearing should protect you from using excessive Calories to keep warm. The real Calorie burner is the extra effort it takes to move more gear over worse terrain. Even relatively level terrain is more challenging if you are post-holing into knee-deep snow at every step. It takes twice as many Calories to walk in soft packed snow as it does to walk the same distance on cleared trails (Askew et al., 1989).
Getting more fuel when weather is extremely cold becomes a challenge, since slowing down for a three course lunch means a drop in body temperature with resulting cold fingers and toes. Thus, "grazing" should be the meal pattern: small, frequent snacks throughout the day to most effectively fuel your muscles. To adapt your normal warm weather menu, plan to add 4-8 extra servings of high carbohydrate/high fat snacks per day, with lunch reduced to the status of a "large snack". Plan to nibble along the trail, as hands and feet will freeze up quickly if you stop for a mac 'n cheese delay.
Put on extra layers before you need them, as soon as you slow down, to avoid long moments of uncomfortably cold extremities later on. To avoid robbing your arms and legs of necessary circulation, eat small meals, rather than large meals that shunt blood to the intestine. Timing your meals will also make a difference in how you feel. Eating dinner or a hearty snack just before you go to sleep (500-1200 Calories) will help you sleep warmer and more soundly.
Editor's Comment: One of our reviewers adds, and Dr. Braaten agrees, that "…these calories should include a high proportion of fats, which can be utilized more efficiently, and a significant portion of protein, needed to restore muscular endurance for the following days' activities, should be included in that amount."
Stay Hydrated. Dehydration compounds the effects of cold weather exertion, causing more physical strain on heart and skeletal muscles, leading to earlier exhaustion. Avoid dehydration by sipping water often throughout the day. To keep water bottles from freezing, pack them inside your jacket next to your body, sleep with them in your sleeping bag (along with your boots--in a plastic bag of course), and buy/make an insulated bottle jacket. Two partially full bottles will freeze faster than one full bottle, so combine the water bottles if you have two that are less than half full. Adding gatorade/Kool-Aid will depress the freezing point, keeping it liquid longer, but at less than 10*F even sugar water will freeze. Fluids that contain too much sugar will promote diuresis (you lose more water than you gain), so a 7% solution, or approximately 1/3 C powder per liter, is recommended to maintain optimum hydration status (Rintamaki et al., 1995).
Avoid any food that makes you "think you're hot when you're not". Foods that cause you to break out in a sweat--alcohol or spicy foods containing hot peppers, for example. Even too much hot fluid at once can cause vasodilation, allowing precious warmth to escape from your pores. Water/fluid should be about body temperature, or taken in small sips if very hot (Rintamaki et al., 1995). Avoid high protein snacks, as they increase your water requirement and reduce your cold tolerance. Ten to 15% Calories from protein is generally adequate (Stroud et al., 1996).
Be mindful of the effect subzero temperature will have on your food rations. What are you going to do with 5 bagels that have frozen solid on your high country/mid-winter trip? Use them for hockey pucks? Take chips or cheese crackers instead. Generally, the less water in any food, the better. The lower water content makes them less likely to freeze solid. Pack dehydrated soup and instant cereal mixes, Summit bars or granola bars--foods that require little or no preparation and that contain no water. (See www.frc.mass.edu/bbraate/packlite/index.htm for Water Content of Common Trail Foods; Ed. Note 9/12/04: Dead link) Do as much of the food preparation as possible in the warmth of your kitchen: slice sausage/Kielbasa and cheese, package food in baggies so that all you have to do is heat water to a boil and dump the contents in. No stirring required; no frozen fingers. I even remove tea bags from their wrapper. Think through every step of food preparation that will be required on the trail as though you had to do it with mittens on, and simplify accordingly.
Beside needing more fuel yourself, you'll need at least 3 times more stove fuel to melt snow and heat it to boiling (not correcting for additional environmental losses due to conductance, exposure to wind, etc.). Everything will take longer--take plenty of fuel (see Endnote 2).
When melting snow, be aware that you should start with some liquid water in your kettle, otherwise your pan will scorch and the water will taste burned. (Editor's Note: some water in the kettle will also improve the heat transfer efficiency among the water phases in the pot and promote faster melting time).
Because there were teenagers awaiting our attention at home, we returned to the valley the next morning. We had not conquered Mt. Whiteface this trip, but it was not the cold that defeated us. Rather, because the cold had discouraged the masses, we had been graciously provided with what we needed most: profound solitude, spirit-renewing perspective. Undaunted, we could eagerly anticipate "the next time", better educated than when we began this trip. Next time, I'll bring the snowshoes, and yes, I'll drink my water throughout the day.
1. Editor's Comment: One of our reviewers wrote: "Dr. Braaten claims that you will burn an additional 250-500 calories per day at cold temps. This seems low, indicating an amount of increase due to the basal metabolism (thermoregulation) functions alone, and may not consider the additional extreme physical exertion normally encountered under winter conditions." We gave Dr. Braaten the opportunity to respond, and she replied: "Most folks will dress adequately for cold conditions, so increased BMR is unlikely/insignificant. I agree, cutting new trail through three foot snow drifts would increase caloric needs substantially…However, I suspect that most of us will be following a blazed trail, or only occasionally putting out that kind of effort. Add to that shorter days (less daylight), and calories may come out about the same as they would under "friendlier" conditions."
2. We're obsessive about mimimal fuel on longer treks in moderate weather, (see our website) but quite liberal when camped in subzero temperatures. Aside from more fuel required to heat water for cooking, we drink more hot fluids, and melt snow. Better to err on the side of safety. - BB
Askew, Eldon W. Nutrition for a cold environment. Phys and Sportsmed. 1989, 17(12).
Rintamaki, H., T. Makinen, J. Oksa and J Latvala. Water balance and physical performance in cold. Arctic Med Res 1995, 54 Suppl 2:32-6.
Stroud,MA, AA Jackson and JC Waterlow. Protein turnover rates of two human subjects during an unassisted crossing of Antarctica. Br J Nutr. 1996, 76(2):165-74.
"Nutritional Considerations for Cold Weather Hiking," by Brenda Braaten. BackpackingLight.com (ISSN 1537-0364).
http://backpackinglight.com/cgi-bin/backpackinglight/00040.html, 2001-06-25 03:00:00-06.