Clothing The best fabrics offer insulation from the cold and allow your body to shed heat and moisture. Loose-fitting garments also help prevent overheating and excessive perspiration, and permit freedom of movement. some fabrics offer less insulation when wet and require a separate waterproof layer. The layering principle The Core Layer The core layer of clothing, which lies next to the skin, should consist of a cotton vest or a long-sleeved, thermal top. This garment should be close-fitting, but not tight or constricting. It should be made of a material that will absorb perspiration and “wick” it away from the skin (transfer it to the outside material). This layer must be kept as clean as possible, to prevent a build-up of dirt that may clog up its pore and prevent wicking. The Second Layer The second layer should be loose-fitting, but with the potential for keeping the blood vessels of the neck and wrists protected and warm. It can consist of a zipped-up top with a polo-neck, or a shirt with a collar, sleeves that can be rolled up, and cuffs that can be buttoned. in hot weather, this layer may be the outside one, with perhaps just a windproof shell. a zipped polo-neck can be vented in warmer weather. The third layer The third layer should be a woollen pullover or light, fleecy jacket. If you are on the move, even in the a rctic, this layer is best removed to prevent you overheating. You can vent your insulated parka if you are still hot. when you stop to rest, you should replace the middle layer before you start to feel the cold. this layer can act as the outside one in mild, temperate weather, although you should keep a waterproof garment at hand. The outer layer The outer layer should be a jacket that is either wind-resistant or waterproof, or both, depending on the climate in which you are travelling. In the arctic, a padded, windproof parka is indispensable for protection against cutting winds. you must be able to vent the jacket, however, to avoid potentially dangerous overheating and excessive perspiration. In temperate areas, rain is the main problem, although you can wear a waterproof shell over the jacket.