I think you're generally right BUT I overhydrated in January during my 1st marathon. I was quite hyponatremic (low body salt = water intoxication) and confused when I finished. It was a bit scary. The saving grace is that I took Endurolytes during the race which lessened the water intoxication (and I mostly drank PowerAde instead of water) and my husband and I are both doctors and figured out what had happened before I needed serious medical help. Water intoxication can be serious or even fatal and I try to share my experience so others can avoid it!
I got very overheated during the race and, in my inexperience, misinterpreted the heat exhaustion as dehydration. I drank 2-3 cups of PowerAde at each water station starting around mile 18. I've subsequently learned to dump water on my head if it gets warm and only take one cup of PowerAde at each station.
Given how many novice runners are at the Disney events (I include myself in that!), I think it would be easy for others to make the same mistake. I do seem to have relatively high fluid/salt requirements so I do drink one cup at each station but I stick to electrolyte containing fluid and take my salt tablets.
Amanda
Amanda, I am the same way. I need to keep track of the electrolytes or I get way underground drinking to my thirst when running. I sweat a lot when running (but not much at all in everyday life) and my sweat is super salty. I need the salt tablets to keep up. I think that it is safer to be a little dehydrated than hyponatremic.
My last hot, humid race was the ToT race. I dropped my salt pills by accident at the one hour mark after taking one, and even with Powerade at every station, I finished the race hyponatremic. I was out for 2.5 hours and drenched in sweat. When I finished I was sloshy in my belly, weird leg cramps, and my hands were a bit swollen (fluid going into the third space to rectify plasma hyponatremia for those who wonder how this is a symptom) - all signs for me. I also had a bit of heat exhaustion going on too - foggy brain, headache, and nausea. I corrected them both and woke up feeling great.
Now I stash salt pills in more than one place for races, dump water on my head to keep cool, and really pay attention to the small signs that I am getting out of balance and correct as I go. I juggle salt pills and fuel, with water and electrolyte drink. Kinda satisfying to fix myself as I run and give myself the ability to carry on.
Also, not directed at you Amanda, you can be dehydrated and still be drinking if you are hyponatremic. That water will stay in your belly, or go to your intestines or other third space areas, and not be processed by your kidneys if your blood chemistry is out of whack. Your body will prioritize electrolyte balance over hydration, to a certain point (and then your body will prioritize blood volume over blood chemistry when you get dangerously dehyrated). It isn't as easy as just drinking at every station for everyone. If it were, no one would collapse or need med help - and in these weather-challenging races it seems that many people fall ill in ways that could otherwise be prevented. Anyway, this is my understanding of the subject, YMMV.
My solution: drink often but not a lot at any one point, and take electrolyte tablets. I may still get out of whack, but not nearly as much as I would otherwise, and likely well within a buffer of my body's ability to self-regulate.
The symptoms of hyponatremia are much more subtle for me than dehydration (primarily very thirsty!) so I just make a schedule for that day's run depending on the weather and distance for fluid, fuel and electrolytes and take stuff on schedule. It has worked really well for training in very hot and humid summer weather. As a slow runner out for a long time on long runs I feel that I have to be especially careful. A summer 20k run means a 3 hour period of sweating profusely for me.
