"Drink as much as you can, even before you feel thirsty." That's been the mantra to athletes and coaches for the past three decades, and bottled water and sports drinks have flourished into billion-dollar industries in the same short time. The problem is that an overhydrated athlete is at a performance disadvantage and at risk of exercise-associated hyponatremia (EAH)--a potentially fatal condition. Dr. Tim Noakes takes you inside the science of athlete...