This question came in from Chris, in the middle of the last cold snap. With another cold spell upon us, it seemed particularly timely:
"What would you recommend for the ideal, close-to-skin-layer clothing for winter hiking and running. I've tried a broad range of all of the stay-dry, thermal stuff, but,no matter what, I wind up soaked and cold. A short hike on the day after Christmas, up Red Hill in Moultonboro, N.H., was not fun. On the way down, I was freezing. I would appreciate your ideas on clothing that truly keeps one warm upon exertion."
I wish there was some magic answer, some miracle base layer that would keep him warm and dry no matter what. But, if such a miracle garment exists, I've never found it.
The problem comes when you combine high-aerobic activity (climbing a mountain for example), with continued exposure to the cold, after you've gotten sweaty and stopped the real exertion.
The problem for Chris is not in his choice of base layer, but in what he expects it to accomplish. There's no base layer I know of that will keep you comfortable in cold weather, if you work so hard you get completely soaked in sweat, then stop exercising.
So, the real trick is to not get soaked in the first place, and that means -- you guessed it! -- dressing in layers and actively adjusting those layers to match your exertion level and the ambient temperature, so you sweat as little as possible.
Here's the drill:
n Make sure the layer next to your skin is as light as possible. Its only job is to allow moisture to move through rapidly.
n Start cold. Wear just enough layers that when you start, your fingers, ears and toes should feel noticeably cold. Not frost-bite cold, but not "comfortable" either.
n Once you are moving, start paying attention. If you warm up quickly, it's time to shed a layer, fast! You want to stay on the edge of "too cold" as long as possible. "Comfortable" is too warm.
n At some point, your body is fully warmed up and putting out maximum heat. For most of us, that's about 20 to 30 minutes after starting to exercise. Then, if you are still "too cold" add a light layer. But you'll be surprised at how often you end up wearing nothing more than your ultra-light base layer even when it's really cold.
n Wind chill can complicate things. Some of the new baselayers designed for cross-country ski racing and cold weather cycling have wind-proof panels in specific areas. But it's often easiest to throw on a breathable shell layer to protect from wind (and snow and snow falling from trees in the wind). Just make sure it's a shell -- no lining, no insulation.
n If you can't control your sweating, the only solution is to carry a change of clothes in a day pack. When you stop exercising, immediately take off your baselayer and don't put a new one on until you start to feel chilled. Only then. put on enough new, dry layers to keep you warm. If you put on a fresh shirt while you are still sweating, you've defeated the whole purpose.
I know it sounds odd, but, sometimes, you really do need to keep cool to stay warm.
Base layer choices
There are two schools of thought on base layers. One prefers fabrics that stretch and cling tightly to the body, arguing that these help draw the moisture off the skin more quickly. The other camp argues for looser fit, claiming the movement between skin and garment helps get rid of moisture. I'm firmly in the "clingy" camp, but urge you to experiment for yourself.
For active outdoor sports, nothing beats a quarter- or, better yet, half-zip long-sleeve T-neck. Pulling down that zipper lets you quickly vent a lot of heat and moisture, while zipping it up helps keep you warm when needed.
Then comes material. The real choices are synthetic polyester fabrics or merino wool. Both work -- if you keep cool and don't oversweat in them.
I use synthetics and wool almost interchangeably, but the more I use the new merino wool underwear (and socks), the more I like it -- with one exception. If you are really going all-out aerobically, the modern synthetics have a slight edge over wool at keeping you dry -- and warm.
Thermal regulation in action
I've climbed on two different mountains this winter, Monadnock in New Hampshire and Greylock in Massachusetts.
On Monadnock, the temperature was in the 20s. I started off with a wool zipneck, a light fleece over it, and a hat and light-weight gloves. On the bottom, I had ultralight synthetic longies under light nylon pants. The fleece and the hat came off as the trail started to steepen. Shortly after that, I rolled up my sleeves and pulled down the half-zip on my zipneck. I kept the gloves on the entire journey. Turning around just below the summit, I put the fleece and hat back on and descended in comfort.
A week later, on Greylock, it was 4 below zero. I wore the same wool zipneck and fleece, with a thin, quilted vest between. Again the fleece came off quickly, and I eventually unzipped the vest and the zipneck. At the top, I put the fleece back on, added a down "puffy" jacket with a shell over it and a warmer hat -- all of which kept me warm on the windy descent.