Jack asks: How can I stay warm on my runs when it is cold outside but still keep from sweating too much once I get warmed up?
This is the paradox of winter runners - keeping warm while avoiding overheating. From my perspective, the key for exercisers who produce a lot of metabolic heat is to layer appropriately and wear clothing that can be vented to allow extra heat to escape before you start to sweat heavily. There are great clothes available for outdoor cold weather activity that seem to improve with each generation of materials and design.
Clothing layers add up to insulation. Wool and synthetic materials are best as they move water away from the skin to the outer layers, maintaining a dry insulating air layer next to the skin. Wool retains its insulating properties even when wet with sweat, and many of the new wool products do not itch.
In contrast, cotton hangs on to water and conducts heat out of the body, which becomes a problem if you stop running from injury or exhaustion and cannot get to warm shelter.
Sometimes it is difficult to nail the number of layers for a given condition. That is where zips that vent the layers make a difference. Most of my activewear is zipped, and my outer shell has zippered pocket, armpit, and front vents to allow heat and water vapor to escape. It also has a hood that can be tightened down for extra warmth.
A hat or cap can help keep you warm in the cold and can be the difference between a comfortable run or not. The head makes up about nine percent of the body surface, and it has high blood flow. So if you are hot, removing your hat will allow a fair amount of heat to escape the body. The same is true for your hands; heat loss can be high due to the extensive blood vessel network in the hands. Mittens work well because the finger grouped together keep each other warm, and when mittens are removed the exposed hand becomes a heat-loss surface.
On cold days, I wear or carry a balaclava and ear muffs to put on under my usual cap. I have several thicknesses of caps and mittens to match the day. I also carry liner gloves to add to my hands, if needed, for cold or to wear alone if my mittens get too hot.
A shoe that is windproof will usually keep your feet warm if you wear wool or synthetic socks. Again, cotton socks are not for cold-weather activity. Some companies make winter running shoes with Gore-Tex or similar materials that block the wind when you are moving and keep your feet warm. I use a neoprene boot cover for Nordic skiing in the cold, and there may be similar products for running.
It is also important to protect your eyes in the cold. A pair of clear or light yellow lens sport glasses work well in the low light and dark of winter and your usual sport sun glasses work well during the day light hours. Although relatively rare, frostbite of the cornea of the eye can cause blindness in that eye.
With contemporary outdoor clothing it is relatively easy to stay comfortable on the run, even in really cold conditions.
