When taking part in an Ultramarathon in the extreme conditions that the Yukon Arctic Ultra presents, its essential that competitors are equipped with the highest quality gear and clothing. Proper extreme cold clothing is all about proper layering, and proper layering starts with the next-to-skin base layers that must achieve a few main objectives: Offer warmth for the body while wicking any sweat away from the body all while staying as dry as possible. Failure to accomplish any one of these goals will leave a competitor with being unable to regulate core body temperature and risk cold injuries such as frostbite, exhaustion or hypothermia, especially when temperatures plummet to -40 degrees Celsius. And this is exactly what I faced this year at the 2020 edition of the 100 Mile Yukon Arctic Ultramarathon. We faced temperatures as cold as -40C during the night, however during the afternoon we were greeted with milder than normal temperatures of about -12C. This is a difficult temperature range to stay warm but also avoid sweating when pulling a 70-pound pack while slow running or fast hiking through the Yukon wilderness. Luckily I had brought both the Extreme Wool and line of Brubeck base layers for colder weather and the Active Wool line for the less extreme cold, which is the layer I used throughout the race as it not only felt great as a next to skin layer, but it did its job of keeping me warm, while wicking any sweat away from my skin instantly. And what amazed me the most was its ability to stay dry throughout the race. Because this race is so remote and potentially dangerous, it was imperative that I paid close attention and constantly checked my base layers to feel for moisture, because when those temperatures drop, it’s a dangerous scenario to have wet clothes against your skin. These upper and lower body base layers did the perfect job and with the confidence I had in my layering, I was able to focus on my performance and throughout the race and truly enjoy the Yukon experience. Dr. Chad Barber