Water You Mean, I’m Overhydrated?


Science is interesting in that new ideas or re-evaluation of old adages are often ignored and the same debunked ideas are recycled and spouted as fact. The most extreme example of this outside of the world of athletics relates to the other half of my life.

In an article in The Lancet from 1998, a researcher made a correlation between vaccines and autism. Not only has that claim been thoroughly debunked, but the researcher was barred from practicing medicine in the UK for falsifying data and the article has since been retracted. However, the roots of that nonsense study run deep enough that pseudo-celebrities took up the cry and now parents too young and ill-informed to remember what Polio is are choosing not to vaccinate their kids, which should probably be considered a form of child abuse, either for their own child or for the children they come into contact with, in my opinion.

On a lighter and more blog-related note, what is the proper amount of water that a person should consume on a daily basis in order to neither over- nor under-hydrate? The answer most sources provide is eight glasses of eight ounces. That’s the “apple a day” slogan, if you will, for proper hydration. However, research suggests such a claim is not really based on any real value. This article explains the basis of that myth, among other gems like the 10% brain thing that people love to throw out as fact.

Where does that information leave endurance athletes, though? They actually have their own potential myths to deal with. Dr. Tim Noakes has worked hard to turn the tide against the marketing and previous research (his included) that focuses on overhydration. The adages to drink as much as you can before, during, and after runs, rides, and other exercise activities seem to be less than ideal notions to adhere to when trying to maintain proper hydration.

We see ads and hear the “8 glasses a day” spiel over and over again so often that when you are riding, especially with a hydration pack, this information can cause you to drink as often as possible and potentially drink too much.

The biggest risk in that is inducing hyponatremia, which can lead to death. This is quite rare, but can happen. Noakes’ suggestion is to stop pretending we need to consume more liquid than our bodies are calling for. Do not drink when you are not thirsty; your body will tell you when to drink. If you do it at that time, you will never get dehydrated and you will never get close to over-hydrated.

A meta-analysis of properly controlled studies assessing liquid consumption on the ability to perform in a time trial event found that the 2.2% average weight loss in the dehydrated group did not result in lower time trial power output compared to the 0.4% weight loss in the hydrated group. One study in that meta-analysis that looked at cycling found that performance is only really disrupted if no fluid replacement is provided; dehydration itself does not impede performance. For cycling, sports drink consumption is important not just for hydration but for carb intake, so cutting back on fluid intake could be detrimental if you are not factoring in the loss of carbs.

All of this translates to paying attention to how much you drink during a long ride and to not just keep drinking and drinking and drinking with no regard for how much fluid you are losing via sweat. So if I use a hydration pack instead of just a water bottle, which I plan to do on my July tour, I have to make sure to not just drink and drink and drink and instead schedule out my intake for when I will need it the most.


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