Cold weather is upon us and as you begin to bundle up for your outdoor exercise please make sure you don’t become dehydrated! You might think – dehydration, in cold weather, really? Yes – really. Basically, you do not feel as thirsty as the temperatures drop. So when you don’t feel thirsty you won’t consume as much fluids which will then cause dehydration.

With every breath in the cold air you lose a great deal of fluid. Then when you add on the amount of extra clothing you are exercising in you are still perspiring and typically your body will work much harder than it normally would due to the extra weight. Don’t forget that sweat evaporates quicker in the cold, dry air.
Your body is compromised of 60-65% water and as that percent drops ~2% you will become dehydrated. Once dehydration sets in you can see a decrease in your performance. This will slow down your recovery rate and minimize some of your training adaptations as well.
Something that needs to be taken into consideration is how your thirst response reacts in cold weather vs. warm weather. During the lower temperatures our thirst response doesn’t activate as much leaving us not feeling thirsty. This can become a very big problem during prolonged exercise in cold weather.
I’ve had an athlete compete at 2010 Ironman Florida who has experienced this lesson first hand. He figured since it was cold he needed to adjust his nutrition and did not need to consume as much fluids. Let’s say that lead to a very unhappy ending. You need to be aware of your sweat rate and how it is affected by different temperatures. Your ability to adapt will help you maintain a higher level of performance.
Every athlete’s sweat rate is different. Your sweat rate depends on your body size, exercise intensity, climate (temperature, wind, etc.), physical fitness, clothing, gender, and how you acclimated to your current conditions you are exercising in. If you know your current sweat rate make sure you monitor it during your training sessions in the cold weather. If you do not know it use the below equation and instructions to determine it. This would be good for those wanting to double check theirs in any temperature.
*CALCULATE YOUR SWEAT RATE: To begin, record your nude body weight prior to exercising. When you are finished exercising, dry yourself off the best you can and record your nude body weight again. Record what and how much you consumed of fluids during your exercise. Subtract your pre-exercise weight from your post-exercise weight and add the amount of fluid you consumed to that number. This will give you the amount of fluid you lost while exercising. Then you need to divide that number by the amount of hours you exercised for and that will equal your sweat rate. Be sure to record the weather conditions as well, as to see how this may fluctuate.
1. ________ Record your nude body weight prior to exercise.
2. ________ Record your nude body weight (dry off best you can before recording weight) after exercise (convert weights to ounces; 1 lb = 16 oz).
3. ________ Record how much fluid you consumed during exercise (use ounces).
4. ________ Subtract lines1 & 2 from above for total weight loss and add line 3. This is the amount of fluid your body lost while exercising.
5. ________ Take the number from line 4 and divide it by how many hours you exercised for. This will give you and idea of what your sweat rate is.
Moral of the story is dehydration is not just something to worry about in the heat, but at all temperatures. Be sure to monitor your fluid levels, know your sweat rate, and pay attention to your rate of perceived exertion during your workouts. Be safe and happy holidays!
Nick Suffredin previously was a Scientist at the Gatorade Sports Science Institute where he worked on testing elite professional athletes to enhance their hydration practices and nutrition intake to improve their performance. He has been part of human performance advisory boards as well as currently provides endurance and nutrition coaching. 

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