The above is my paraphrasing the BMJ report, and not my interpretation necessarily. I will note that I am likely one of the very few scientists in the field of exercise physiology and hydration research with no conflicts of interests. Apart from my doctoral research in the mid 1990s being funded by contracts with the Canadian Forces, I have had no direct or indirect interactions with any companies related to sports drinks.
I also know well many of the scientists involved on both sides of the argument as friends and colleagues for many years. Therefore, I think I'm well placed to give a hopefully objective perspective to this controversial field (feel free to comment otherwise and provide your own insight).
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Conflicts of Interests
The field of exercise physiology is actually a very small world and the funding pales in comparison to big medical or pharmaceutical fields. Therefore, it is very hard to find scientists who have no conflicts of interests to create an "independent" oversight group. Knowing many of these scientists in and out of the lab, I certainly do not buy into a conspiracy theory approach that there is deliberate misrepresentation going on.
I do agree with the charge about large policy making bodies, like ACSM, making position statements about hydration while being directly supported by sports drink companies. If nothing else, the optics are very, very murky this way.
Summary: a draw on this one. I believe in the scientists on both sides of the issue, but I have a harder time trusting large organizations.
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Dehydration Versus Hyponatremia
I think this issue is wracked by imprecise arguments, with me arguing one idea, you arguing a separate idea, and both of us incorrectly thinking we're arguing the same idea. Let's look at what I see:
- Would I err on the side of dehydration or hyponatremia? This is simple—both are not desired and should be avoided!
- Do indeed listen to your thirst. It is an important psychophysiological signal to guide your behavior. This is exactly analogous to using Ratings of Perceived Exertion (RPE) as a gauge for your workload. Is it perfectly accurate? Not nearly compared to direct measurement of power output. However, can it be trained to be more accurate and reliable? Absolutely. Listen to your thirst, use it with pre/post exercise weighing to get an idea of fluid loss, and drink a reasonable amount to avoid too much fluid loss or too much drinking.
- How much is too much loss? Keep track of how you perform and feel with different levels of drinking during exercise, and keep track of your weight over multiple days to make sure you can train yourself to drink enough to recover day-to-day.
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