I should add here that it can be really dangerous to get too low on electrolytes! In 1994 hubby and I went for a bike ride and - for a bunch of reasons - hubby's electrolyte balance got all screwed up and it sent his heart into arrythmia. He lived with it for 8 days before collapsing and was put in the hospital (we were living in Ethiopia at the time). the Ethiopian doctors knew exactly what needed to be done, but they refused to treat him due to the risk of him dying and they had no backup, so we had to get an air ambulance to Israel - at a cost of $90,000!!!!!

So - if you are sweating profusely for extended periods of time you need to make sure you drink! Drink! Drink!