Since hypothermia is the most common cause of accidental death in the backcountry, proper clothing is essential to every backcountry user from novice to professional. Hypothermia results when the body loses more heat than it can generate. Effective dressing is the simplest way to avoid hypothermia in the diverse weather of the backcountry.
Effective dressing means more than simply owning the most expensive parka and the fanciest rain gear. World-class mountaineers have long known the value of specialized techniques in mountaineering dress.
At any time of the year, the most effective way to dress is by "layering". This method has been proven, not only on Mount Everest but in the cold northern regions of Minnesota as well. Layering simply means wearing one thin layer of clothing over another over another. Many experienced winter mountaineers do not carry a heavy down parka into the backcountry and for good reason. If they become warm underneath a down parka, removing the parka leaves them extremely exposed. Rather, they will carry numerous lightweight layers.
The advantage of layering is that one can add and remove protection from the elements in small increments, thus balancing heat generation with heat loss. In addition, layering traps dead air for additional weight-free insulation.
Composition of Layers
The body is a source of heat, which you want to retain within your clothing. It is also a source of moisture, in the form of perspiration that, in many situations, must be kept away from the skin due to the cooling effect of evaporation. For this reason, the layers of clothing near your body should be thin and porous to hold in heat and wick away perspiration. Middle layers should be thicker in insulating quality to hold in more heat, yet be able to dissipate the moisture further away from the body. Finally, the outer layers should be thick enough to prevent heat loss and still protect the inner layers from the external elements. The most effective outer layer is completely waterproof, yet allows water vapor (perspiration) to escape. Most conventional rain-gear does not allow water vapor to breathe, thus the body's perspiration is held within the layers of clothing, increasing evaporative heat loss and saturating clothes.
The key to mastering the layering system is to add or remove layers of clothing at just the right times. Remove a layer before you begin sweating; add a layer before you get cold. By doing so, you can balance the amount of your body's heat generation with heat loss. Conserve your sweat, not your water!
In discussing the "ten essentials," in previous posts we have suggested carrying additional clothes. This simple suggestion should not be overlooked, since a warm, balmy morning at the trailhead often ends in a cool, windy chill on the summit.
Be prepared, think before and stay safe!
For more information on backcountry safety, check out the Mountain Rescue Associations public education programs @ http://mra.org/training/public-education
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Mountain Rescue Association
Mountain Rescue Association