Everybody is telling us to drink lots of water and to stay hydrated, but how much do we actually need to drink to prevent dehydration? In this post I give my understanding of staying hydrated.
Dehydration is when the body loses an excessive amount of water, resulting in a disruption of metabolic pathways. Generally speaking the body can tolerate a slight loss of water, however when this loss is extremely excessive the athlete experiences symptoms such as fatigue and dizziness.
One common myth, or misconception is that you should drink before you get thirsty. The logic behind this misconception was that being thirsty was a sign that your body was becoming dehydrated. While this is true, it is not too late to drink when your body reaches this stage, adequate water consumption can successfully rehydrate your body. However, drinking before you get thirsty could result in athletes consuming too much water.
acute dehydration is not an issue, and even in extreme scenarios the body has measures to prevent severe dehydration. These measures cause the body to shut down certain processes, stopping the physical exertion which is causing the dehydration. This is clearly a drastic negative consequence for performance athletes, which is why avoiding dehydration is recommended. Consequently, many recommend drinking plenty of water, but this advice is not sound.
If we examine our bodies on a cellular level, an aqueous environment is. required for our cells to survive, and our exchange surfaces need to be moist to facilitate exchange. Our bodies require water to maintain a suitable environment for our cells to regulate their environment and perform their function. From this information it appears as though drinking lots of water is a good thing, right?
Wrong. Consuming excessive amounts of water not only dilute the nutrients in your body, but can also effect the efficiency of your cells, and hence your performance. Our cells are microscopically small to maintain a high SA:V (surface area to volume ratio). Having a high surface area to volume ratio is beneficial as there is a large surface area for exchange to occur across and minimal volume, allowing the concentration to change faster.
When too much water is present in the extracellular environment the process of osmosis causes a net movement of water into the cell. This not only causes a dilution of nutrients such as sodium, but also causes the cells to expand. A larger cell would have a lower SA:V, resulting in a decrease in the rate of exchange. This decrease in the rate of exchange slows the cells intake of glucose and other nutrients, which could have a negative impact on an athlete's performance. It also reduces the ability of our bodies to remove this excess water.
In extreme scenarios, our brain cells may expand excessively, causing the brain to swell, resulting in the death of the athlete. There are a few documented cases where athletes die due to excessive water consumption. There are also many documented cases of athletes collapsing due to dehydration, and the media has even (incorrectly) attributed some deaths to dehydration. Dehydration is an issue, but the bigger issue is drinking too much water. Drinking too little will stop you. However, drinking too much may kill you.
It may sound like I'm trying to discourage you from drinking. I'm not, I'm merely recommending that you perhaps examine how much you drink during your rides. If you're someone who has a habit of drinking every 5-15 minutes or believe that drinking before you get thirsty will improve your performance I implore you to try drinking less. Once you become used to this routine you may notice performance benefits.
What about isotonic sports drinks? These drinks have salts and other nutrients in them, in a similar concentration to what's present in your extracellular fluid (if they are prepared as recommended). My logic tells me that they should prevent nutrients from being diluted. however I would still caution drinking before you are thirsty. It's interesting to note that these companies recommend consuming 250ml of their product every 15-20 minutes during sustained and strenuous exercise. Drinking 750ml-1000ml per hour seems excessive to me, but perhaps that's because a 20 minute TT effort is more strenuous than a 60 minute TT effort.
I always like to consider the other side in arguments as well. There are plenty of articles suggesting that we should be drinking to offset sweat loss. In terms of sweat loss, I believe we "offset" this during our recovery periods in between sessions. Some also suggest that thirst is an unreliable indicator, particularly in older adults. Whatever your beliefs are, I believe you should examine them critically. My final note of caution is to always consider who the author is, and why they are writing that article.
Thanks for reading!