It's still officially winter, but cabin fever — and a hint of spring in the air — are driving many active people outside to grab a cold run or bike ride. Meanwhile, others are dancing down mountains on snowboards or skis.
But there's a problem: many of those playing outside right now forget about hydration. They'd never skip their trusty water bottle in summer. But they don't realize that they need hydration; and perhaps even more of it, in winter.
Here's the science: First, colder air is dryer, so it must be moisturized when we breathe it; using up more of our body's hydration than when breathing summer air. In addition, that cold air has to be warmed up before it hits the lungs, which takes up more moisture, as well as energy. In addition, if you're at altitude in the mountains, there's not as much pressure on your blood vessels, so they relax slightly. That makes you need even more water.
The big problem in winter is you often don't feel thirsty, even though you may actually be dehydrated. Some of the complications from winter dehydration are that you become more susceptible to frostbite because you don't have as much warm blood circulating or as much moisture in the tissues. In extreme cases — and it doesn't take much to get very dehydrated in winter — you can get dizzy and lightheaded, easily fatigued and chilled. If you're feeling unusually cold, if your urine is darker than normal, if you have dried white "froth" at the corners of your mouth — it's way past time for a water break.
Because obvious symptoms of dehydration, such as thirst, may give you no warning that you need liquid fast, it's best to put winter hydration on a time schedule. First, use a thermal bottle if possible, and fill it with warm water. It will be more comfortable to drink, and you won't have to use extra moisture to warm it up inside your body. Think of drinking at least a cup of water every hour. If you're actively playing outside, take a hydration break at least every two hours, where you can consume at least a quart of water. While plain water is best, liquid intake can be in the form of soup, herbal tea, or even partially augmented by some hot chocolate (a quart of the stuff would contain far too much sugar). But forget about coffee, black tea or alcohol. These are diuretics; they will cause you to eliminate water from your body; which can also disguise the tell-tale deep yellow color of dehydration.
If you keep yourself well hydrated in winter, you'll enjoy the cold weather much more, and be a lot more physically capable while playing in it outdoors.