Dehydration is common among athletes, soldiers, and those that are physically active, and it occurs in both hot and cold environments. Most people do not account for the fluid needs during exercise in the cold, and thus, are at an increased risk of large body mass losses during activity. Below are mechanisms of increased body mass loss during exercise in cold environments and recommendations to minimize these losses.
• During exposure to cold environments, the body has a decreased sensation of thirst and often people will voluntarily restrict fluid intake. This voluntary restriction of fluid intake quickly leads to increased levels of dehydration, especially when people are performing intense or prolonged exercise in cold environments.
• Scientific literature supports an increase in diuresis during exposure to cold environments. The increased diuresis causes an increase in fluid losses that may not be accounted for in people exercising in cold environments.
• Another factor that often leads to large fluid losses during exercise in cold weather is the clothing that is worn. People are encouraged to match clothing (layers, amount of insulation, etc.) to the expected level of intensity. Someone doing light intensity exercise in cold weather will require more insulation than someone doing intense exercise. Increased insulation at a given intensity level will increase a person’s sweat rate, thus causing increased amounts of fluid losses during activity.
• Fluid losses during respiration are increased during exercise in cold environments. As exercise intensity increases, respiratory fluid losses are further increased due to an increased metabolic rate, and often times air that is dry (low relative humidity). The low relative humidity causes an increase in water vapor losses during respiration. During exercise in cold environments, respiration can lead to increased fluid losses, especially during intense exercise in cold, dry environments.
• It is recommended that people exercising in cold environments make an effort to reduce fluid losses during exercise. Make an effort to have an appropriate intake of fluid; it can be water or any other type of fluid (hot chocolate, tea, other warm or hot drinks, etc.). Also, choose appropriate clothing for type and intensity of exercise. This will help minimize fluid losses due to increased sweat rates if too much clothing is worn.