Exercising in the Cold Weather
by Jeffrey A Zlotnick, MD, CAQ

The winter months drives most people to do their exercise activities indoors; however there are a number of people who will continue to be active outdoors in the cold. I'm not just talking about the typical winter sports such as skiing and skating, I'm talking about running and even bicycling! These sports can be enjoyed year round if you know what precautions to take.

The number one problem that any person who wants to exercise in colder temperatures needs to be aware of is hypothermia. When you exercise, the body produces heat in the central part of the body known as the core and that core temperature needs to be maintained within a very limited range to protect the heart and the brain. If that temperature start to gets too high, the body will start going into hyperthermia or heat stroke; too low and the athlete risks hypothermia and frostbite.

The symptoms of hypothermia can start subtly, but can be quite severe. As that body core temperature drops, the body will try to do things to maintain it, the most notable being shivering. Just to give an example of what can happen, below is a list of what symptoms a person can expect as their body temperature drops from the average normal of 98.6 degrees:

• 95-98 degrees: Intense shivering & inability to perform tasks
• 90-95 degrees: Violent shivering, inability to speak or think clearly, amnesia
• 85-90 degrees: Shivering now ceases, muscles become rigid, person becomes semi-conscious
• 80-85 degrees: A person can go into a coma, heart-beat irregularities
• Less than 80 degrees: Death

There is a very intricate mechanism the body uses to maintain that core temperature in that narrow range. As a person exercises, the body produces heat from the activity in the muscles. If the core temperature starts to become too high the body will send more blood flow the skin where that excess heat can be dissipated. The body dissipates heat by producing sweat which then evaporates taking the excess heat with it. Maintaining this balance can get very complicated in extremes of weather. In the cold, a person needs to wear warmer clothes to not only maintain that core temperature but to protect a person's limbs, especially those delicate fingers and toes, from frost bite. If the clothing is too thick, the sweat will simply build up in the clothing and person can actually go into hyperthermia even if the temperature is below freezing outside. Too little clothing and the sweat will dissipate too rapidly causing the core temperature to fall rapidly and hypothermia will ensue. So, it's recommended that a person wear clothing that can shunt sweat away from the body so it can be dissipated, but not too rapidly. There are many synthetic materials out there that can do this quite well, and certain natural fibers, such as wool, are quite good at this. Cotton is not recommended because it tends to hold the sweat in it. Once that happens, the clothing itself begins to drop in temperature taking a person's core temperature with it.

Layering of clothing is very important. There needs to be a base layer that wicks the sweat away from the skin and an external layer that can both let the sweat evaporate and maintain warmth. Heat loss is accelerated in windy conditions, or activities such as skiing or cycling, because of the chilling effect. In these conditions it's recommended to wear an outer shell, or jacket, that is wind proof yet can breathe to allow that sweat to dissipate and not be trapped beneath it. There are many different types of shells (jackets) available that can perform this function well.

Another area of significant heat loss is a person's scalp. Most athletes will wear either a wool or synthetic cap to prevent this. Some athletes actually want to leave their scalps exposed to help with preventing heat build up and just wear a head band to protect their ears from frostbite. It's also important to protect those areas that are prone to frost bite such as the finger and toes. Gloves and socks designed for cold weather exercise are best.

It's also a myth to believe that just because it's not hot outside that it's not important to maintain fluid balance. A person needs fluid to maintain blood flow and be able to produce sweat to dissipate heat. If a person is dehydrated, the sweating will stop causing the body to decrease blood flow to the limbs. Once that happens, frostbite can start. Other things to avoid are alcohol because despite that sense of warm it may give you for a moment; it can lead to dehydration and the problems mentioned above. Also, smoking decreases blood circulation which greatly increases the risk for frostbite.

If you start to experience any of the symptoms of hypothermia the best thing a person can do is get into a warm place. If the symptoms seem more severe, then it's imperative to get to a hospital. It may be a good idea to exercise with a partner so if one person starts feeling poorly, the other can get help. If you're out in the open, using blankets and sharing body heat are a good form of first aide. Just remember, excessive rubbing and jarring can actually make things worse rather than better.

So, I think you can see while there may be some precautions you have to take, exercising outdoors in the cold can be fun and quite exhilarating. So, dress right, drink plenty of fluids, and go outside and enjoy!