Training in the cold is, unfortunately, something that most of us have to do at this time of year. But how does your body respond to cold weather training, and what should you consider from a nutritional point of view?
Do you burn more calories in the cold? It is true that a small amount of calories are used to warm the air you breathe, but in reality the heat produced during exercise does a pretty good job of this itself. However, if your core body temperature decreases and you begin to shiver, you could expand up to 400 calories an hour shivering! Hopefully your training environment and clothing choices keep you from you reaching this point.
As a cyclist or runner you need to evaluate other factors that may increase your caloric needs during the winter months — extra clothing and weight along with snowy terrain, certainly will have an increase in your caloric needs. Research by the U.S. Army says about 10 percent more calories are needed for troops who exercise in the cold. How many calories you need is dependent upon weather, duration and intensity of your training bouts along with the increase in clothing and effort required. Keep in mind this was an Army study; subjects will have been pushed into more extreme climates then you are planning on riding in!
Training thoughts: Most cyclists are keen to lean down for race season and with the timing of your event you should be well into your base phase after the holiday season, when most of us have added a little “training weight.” Base miles, if done properly, burn a significant amount of fat, so a little extra caloric burn may not be a bad thing. Compounded with the fact that your event is long, base miles are of the upmost importance, so you have the ability to work on several performance factors at the same time.
Fluids: Fluids are extremely important during exercise in the cold. Generally, cold weather is accompanied by a dry environment, which can have a significant effect on body fluid loss.
While exercising in the heat you visibly see the sweat drip off your body. However in a cold/dry environment fluid loss through sweat can evaporate quickly, thus you are unaware of how much fluid you are losing. When you breathe in cold-dry air, your body warms and humidifies that air. So, when you exhale, you lose a significant amount of water through respiration. Additionally, your thirst mechanism can be blunted by the cold; you may feel less thirsty despite significant fluid loss, thus you need to be diligent in drinking enough fluids during cold weather workouts. 500 to 750 ml per hour is a realistic goal.
The temperature of your beverage is something to consider. A colder beverage will take energy from your body (e.g., 1 liter of near freezing water will take about 35 calories of energy to heat it up to your normal body temperature), whereas a warm beverage will provide heat to your body (e.g., a liter of warm water at 50 degrees Celcius will provide about 18 calories of heat to your body). In a very cold environment, it would be beneficial to drink a tepid or a warmed fluid replacement.