Hi, I have a question I would really appreciate some thoughts on.
I do a lot of day treks here in Japan, often between 30~50Km, once or twice a week (I live close to a mountain range and can start close from my house).
I normally keep a pretty constant pace of between 5~6Km/hr, letting the uphill parts be part of my interval training, easing back into normal aerobic effort during the less steep and downhill sections.
This means I do sweat a lot, as I don’t slow down to prevent this from happening as it’s part of my ‘training’.
During the winter months this can be a bit of a problem.
During temperatures of 0~10˚C I wear a thin base layer from Montura (think Capiline 1 or 2 equivalent) with a pretty breathable wind layer (Rab Alpine Jacket) on top. When I’m active this is still too warm for me not to have my shirt wet out from perspiration. Wet and warm, what is the problem you would say. I find though that I get cold flashes and fever-like behaviour as if my body can’t decide if it’s cold or hot etc. This made me wonder if I shouldn’t wear a bit thicker base layer, even though I’m sweating. I tried and do have several thin grid fleeces (think Cap 4 hoody equivalent) that work well for me at much lower temperatures, but around freezing these are still too hot to really go hard climbing up. Initially the extra comfort the dry and warm thin grid fleeces is great but soon I overheat again. 

I do dump heat by unzipping and exposing my forearms, which helps a bit. I used to put on/off/on/off my wind shirt (Montbell Tachyon), but went to the more breathable Rab Alpine Jacket (and on other ocassions Rab Boreas), for less faff factor if you will.
This made me wonder what trail runners wear, and if they run into similar situations. If they just ignore the cold flashes and shakes like I’ve been doing up till now, or if they have a better system going for them. If you are a trail runner, or do similar high exertion activities, would love to hear what works for you.
Any thoughts or experiences you would be willing to share greatly appreciated.
(edited for clarification)

