Watch the water
Excessive fluid intake during exercise can be dangerous, and potentially fatal. University of South Africa researchers warn that consuming a lot of water during exercise can cause a condition called hyponatremic encephalopathy, where a lack of salt in the blood causes the brain to swell. To-date, 250 cases of this condition have been reported and at least 7 people killed ? including a 28-year old woman runner in the 2002 Boston Marathon. To quench thirst, limit water intake to 400-800 ml (14-28 fluid ounces) per hour of physical activity