Welcome back to CMH Heli-Skiing, Dr. Delia Roberts, and Arc’teryx three part article on Clothes for All Weather, or how to dress to stay warm and dry whatever the weather and changing conditions bring your way. In our last post on Clothing Choices to Keep you Skiing in All Weather we described some of the options available in the CMH shops for the base, or next-to-skin layer. This week, as the snow begins to accumulate up in our mountains, we’ll tell you about the Mid-layer; the one you can change around to increase or decrease the amount of insulation provided. You may find that you’ll want to own several weights of mid-layer clothing, one for those really cold days and another for warmer ones.
Issue: Cold environments rob our bodies of precious heat. Significant heat loss occurs when you’re exposed to cold air or come into direct contact with cold surfaces. The greater the temperature gradient between your warm body and the cold air/ground the greater the heat loss. The addition of moisture accelerates this process. As the base layer absorbs moisture from your skin it will quickly become soaked unless the mid-layer can pull the moisture away and pass it onward and outward.
Solution: Mid layers are designed to capture warm air and hold it around your body. In order to be most effective midlayers should also continue transporting moisture away. Insulating fibers like polyester and wool retain the warmth generated by your body because the structure of the fibers creates small air spaces that trap molecules of warm air.
CMH Choice: Wool and synthetics are well suited to retaining the warmth generated by your body. In mountain environments synthetics have the added advantage of being quick drying and maintaining their thermal properties when wet. Modern synthetic fleeces come in many different weights and can range from a slim fitting next to skin base layer through to large heavily insulating jackets. The beauty of layering is that you can choose the right level of insulation for your needs. Mid layer garments can also be layered on top of each other to build additional warmth for those extra cold days. It is best not to have too many layers though, as this can become restrictive.
Additional features, such as arm-pit zippers and full-length front zippers, allow venting to cool you off when you are working hard or the sun comes out, and to circulate air and help get rid of the moisture coming out of your base layer.
Arc'teryx Recommendations: Arc’teryx offers two different mid-layer weights.
For warmer days the Covert series features a polyester sweater knit fleece. Its high loft and high air permeability make it an excellent mid-layer and when combined with an outer shell it traps large amounts of air to achieve great thermal efficiency. When you open your vents the open structure allows the air to circulate for temperature adjustment and removal of moisture.
On colder days Arc’teryx suggests the Atom LT. This jacket features polyester fiberfill insulation under a snow shedding stretch woven face fabric. Breathable fleece panels through the side of the jacket allow it to work well in a layering system while wind and water resistant surface mean the jacket alone can replace the mid- and outer- layers on warm days.
What have you found to be the ultimate mid-layer while out skiing? Tell us here in the comments!
About the author: Dr. Roberts is an Exercise Physiologist who has worked with Olympic medalists, Heli-Ski Guides and is currently working on injury prevention for Ski Patrols and Ski and Snowboard Instructors. Send us your training and physiology, diet and performance oriented questions or contact Dr. Delia Roberts at firstname.lastname@example.org