A hiker climbs for hours with a pack on the back. The body heats up. Sweat forms under the jacket. If the base layer holds that sweat, the skin turns cold and clammy. The hike then feels long and grim. If the base layer moves moisture away, the skin stays dry and warm. That difference shapes the whole day.Seamless Thermal Underwear aims at this second path. YogasuitFactory, run by Jinhua...