When studying the animal kingdom, one finds that humans may be described as warm-weather, tropical animals that neither adapt to nor tolerate cold weather.
As we know, however, humans still must work and exercise in such environments.
In order to cycle effectively outdoors in the winter, you need to know how cold affects you and whether it alters your fluid and nutritional requirements during exercise.
While cycling, you're body is generating 10 to 15 times the heat it would while at rest, which is more than enough to maintain your body temperature in the cold.
When you are dressed properly, under most circumstances cold weather has little or no effect on your body temperature because your energy production overrides the cold temperatures and wind chill.
Some athletes who exercise in the cold have higher caloric needs. Scientists have found that this is primarily due to the various cycling conditions encountered, and amount and type of clothing and shoes worn.
For example, it is known that riding a heavier bicycle and the added wind drag of more clothing and heavier shoes will increase your energy cost and energy needs. By simply adding an additional 100 to 200 grams to each shoe causes a 1 percent increase in oxygen consumption during cycling.
Eat for Heat
While there is no need to significantly increase your caloric intake during cold weather, you may want to consider taking in a small snack before your ride.
Once you begin digesting the food, this will add some heat to your body by metabolism and help keep you warm. As in the summer, your fluid replacement needs are crucial to your performance while training.
While in the summer you lose a tremendous amount of fluids through sweating, in the winter you lose more fluids while breathing cold air, which must be warmed and moistened in your throat and lungs.
As you exhale, you lose lots of water, which is why you can see your breath during heavy exercise. The humidity content of cold air is much less than warm air. This is why your throat feels much drier in the winter.
If a person is active under these cold, dry conditions, the amount of moisture lost through respiration increases significantly and must be replaced.
Fluids on the Loose
As a result, it is essential to keep up with this loss with frequent fluid replacement during the day and while cycling. In addition, you lose more water through increased urine production in the cold. The medical community calls this phenomena cold dieresis.
As in the summer, winter dehydration can lead to fatigue, which will affect your ability to train or compete at your optimum level. And as in the summer, a decrease in your blood volume caused by sweating and insensible water loss from breathing means less blood flow to your skin and extremities.
This will lead to a more rapid cooling of your body and possible increase in susceptibility to hypothermia and/or frostbite.
Fluid temperature is also a concern to many while exercising.
A liter of water heated to 130 degrees Fahrenheit (about as warm as you can drink) would provide approximately 18 kilocalories of heat to an individual, while a liter of water at near freezing would absorb about 35 kcal of energy to heat it up to your normal body temperature.
From this you can see that drinking warm water will add very little energy to your body, while drinking cold water can rob your body of calories. But there is the thirst-quenching aspect of cold water that makes it appealing during exercise.
With the adequate heat production that occurs during exercise, the intake of cold water will do you no harm. But if you are feeling chilled, it would be best to avoid a further caloric drain—if the choice is between cold water and no water, drink the cold water.
One way to avoid this dilemma is to carry your water under your jacket and close to your body to keep it from getting too cold.
A CamelBak drinking system may be advantageous during winter cycling or skiing, since it can be worn under a training jacket.
Roughly speaking, there are three times when a cyclist in training in the winter should drink: when he is thirsty, when he isn't thirsty and in at any point in-between.