Dear GeezerJock Doc: I live in the Great White North. What advice do you have about exercising outdoors in winter?

Great question. first, let's dispel a myth. Frigid air won't freeze your lungs. By the time cold air passes through your nose and mouth, it's been warmed to about 80 degrees. So that's not a concern when training in cold weather (except if you have asthma, which can make exercising in the cold a difficult task). If we think about it for a moment, it becomes obvious that speed skaters, cross country skiers and downhill skiers all train outside, on occasion, in temperatures well below zero. It's just not that big an issue. That said, there are a number of things to be concerned about when you're training hard in very cold weather.

First and perhaps most obviously, you need to dress properly. Don't wear cotton; because it retains sweat and other moisture. Wear synthetic fibers, such as wicking shirts. Also, what your mother always told you about wearing a hat is true. We lose most of our heat from our heads, so the colder it gets, cover more and more of your head. When it gets below zero, I recommend wearing a balaclava or other protection for your face. Know also that the wind chill is not just a statistic, so that we can have more to ta lk about when discussing the weather. Your body, especially exposed skin, is more attuned to the wind chill than the actual temperature. Dress for the wind chill.

Second, be sure to hydrate yourself. It's counterintuitive (because we don't seem to sweat as much in winter weather) but cold air tends to be drier than hot, humid summer air. Keeping our bodies warm requires a lot of calories, so you need to make sure that in addition to drinking enough, you've taken in enough food.

Finally, be careful of slipping on snow and ice. It's not worth it to get in an outdoor run when that arm you break may keep you from running outside again for several months. When it's too slippery out to run or bike, find an indoor alternative such as a treadmill or exercise bike. Or if you simply must be outdoors, modify your aerobic exercise. Instead of running, for instance, you could go snowshoeing or cross country skiing. Both activities burn more calories than almost any other exercise you can think of.

Written by orthopedic surgeon and Masters sprinter Allan Tissenbaum, M.D., GeezerJock Doc is a forum for your questions about injuries, exercise and getting older. Submit questions to geezerjockdoc@geezerjock.com or mail to GeezerJock Doc, 2033 W. Hutchinson St., Chicago, IL 60618.