Hydration Matters for Winter Training and Racing. How to nail your strategy.


Paying attention to hydration needs is a year-round task for athletes. However, because people generally associate a need for fluid replacement with the summer sun, winter often takes a backseat in terms of hydration considerations. Winter is not a time to forget about proper fluid, carbohydrate and electrolyte intake if you want to perform at your best.

If you are signed up for the Power of Four, the Grand Traverse or any other winter endurance race (or if you are training in cold weather), you should be especially interested in your hydration strategy. Let’s get started.

Physiological Responses to Cold Weather

When the temperature drops, the body must adjust to maintain homeostasis (the body’s “physiological happy place.”) There are several things that occur in the cold that affect both nutrition and hydration. First off, cold air tends to also be dry air (or less humid air). The body responds by increasing breathing rate which, along with the decrease in humidity, increases respiratory water losses. It is not uncommon for people to lose an extra 1-2 liters per day of water in cold climates. Altitude also magnifies such adaptations and losses.

People also urinate more in both cold and high altitude environments. When temperatures drop, blood vessels constrict. This happens because your body is trying to conserve heat. This results in the need to pee more frequently (more formally called Cold-Induced Diuresis). At high altitude, urine output also increases (formally called High-Altitude Diuresis). The reason this happens is because having less fluids onboard results in thicker blood and subsequently more concentrated hemoglobin. Hemoglobin supplies oxygen to working muscles and tissues, which make its higher concentration valuable. Bottom line, both of these physiological mechanisms result in greater fluid loss through urination (which is a little bit of a double whammy if you live and training in mountains).

When we exercise outside in the winter, we also tend to dress in warm clothes. Our layers of Patagonia, Columbia, Strafe, North Face [or insert any other personal fashion favorite here] create microclimates. The microclimates both keep us warm and provide a perfect environment for sweating. While sweating normally might be slightly less extensive in the winter than the summer, with the layering climate, the effect it isn’t really that different. Thus, we are still losing water through sweat. To further confound the issue, cold weather suppresses our desire to drink. Thus, we are still sweating, yet have a muted thirst sensation.

Finally, the body must maintain a core temperature of 98.6 degrees Fahrenheit. In cold environments, this becomes harder to maintain. The extra work our body has to do to stay warm results in greater use of carbohydrate stores (glycogen). When shivering is required to prevent dangerously low temperatures (i.e. ≤95 degrees Fahrenheit), the body taps even more of its glycogen stores to keep up. As an aside, hypothermia becomes more likely when the body is dehydrated. This increased risk is the result of the decrease in blood volume mentioned above. Again, you need to hydrate for long, endurance events to not only promote performance, but also to protect health (important especially in the Grand Traverse, which is largely in the backcountry).


What this all means for hydration

Really, hydration needs aren’t that radically different in the summer and the winter. Yes, we sweat more in the summer, but we also lose more water through respiration and urination in the winter. Furthermore, we are less inclined to take in fluids in the winter even though we are still sweating in our warmer clothing. Last but not least, hypothermia is more likely if you don’t take care of your fluid needs in the cold.

Tips for Dialing your Hydration Plan

Collecting Data

There are a few things you can do to dial your winter nutrition. First things first, collect data and understand your needs. The first step in developing an understanding of what you need to be taking in is to perform a sweat rate test. Click here for directions on how to do this easy assessment. This test will give you information on how much fluid you are losing through sweat. In turn, this will help you to better define what you need to be drinking in cold weather (you will need to do a separate test in hot weather as environment does affect sweat rate).

Another step you can take, is to schedule an advanced sweat concentration test. While sweat rate is one factor, sweat concentration is a second and equally important factor. Sweat concentration is the amount of sodium you lose per liter of sweat. The difference between athletes’ sweat concentration values can range between 200mg of sodium lost per liter sweat to 2200mg of sodium lost per liter. Because electrolytes (sodium in particular) are important to maintaining performance and the hydration equation, getting your personal number is a step in the right direction. Did I mention that you only need to get a sweat concentration test once? That is because sweat concentration is a genetically pre-determined factor that is unlikely to change much during adulthood regardless of training, temperature or altitude.

