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Layering and dressing for the extreme cold

Posted by Hamish on 25-Jan-2018 16:04:00

People have asked us how to dress for the extreme cold. Researching this blog post was interesting and we definitely learnt a few things about how to dress effectively for these conditions.

What happens to us in the extreme cold?

The human body is not designed for these colder temperatures, as most of us live in temperate and tropical climates . There are populations that have adapted to polar extremes - like the Inuit in Arctic Canada and tribes like the Nenets in the north of Russia - but the vast majority of us have no experience of living in sub-zero temperatures.

What happens when we get cold?

The human body has several defense mechanisms to try and boost our core temperature:

  • The body increases heat by 10-30w in the first minutes without any exercise. This may not sound like much, but it makes a difference.
  • Goosebumps: Our hairs rise and our flesh forms "goosebumps" - a kind of evolutionary echo from the times when our ancestors were covered in fur.
  • Shivering: Our muscles shiver and teeth chatter. This can increase our metabolism by as much as 4 times our resting rate! As you can imagine, you can only shiver for so long, as shivering burns a lot of energy, (glycogen) and the body only has so much stored. Stop shivering, and you are cold, you are in trouble, although you most probably will not know it, as you will be hypothermic.

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The hypothalamus, the gland in the brain that acts as your body's thermostat, stimulates these reactions to keep the body's vital organs warm. The hypothalamus's mission is to keep the core warm at all costs - sacrificing the extremities if need be. (Where the old saying of keeping the core warm comes from). When the core cools, the body sacrifices the fingers and toes first by constricting blood supply in the extremities.

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Armadillo Merino Champion, Bryn Huges, completing The North Pole Marathon

What happens when your core cools?

In one word - Hypothermia. Your core temperature only has to drop a few degrees before you can be in serious trouble and your body will start shutting down as it goes into the various stages of Hypothermia. You will lose dexterity and clarity of thought and it will be that much harder to complete even the most basic tasks. Hypothermia is a fast killer and has taken many lives and can happen to the best of us.

 

Now we understand a little about how the body reacts to the cold, how can we manage our comfort levels.

1. Try to avoid sweating

Easier said than done, as in the extreme cold the body will naturally generate heat (10to 30w) and moving through snow is hard work! This is why layering is essential. With this in mind, you want to stay at a "comfortable cold", you never want to get hot enough to start sweating! By staying at a "comfortable cold" you will not sweat and if you do it is minimal.

You must dress in layers and peel off those layers as your temperature increases so by layering you give yourself modularity to tailor your warmth up or down based upon your activity. The objective is to stay dry in these cold environments. By dressing in layers when you feel hot you take off an outer layer or even two, to allow your body to cool off, then when you feel cold again you throw a layer or two back on and you will warm up quickly. By constantly removing and adding layers when needed you will avoid sweating. You must stay dry! 

Also see our blog post - How to Layer - Tips on how to dress for your next outdoor adventure

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2. Dress in Layers

As highlighted above, layering is essential. When operating in the extreme cold your layering must be taken to a higher level:

  • Base Layer - the next-to-skin layer. The fibre/fabric needs to be able to move sweat off your skin efficiently. The fabric can be made of merino wool (which we recommend), or synthetic. A cotton t-shirt is NOT considered a suitable base layer and should never be worn in the outdoors because when cotton is wet the fibre pulls heat from your body and makes you feel cold. This is where the saying "cotton kills" comes from. 

 

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Hawk - Men's Long Sleeve 1/4 Zip Top
- 100% merino wool

Iona - Women's Long Sleeve 1/4 Zip Top
- 100% merino wool


  • Mid Layer 1 - provides insulation and helps to move sweat away from the baselayer.
    • Recommendation - add our soon to be released Lynx Lined 1/4 Zip or our Lion Lined 1/4 Zip HoodyThis is a mesh lined (90% merino wool mesh) top with a 100% merino wool outer fabric. The mesh efficiently moves moisture away from your baselayer and off the body and at the same time providing loft and warmth.

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  • Mid Layer 2 - provides insulation and traps air. Recommendation - add a light weight down or synthetic layer. 
  • Outer Layer - protects you from the external elements. This layer blocks the wind, rain, snow and everything else that gets thrown at you.

To learn more about the different Layers: 

Download Layering for the Outdoors paper

3. Think from core out.

Keep the core warm, and you will keep the extremities warm as well. The core should include the head, as we need to keep the brain warm for effective cognitive functioning. As the core cools, your hands and feet will feel it first as the body restricts the blood flow to these regions in an attempt to keep the essential organs warm.

