Having just found out about this condition i feel the need to explain a little bit on the life threatening disorder. Ever been on a PT lesson and constanly told to drink plenty of water before hand, during and after well i would reconsider doing so. Hearing storys of people dropping down dead on CFT'S and the fact my girlfriend has this condition i started to look into it in more depth. Basicly if you drink shitloads of water during excersise you could collapse if not slip into a coma or even die. Water dilutes the sodium in your blood and vacates your body either through your urine or sweat glands hense the white marks on your boots when you have sweaty feet. Your body can not function correctly without the right ballance of water and sodium levels thus bringing your blood pressure dangerously low and causing water to sit in your brain with your blood. Everytime my g/f goes for a pee she collapses because of the sudden loss of sodium that has been diluted. Advise by various websites is to drink something like lukozade hydro active water this has worked wonders for my g/f she is now completely back to normal. This is not an advertisment it is serious stuff which people need to know hope it is usefull. For more info search google for hyponatremia.