Pre- and Post-Race Hydration Status in Hyponatremic and Non-Hyponatremic Ultra-Endurance Athletes We have studied the hydration state of 113 extreme duty athletes before and after a competition. If one compares people with and people without hyponatemia after the competition, there was no difference in the blood in the blood before the competition and the specific gravity in the urine and the body weight before and after load.
Surprisingly, both people with and people without hyponatremia after the burden were already very well hydrogenated before the competition. All other details can be found under https://pubmed.ncbi.nlm.nih.gov/27188470/