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.
But Winter (or trips to colder parts of the world for events) is not a time to forget about proper fluid, carbohydrate and electrolyte intake if you want to perform at your best.
There are quite a few reasons to not only consider your needs, but also to dial in your cool weather drinking strategy.
Let’s get started...
How our bodies respond to cold weather
When the temperature drops, your 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 your breathing rate which, along with the decrease in humidity, increases respiratory water losses. It's not uncommon for people to lose an extra 1-2 liters of water per day in colder climates. Altitude also magnifies these 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 (High-Altitude Diuresis). This happens because having less fluids onboard results in thicker blood and subsequently more concentrated hemoglobin.
Hemoglobin supplies oxygen to your working muscles and tissues, which make its higher concentration valuable.
The bottom line is that both of these physiological mechanisms result in greater fluid loss through urination.
When we exercise outside in the winter, we also tend to dress in warm clothes. Our layers create 'microclimates'. The microclimates both keep us warm and provide a perfect environment for sweating.
So, despite the cooler weather, we're still losing reasonable amounts of water through sweating. To further confound the issue, cold weather can suppress our desire to drink. We're still sweating, yet have a muted thirst sensation.
Finally, the body must maintain a core temperature of 98.6 °F (37°C). In cold environments, this becomes harder to maintain. The extra work our body has to do to stay warm results in a greater use of our carbohydrate stores (glycogen).
When shivering is required to prevent dangerously low temperatures (i.e. ≤~95°F, ~35°C, the body taps even more of its glycogen stores to keep up.
What this all means for your hydration strategy
Really, your hydration needs aren’t that radically different in the Winter than they are in the Summer. Yes, we sweat more in the summer, but we also lose more water through respiration and urination in the winter.
We're also less inclined to take in fluids in the winter even though we're still sweating in our warmer clothing (or warm indoor training environment).
Last but not least, hypothermia is more of a risk if you don’t take care of your fluid needs in the cold. That's as a result of the decrease in blood volume mentioned above.
Collecting data to understand your fluid/electrolyte losses
First things first, collect data and understand your own individual needs.
The first step in developing an understanding of what you need to be taking in is to measure your sweat rate in different cold weather scenarios to get a rough idea of the volume of your losses in those conditions.
This will help you to better define what you need to be drinking in cold weather (you will need to do separate calculations in hot weather as environment does affect your sweat rate).
Your sweat rate is one important factor, but your sweat sodium concentration is another - equally important - part of the hydration equation.
Sweat sodium concentration
Sweat concentration is the amount of sodium you lose per liter of sweat. The difference between athletes’ sweat concentration values can be significant - ranging between 200mg of sodium lost per liter of sweat to as much as 2,200mg of sodium per liter.
Because electrolytes (especially sodium) are important to staying hydrated and maintaining performance, understanding your rate of loss can really help you dial your electrolyte intake in. If you want to find out exactly how much you're losing, you can schedule an Advanced Sweat Test at a Precision Fuel & Hydration Sweat Test Center near you. (Disclaimer: I run PH's Sweat Test Center in Aspen, Colorado).
Did I mention that most athletes only need to get Sweat Tested once? That's because your sweat sodium concentration is a largely genetically pre-determined factor that's unlikely to change much during adulthood regardless of training, temperature or altitude.
Another option is to use a few visual indicators to estimate how much sodium you're losing and then take the free Online Sweat Test to get some initial personalized advice and do some trial and error in training before potentially doing the full test to help you refine things down the line.
Practical tips on how to stay hydrated in colder climates
Now that you know you need to drink, here are some practical tips to put your hydration plan into action...
1) Making sure your fluids don’t freeze
The first challenge I have come across in really low temperatures is making sure my drinks don’t freeze. Adding electrolytes can help keep your fluids in liquid form.
And if you fill your bottles with warm/hot water (along with the electrolytes), that'll help on that front too. You'll be amazed at how quickly hot turns cold (just be sure to feel your bottle before sipping).
2) Get cold weather hydration accessories that make it easier to get fluids in
Let’s say you're lucky enough to do something like ski mountaineering, there are some awesome accessories that make it easier to stay hydrated.
This Dynafit water bottle carrierthat sits right on the front of your backpack (which is also a constant reminder to take a sip!). Getting yourself a bottle with a straw is handy too as then all you have to do is turn your head and drink!
You could also carry a thermos if you're doing something that involves a backpack and the ability to stop. This won’t work for running, which is where neoprene sleeves for Camelbak-type set-ups come in handy.
3) Start cold weather races and big training sessions well hydrated
Preloading is one way you can ensure you're ready to go on the hydration front when the gun (or Garmin) goes off.
My favorite preload product is PH 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.
To sum up, no matter your age, level or ability, it's always fun to perform well. Whether it's an adventure with friends, a big nordic or skimo race or simply training for the next triathlon season, feeling strong never disappoints.
Getting hydration right is a detail that can help immensely. It's 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.