Ever since I started running, all I know is that I need to drink a sh*t ton of electrolytes. But I would like to understand why on a physiological level.
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You need two things: blood volume and blood saltiness.
If your blood saltiness goes outside of a fairly narrow range, very bad things happen to you.
If your blood is not salty enough (often because you’ve sweated a ton), your kidneys will dump water out of your blood, to bring the salt concentration back up.
However, this can end up lowering the total *volume* of blood in your body down below optimal levels, making you feel thirsty.
So you drink more water, and pee it right back out again because yikes not salty enough.
And because your kidneys aren’t perfect machines, they always leak *some* salt into your urine, reducing your total salt level even more.
Rinse (out) and repeat.
This is no fun for anyone involved.
In order to fix it, you need to consume some salt (and optionally some other salt-like chemicals) so your kidneys will let you hold onto the water you take in.
If you take in too much salt, it’s less of an issue, as you can just guzzle water to dilute yourself, and your kidneys will gradually let the excess volume out along with some of the salt. It takes longer but it gets there without too much intervention.
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