wanderingherb that's some really cool information you have there! Thank you for that! I would definitely be sharing that to my students the next time I have a lecture about fluids and electrolytes.
One thing I know about hydration is that when you are working out, like, sweating so much, you need to replace your electrolytes too and not rely on water only. I had a friend who only drank plain water during her workouts, she collapsed one day and we brought her to the hospital. The doctor said she collapsed because of dilutional hyponatremia, meaning, the concentration of sodium and other electrolytes in her body were diluted by all the water she drank and this sends a signal to the brain that there is too little of these electrolytes.
So make sure when you hydrate during great-sweat days, don't forget the electrolytes in your drink!