"The more heat the body can conserve, the more successful the body is at keeping its core temperature in a healthy range" Ph.D Research Physiologist for the US Army Research Institute of Environmental Science John Castellani.

4. Resist the temptation to use a heavy baselayer

The temptation may be to use a heavy baselayer. In the extreme cold, if you are moving you will generate heat so a heavy base layer is more likely to make you sweat. The main challenges of dressing for the extreme cold is to not sweat at the same time as staying warm. Back to point 1, stay "comfortably cool". Layers are more effective in keeping you cool. If you use a heavy base layer, you remove the option of layering. You are better to use a lighter base layer and then layer up with a heavier insulative mid layer.

5. The "Wet - Dry" principle

This is a tip that we picked up from Roddy Riddle after his 350-mile race, the 6633 Arctic Ultra Run.

  • One baselayer set for day use
  • One baselayer set for evening tent and sleeping in

At the end of your day, take off the day set, and put on the "fresh" set for sleeping in or tent use. Dry the day use set in your sleeping bag over night, then wear it again the next day.

Two reasons to do this:

  • No matter how well you try not to sweat, you will generate some sweat (vapour or liquid), and the baselayer will become damp. By putting on a dry set at the end of the day, you will avoid any possibility of chills
  • You will feel better putting on the "fresh" baselayer, even if it is not fresh. There is something in the human psychology that likes to put on dry, fresh clothes and in an extreme environment the smallest lift can make a difference.


FullSizeRender-1.jpgRoddy Riddle during the 6633 Ultra

6. Manage Your Extremities

Properly insulated boots and heavy wool socks are key to maintaining warm feet. A heavy wool sock traps air between your foot and the inner boot lining to keep your feet warm. With this in mind, you may need to buy boots that are a ½ size larger than you would normally buy to allow for the heavier socks with a little toe wiggle room for added warmth. You want to avoid wedging your foot too tightly in a boot as this reduces the amount of warm insulating air.

Our recommendation: Heavy Boot Socks

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Layering up gloves allows you to manage heat better. Consider liner gloves, an insulation layer and an outer second wind proof layer. Another consideration is to use mittens vs. gloves when it is cold. Mittens allow the fingers to trap heat by being together.

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7. Should I drink alcohol?

In the extreme cold - NO. Some people living in freezing climates drink alcohol to warm themselves however this increases blood flow to the body extremities providing an initial feeling of warmth but this is only a temporary warming. Alcohol actually speeds up the loss of heat from the vital internal organs, resulting in a faster decrease in temperature while increasing the risk of a rapid death from hypothermia. Alcohol in the extreme cold is never recommended!

8. A few user tips:

  • Keep the inside of wrists warm. If you have problems with cold hands, buy liners and outer gloves that are longer and cover the lower 10cm of the wrist. By keeping this area warm, the hands will be warmer as the blood vessels are very close to the surface on the inside of the wrist.
  • Use a neck warmer to trap warm air that would otherwise escape up your back, then add a hat over the top.
  • Cover your face. Depending on your activity, you can use a long neck gaiter (Giraffe). This tip is from Roddy Riddle. The Giraffe may freeze solid due to the condensation from breathing freezing up. As it starts to freeze, swap it out with second one. Put the wet one down under your armpit to defrost it and then when it is defrosted and dried you rotate it with another frozen one.
  • In the cold, you will pee more, so make sure this is easy to do. Another useful tip from Roddy Riddle.

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Conclusion

The human body is not designed for the extreme cold, and we have developed technology and methods to enable us to explore and be active in all but the most extreme cold conditions. The key to surviving in this environment is to layer up and use the layers to manage your body temperature and be "comfortablely cool", as you want to try and avoid sweating.  

Sources:
https://www.ncbi.nlm.nih.gov/pmc/articles/PMC4861193/#!po=46.8750
http://www.bbc.com/future/story/20140107-what-extreme-cold-does-to-human
https://www.ncbi.nlm.nih.gov/pmc/articles/PMC4861193/#!po=46.8750
https://www2.palomar.edu/anthro/adapt/adapt_2.htm
https://www.theguardian.com/science/antarctica-live/2013/dec/05/keeping-warm-antarctic-peak-layering 

Topics: Outdoor, Bushcraft, Military, Search and Rescue

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