Long underwear
Credit: Photograph by Levi Brown

For high-aerobic activities, you want a light pair that wicks enough to prevent evaporative cooling. For mid-aerobic activities, look for mid-weight fabrics with more insulation. [Icebreaker 200 Legging, $80, icebreaker.com (left); Patagonia Capilene 4 Expedition Weight, $79, patagonia.com (right)]