Dress in dry layers for outdoor winter exercise

Our coldest months are upon us. January and February are typically very cold days in Southern Nevada. But people exercise and work in many cold-weather environments even here in Las Vegas. There are numerous factors that determine whether exercising in the cold will lend itself to physiological strain or injury. For the most part, however, cold weather should not prevent us from our daily physical activity routines.

Injury and hypothermia generally occur when core (deep body cavity) temperature falls too low. People with a higher percent of body fat tend to maintain this core temperature better than lean people. And although there are some differences in core temperature responses between men and women, research attributes these to differences in body fat, as well. While physical fitness does not improve the body's regulatory responses to cold, it does allow one to exercise for a longer period of time at a higher intensity level, therefore maintaining core temperature. Older adults or those with existing cardiovascular or circulatory disorders may also be less cold-tolerant than their younger counterparts and should take some precaution.

So what can be done to improve tolerance in cold weather? Since cold illnesses are caused by excessive loss of body heat during long periods of cold exposure, how we dress can make a huge difference. Wear nonrestrictive garments that allow adequate blood flow necessary to warm the body. Instead of wearing a single bulky layer of winter clothing when you exercise, wear several layers. The first layer that is in direct contact with the skin should be a lightweight synthetic or polyester material. These will dry quickly and transport moisture away from the skin to the next layer of clothing. The second layer should be wool or polyester fleece. It provides the primary insulation. The outermost layer serves to transfer the moisture back to the open air while repelling wind and rain. The outer layer is rarely worn during exercise unless it is raining or windy. It is mostly worn during rest periods.

Wearing several layers not only provides the most flexibility to adjust insulation needs to prevent overheating, under-dressing and staying dry, it also allows you the option to take layers off as the body warms up from increased activity. When clothing becomes wet, it loses 90 percent of its insulating properties. So once exercise stops, the heat being generated also stops, and you should immediately go indoors. Replace any wet clothing to prevent a drop in core temperature as wet skin facilitates heat loss.

The same principles of layering and staying dry apply to gloves/mittens, socks and hats. Keeping your head warm is critical because 50 to 75 percent of heat production is lost through the head. Also wear a knit cap and headband to cover the ears. Mittens, compared to gloves, provide greater protection from cold injuries because the fingers have better circulation when they are not isolated. Though we often do this, don't blow into your gloves or mittens. Seems like that breath of hot air warms your hands, but in the end, the vapor from the air will cause moisture that contributes to cooling. Keep everything dry at all times. Even feet perspire, so change your socks periodically.

Fluid balance can also be affected by cold weather. Exercise increases sweat loss, and if fluids are not replaced, dehydration can easily occur. When skin temperature also falls, thirst is less noticeable. So drink plenty of fluids before, during and after exercise.

Finally, if it's a cold, wet and rainy day, you might want to consider postponing your outdoor activity and find something cozy to do indoors. Rain or wind in already low temperatures makes it much more difficult to maintain our internal heat balance and may result in cold-weather injuries or reduced performance. Even in mild temperatures, there is still considerably more body heat loss with rain and wind.

But don't let the cold get you down. "Whether the weather be fine, whether the weather be not; whether the weather be cold, whether the weather be hot; we'll weather the weather, whatever the weather, whether we like it or not" (author unknown).

Annie Lindsay is an assistant professor and exercise physiologist at the University of Nevada Cooperative Extension. She conducts research and programming in adult fitness, physical activity, body image and childhood obesity prevention. Contact her at lindsaya@unce.unr.edu.