Dehydration increases susceptibility to other conditions such as hypothermia, making it more critical as temperatures plummet. Be intentional about hydrating during cold weather by understanding the issue and planning ahead.
Good hydration in cold weather maintains blood-volume and prevents hypothermia, however it requires a conscious effort. "People just don't feel as thirsty when the weather is cold," says Robert Kenefick, associate professor of kinesiology at the University of New Hampshire. "When they don't feel thirsty, they don't drink as much, and this can cause dehydration." Additionally, the drier cold air increases the amount of fluid lost during respiration and by sweating.
Winter sports frequently take place in cold and high-altitude environments simultaneously. The combination of the two creates a "double edged sword." Increased fluid loss due to rapid and deep breathing of frosty, dry air is the primary cause of dehydration at high altitude. In addition to the cold, dry air, "One of the first things to occur in response to exposure to a higher elevation is a rapid reduction in the amount of water that circulates within your body. This rapid elimination of water from your body, through urination, concentrates red blood cells that carry oxygen in your blood, and this helps to offset the thinner air at altitude," explains Dr. Christopher D. Jensen in Challenges of High-Altitude Sports.
At 6,000 feet, we can exhale and perspire twice the moisture as we would at sea level. Above 15,000 to 16,000 feet, fluid requirements often exceed four liters per day. Adding to this, many people experience a reduced thirst drive at altitude. Now pair that with the reduced thirst encountered in cold temperatures, and it becomes a clearly unreliable indicator of hydration.
Dehydration setting in faster in cold weather, paired with an unreliable thirst drive, necessitates that hydration be a conscious effort.
Hydrate before, during, and after activity. Did you catch that "before?" Yes, begin hydrating well before heading out so that you're ready for the exertion ahead. Depending on your activity, it may be impossible to maintain hydration, especially if you start out behind.
During activity, drink, every 15-20 minutes, even when you're not thirsty. Set a timer if needed. Another idea, if you're skiing at a resort, is to drink between each lift ride. Continue to replenish your hydration at the end of the day because there is a good chance you lost fluids regardless of your best effort. This will have you ready to go the next day.
Keep water handy and ready to drink. A bottle stashed deep in your pack is awkward and a frozen hydration bladder is nothing but dead weight. Prepare by making sure you have a solid hydration system.
To prevent the hose of standard hydration packs from freezing, blow the water back into the bladder between sips and stow the tube close to your body. Some suggest buying an oversized jacket and wearing the pack underneath to keep it warm, (I haven't tried this personally). Consider using a snow sports pack with insulated compartments and then add hand-warmers to the pouches to prevent the bladder and bite valve from freezing.
How much hydration is enough? We know thirst isn't an accurate indicator. While there's an excess of information and advice out there, I'll keep it simple — drink enough to produce an adequate volume (1200ml or 1.2 liters per day) of light colored urine. Yes, look at your pee and make sure it's pale yellow.
What you drink is important too. Water is best in most cases, but during extreme exertion added electrolytes may help, but don't overdo sports drinks. Soups, fruit, and herbal teas are good choices too.
- Drink at regular intervals (instead of when you feel thirsty)
- Keep water convenient
- Monitor your hydration
- Choose the right fluids
Now, pull on your woolies, hydrate, and let's go play!