It is often said that a human being can last up to three weeks without ingesting a single food, but will not see more than three or four sunrises if he stops drinking water. This is a half-truth, not only because cases have been reported of people surviving up to twelve days without water, but also because it is perfectly possible to die in a single day due to dehydration problems.
Leaving aside the records, all of us who practice mountain and/or outdoor sports know the importance of hydration. We know that we must drink water before, during and after the activity, and we know it because we have been told or read it a thousand times. And yet, a study carried out in four mountain refuges in Aragon in 2012* showed that in practice we all walk, at the very least, poorly hydrated. But be careful, because the consequences of being “short of water” can be quite serious.
We are homeothermic animals, which means that our organism is capable of maintaining a stable internal temperature whether we are strolling around Qatar at midday or going on a Christmas tour of Moscow. If you stop to think about it, it is quite remarkable that when we are healthy our temperature does not vary by more than 0.6°C no matter what; but of course, on the other side of the coin is the disturbing fact that it only takes a few degrees too high or too low to kill us. Between the ideal temperature and those fatal extremes there is a progressive decline of faculties which is, it seems, where we tend to move around the mountain more often than we should.
What Water Is For?
Water is a basic element for that physiological feat we just talked about, which we call thermoregulation. When we carry out a demanding physical activity, our body is subjected to a rhythm of functioning that, apart from generating the movement we are interested in (reaching the summit, crossing the finish line, completing the route…), also generates heat. This excess body heat is released by the body through evaporation; in other words, through sweating.
So, first of all and paradoxically, water is essential because we need to get rid of it. We use it to cool the body and the moment we lack it, our body temperature will begin to rise, bringing us dangerously close to hyperthermia.
This is not the only reason why we should always be well hydrated. Water also acts as a lubricant for almost all bodily functions. Lack of fluid in the body has a wide variety of consequences for the organism:
- The blood thickens, oxygenating the muscles worse, resulting in fatigue, cramps and injuries.
- The joints, less hydrated, suffer greater wear and tear, so that overloads and joint injuries become a common danger.
- Attention decreases, fatigue, disorientation and dizziness appear. In delicate activities, such as climbing or walking along a ridge, the lack of water can lead to very dangerous absent-mindedness.
- The throat dries out, causing the cold, dry air of the high mountain to damage our breathing.
- The eyes dry out, because no matter how much we blink, we will not be lubricating them properly.
And a long etcetera of consequences, all of them bad.
Hydration In Winter
All of the above and our own experience may lead us to think that hydration is essential in summer, but not so much in winter. After all, in winter it’s all about staying warm, so there’s no need to release heat, right? Big mistake. Interestingly, hydration is a more complicated issue in winter activities than in summer activities. And it is for several reasons:
For starters, the red light on the body’s dashboard, that alarm that warns us that we are running low on water and that we call thirst, is a mechanism that works worse at low temperatures. The cold causes vasoconstriction, which is a kind of general withdrawal of the organism towards itself. By “closing the windows” and concentrating on the central circulatory system, the body stops receiving the peripheral signals of volume loss associated with lack of water and does not warn us of what is happening. That we are less thirsty when it is cold is not a sensation, it is a reality.
But that does not mean we are not losing water. Physical activity still generates excessive heat that needs to be removed. In winter, much of the heat is dissipated by losing moisture through respiration. And since the altitude makes us breathe faster, dehydration in winter mountain activities is accelerated.
As for sweating, we sweat in winter too, of course we do. It’s just that, as sweat evaporates more quickly when the air is cold and dry, we don’t feel it as much as in summer because the shirt doesn’t stick to our backs in the same way. Once again, the alerts fail.
So, although it is true that in summer dehydration occurs at a faster rate due to the outside temperatures, in winter things get more complicated because it arrives without us noticing it.
How We Should Hydrate
The rate at which we should hydrate depends on many factors: outside temperature and humidity, age, activity level, altitude… so it is impossible to establish a rule.
The best thing to do is to try to make drinking water an unconscious habit before, during and after the activity. It is well known that when thirst makes an appearance, it is because we have already exceeded certain undesirable limits, so the ideal is to drink every few minutes out of habit, rather than out of necessity.
However, we will not make hydration a reflex action if, in order to do so, we have to stop our activity, take off our backpack, dive into it looking for the water bottle, drink, and then get going again. Too often, in fact, we delay the act of drinking water, even when we are thirsty, because we are too lazy to go through the whole ritual.
That’s why hydration backpacks are a highly recommended item. A hydration backpack allows us to drink without having to stop walking, pedaling, or whatever we are doing. It’s good to have a water bottle, because at stops we will appreciate being able to drink in sips, without having to suck, but during the march that small rubber tube will allow us to replenish that wonderful liquid that allows our body to remain always well oiled, well attentive and at the same temperature, no matter what happens.