For some of you, winter exercise is just another daily adventure, especially if you live in a northern climate. For others, the thought of beginning an exercise routine in the midst of snow, sleet and road salt, it can be overwhelming. Today’s entry is going to be a gentle reminder for all of you. Dehydration and lack of proper nutrition during cold weather can be dangerous.
Water is an essential component for all of the processes the body completes each day. Approximately 70% of the body is water, mostly stored in the tissues at the cellurlar level. Water is essential for the micro processes that take place in our bodies every day. Without proper hydration, these processes don’t work nearly as well and in extreme cases, stop working all together. Our kidneys regulate the amount of water loss through urine output while thirst and hunger can help regulate daily water volume. Athletic performance decreases with the loss of 2% of bodyweight and more than 2 litres can be lost through exercise!
During exercise the heart rate increases, plasma osmolality increases (osmolality is a measure of the concentration of things like sodium, potassium, glucose and other ions in the blood) , there is a decreased blood flow to the skin (for cooling) and a resultant increase in core body temperature ( a core temp too high can be dangerous!).
Dehydration is indicated by urinary markers such as a reduced urine volume, a high urine specific gravity (USG), a high urine osmolality (UOsm), and a dark urine color (UCol) . To a person, dehydration may look or feel like irritability, headache, fatigue, Weakness, dizziness and nausea. Dehydration negatively affects training, competition and recovery.
The goal is to replace 100% of sweat lost during exercise; that’s about 1/2L of fluid per kg of weight loss. The American College of Sports Medicine (ACSM) recommends 125 ml (5 ounces ) every 20 minutes. Be aware that technology (clothing) may inhibit an appreciation of sweat rate or water loss and cold weather diminishes the thirst mechanism. Staying safe and healthy during cold weather depends on your awaress, recognition and education.
Energy expenditure in adverse weather (snow/ice) is two times greater than on a regular surface (same speed—walking). The heavier clothing worn to protect a person from the elements increases energy expenditure. Vasoconstriction reduces blood flow to peripheries (arms and legs) and thereby decreases fat utilization. Glycogen utilization increases in cold weather which results in fatigue.
A person’s rate of exercise in the beginning of a session can maintain body temp. With a prolonged session, the stored reserves (glycogen) will be depleted resulting in fatigue. With fatigue will come a decrease in exercise rate followed by less muscular activity. The resultant lower body temperature is a precursor to hypothermia, a potentially fatal outcome if not handled properly.
All of this means the body’s need for energy/food increases during cold weather exercise. Obviously the challenge is to keep energy sources from freezing, ensure ease of access/consume and be palatable. A food source with high carb content is recommended. Eat before leaving on an outdoor run (~2 hours prior) to replenish liver glycogen. During the session consume 30-60 grams of carbs every hours to maintain blood glucose levels.
A year-round outdoor exercise program is very achievable if a person learns about the importance of how hydration and nutrition affect the body in cold weather.