The winter season is here and with this comes new sports (skiing, ice skating, sled riding) and activities (shoveling snow).  Since our ability to adapt to prolonged cold exposure is much less than our adaptability to heat exposure, performing these activities in cold weather places greater stress on the body.  Understanding why this happens can help you to prevent problems from occurring so you can enjoy the winter season and continue exercising even in the cold.

Conserving body heat is the name of the game

The body is always losing heat because heat transfers from the body to the environment, so the colder the environment, the more excessive the heat loss will be.  Blood vessel constriction occurs to conserve core body temperature and shivering works to increase body heat in extreme cold. 

1. Blood vessel constriction will decrease blood flow to the extremities (arms, legs, fingers, toes) making them susceptible to frostbite.  Muscle strain may also occur because in order to function properly, muscles need to be warm and without normal or increased blood flow, they will become cold, tight, and will strain easily.   

2. Shivering of the muscles will occur in an effort to increase blood flow to ultimately produce more body heat.  Shivering is observed at rest as well as during exercise and will cause oxygen consumption to be proportionately higher than when the same exercise is performed at a warmer temperature.  Thus, fatigue will occur much quicker when performing activities in the cold.

Dehydration is also a problem

It is a well known fact that dehydration can happen in extreme heat due to water loss through perspiration.  However, it is just as much of a problem when exercising in extreme cold.  In this instance, greater water loss occurs not only through perspiration (sweating), but also through expiration (exhaling).  This is because as air enters the body, it needs to be warmed and the colder it is, the more your body has to work to accomplish this, which results in expelling "humidified" air when breathing out.  You can compare it to an air conditioning unit- it's the same process in reverse, however water is a product of both.  Anyone who has seen a window AC unit when it's extremely hot knows that a large puddle of water will collect under it.  The hotter it is, the more water will be produced and the same goes for humans- the colder it is, the more water will be expelled when breathing.  The mouth will become dry, the throat will burn, and the respiratory passages will become irritated, and dehydration will eventually occur.  

Something else to keep in mind

Interestingly enough, a person with a higher body fat percentage will be better off than one with a lower percentage.  This actually is in line with the fact that the more body heat you conserve the longer you can tolerate the cold.  The extra body fat (subcutaneous fat)  will act as insulation and will preserve body heat longer.  This is why mammals living in the Tundra have very high body fat- think polar bears and walruses.  In light of this, many of the following tips for staying warm in the cold are related to clothing that will preserve body heat.