Cold temperature can cause life and limb threatening cold-related disorders. Cold-related disorders can be systemic or local.
Hypothermia is a systemic response to cold and occurs when the core body temperature drops below 95 degrees F. It can begin even when air temperatures are at 50 degrees F. Hypothermia requires immediate medical attention.
Signs and symptoms of hypothermia include: chills, fatigue or drowsiness, pain in the extremities, euphoria, slurred speech, slow and weak pulse, shivering, and collapse and/or unconsciousness.
Frostbite is freezing of local tissues that can occur if ambient temperature is less than 30 degrees F. Frostbite must be treated as a burn and requires medical treatment.
Frost nip and trench foot are skin disorders resulting from extreme cooling of the skin and underlying tissue, but without actual freezing of the tissues. Damp clothing accelerates heat loss, which causes frost nip and trench foot. Frost nip can also occur when the wind chill is –22 degrees F.
- Environmental conditions that must be considered in the management of cold stress along with exercise demands are air temperature and air speed. Personal protective practices are recommended for exercise at air temperatures below 50 degrees F. Proper clothing is the primary protection against cold-related disorders. Layering of clothing is always the recommended choice with physical activity outdoors. The amount of layering depends on the intensity of the activity and the temperature. Generally, each quarter-inch of clothing adds one layer of insulation. Any exposed skin, however, is still at risk for excessive local cooling and can lead to frostbite.
- The following are examples of how much layering of clothing is needed if the air temperature is 20 degrees F. If you are going to do a high intensity activity like running or speed biking, you will need approximately one layer (a quarter-inch thick total) of clothing. If you are going to do a light intensity activity like walking you will need at least three layers (three quarters of an inch thick total) of clothing.
The following practices are recommended for exercise at air temperatures below 50
degrees F:
- Plan your activity to avoid fatigue at a location removed from a warm recovery station. For example, if you run outdoors on an off-road (e.g., trail) setting, you may want to consider an alternative, pedestrian-friendly route through a neighborhood that offers potential shelter (e.g., coffee shop) along the way should it be needed.
- Anticipate, wear, and adjust as necessary proper clothing. Key word here is layers!
- Seek relief from cold stress exposure when you experience sensation(s) of extreme discomfort, especially at the extremities; fatigue or weakness; or loss of coordination.
- Frequently drink warm, caffeine-free fluids containing carbohydrates. Not only will this help keep your core temperature above 95 degrees F, but this will also keep you hydrated and with ready energy. For example, pour your lukewarm sports drink in an insulated container when doing outdoor exercise.
- Change wet clothing immediately, especially if the air temperature is less than 36 degrees F.
- Seek medical advice for repeated or unusual intolerance to cold, such as repeated episodes of frost nip, appearances of welts, or severe shivering. It is recommended to have medical approval for exercising at wind chills of less than 11 degrees F.
Bernard TE. Chapter 24, Environmental Considerations: Heat and Cold. pp. 213-216 in American College of Sports Medicine’s Resource Manual for Guidelines for Exercise Testing and Prescription, 4th Edition. Baltimore: Lippincott Williams & Wilkins, 2001.