By Michael Lanza
Staying warm while skiing or riding at resorts or in the backcountry, Nordic skiing, snowshoeing, hiking, or running in winter is a constant challenge: We sweat, our clothes get damp, and then we have periods of reduced exertion like riding a ski lift or walking or running downhill, when we cool down. But as humans have known for thousands of years, it’s a matter of smartly managing and insulating our body’s furnace (and today we have much better technical clothing than animal skins).