Tactical Tips

Now that you know you need to drink, here are some practical tips to put your hydration plan into action. The first challenge I have come across in single digit temperatures is making sure my hydration doesn’t freeze. Adding electrolytes can help keep your fluids in liquid form. Nuun and Precision Hydration both make effervescent tabs [with electrolytes and without carbohydrates] that can help prevent freezing. For a 15% discount on Precision products use KE15 at checkout. Sports drinks for longer training and racing sessions [with both electrolytes and carbohydrates] also help prevent freezing (one of the biggest benefits of sweat rate and concentration testing is picking the sports drink with a concentration that most closely matches your needs per hour).


The next tip is to fill your bottles with hot water (along with electrolytes). You will be amazed at how quickly hot turns cold (just be sure to feel your bottle before sipping). You can also carry a thermos if you are doing something that involves a backpack and an ability to stop. This won’t work for running, which is where neoprene sleeves for camelback-type set-ups come in handy. Here is a link to said sleeve. Make sure that you keep the sleeve close to your body as your natural heat will help keep the liquid from freezing. Let’s say you are lucky enough to have the ability to go uphill or do Ski Mountaineering (if you don’t know what this is I highly encourage you to find out and check it out). There are some awesome accessories that make hydration more doable. Here is a link to a water bottle carrier that sits right on the front of your backpack (and is a constant reminder to take a sip). Ultimate Direction also makes a pack with a front pocket that will fit a collapsable water bottle (for training). For racing, it generally makes the most sense to use a bladder inside of the backpack (route the hose close to your body to prevent freezing). In ultra cold temperatures, I will also use a Function Before Fashion front pack carrier to carry my bladder (I put the pack over an initial base layer and below an outer layer. I take sips from the hose and put it back after each sip to prevent freezing (my body heat is what keeps the hydration warm in this case.

Another great tip is to start cold weather races and big training sessions hydrated. Pre-loading is one way you can ensure you are ready to go on the hydration front when the gun (or Garmin) goes off. If you are unfamiliar with the concept of pre-loading, here is a blog to help you better understand the research behind this tactic. My favorite pre-load product is Precision’s 1500. I will take this in the night before and morning of a big ski mountaineering event that involves a long, cold day and a lot of vertical. Another tip is to plan a stop for hot drinks or have a crew to hand you something warm during a race (in the Power of Four race, it is always great to have a crew waiting at Highlands with some fresh bottles, etc.).

In Conclusion

No matter your age, level or ability, it is always fun to perform well. Whether it is an adventure with friends, a big nordic or skimo race or simply training for the next triathlon season, feeling strong never disappoints. Hydration is a detail that will help immensely if you pay attention to it. It is also pretty easy to figure out and execute. That said, dial your year-round hydration to optimize your ability and maximize your enjoyment of your sport. Happy training and racing!


Bernardot, Dan. (2018). High Altitude and Cold Weather Sport: Are there nutritional concerns? American College of Sports Medicine. Retrieved from: https://www.acsm.org/blog-detail/acsm-blog/2018/02/19/high-altitude-cold-weather-nutritional-concerns.

Karpinski, C. and Rosenbloom, C. (2017). Sports Nutrition: A Handbook for Professionals, 6th Edition. Chicago: Academy of Nutrition and Dietetics.

Marriott, BM and Carlson, SJ. (1996). Nutrition Needs in Cold and High-Altitude Environments: Applications or Military Personel in Field Environments. Washington DC: National Academies Press.

Masri, Lilah and Bartlett, Simon. (2011). 100 Questions and Answers about Sports Nutrition and Exercise. Sudbury, MA: Jones and Bartlett, LLC.

Stavinoha, Trisha. (2019). Hydration in the Winter. USA Triathlon. Retrieved from: https://www.teamusa.org/USA-Triathlon/News/Blogs/Fuel-Station/2019/January/30/Hydration-in-the-Winter.