If you want warm hands, put a hat on!
You may have heard of this old mountaineering adage which invites you to keep your head warm when it’s chilly to avoid cold and uncomfortable fingers. It turns out to be good advice to follow, but do you know why?
When the outside temperature drops, our body temperature tends to fall as well. As a natural defence, some specific parts of our brain give the order to reduce or even stop the blood flow in the extremities. Blood conveys heat within our body, so reducing the amount of blood going to the extremities will also reduce the amount of body heat escaping from the hands to the environment. As a consequence, our blood remains in the trunk regions, which helps maintain our vital organs at a warm, optimum temperature. This can be a life-saving trick in some conditions but the side effect is that our fingers cool very quickly and can even become painful when approximating the outside temperature. There are a lot of tiny, natural temperature sensors in our hands which provide important information about how cold (or hot) things are around us. So, not only hands are the first regions to cool when it’s cold, but they also “feel” the cold more than other body sites. Thus, they are often responsible for the general discomfort in cool situations.
To keep carrying heat to the hands, the blood has to keep flowing there. To maintain a good blood flow, the sensors around our main organs need to indicate a warm, optimum temperature so that our body has no reason to sacrifice the extremities by reducing the blood flow. One of these sensors is in our brain, and it has a strong influence on the regulation of the blood flow. In addition, an important amount of body heat escapes from the head. Therefore, if you can maintain an optimum “internal” temperature by keeping your head warm, then this should in turn help you keep your hands nice and warm too. So really, in the cold, if you want to keep your hands warm for longer, put a hat on!