Exercise Hydration

Military training protocols recommend a maximum fluid intake of 1 to 1.5 liters per hour during intense exercise. Blood tests at the 2005 Boston Marathon finish line found that 13% of all finishers had clinically detectable hyponatremia. Endurance athletes are the highest-risk population for hyponatremia due to the combination of sodium loss from sustained sweating and dilution from high plain water intake. During sustained physical activity, water intake should always be matched with salt intake rather than drinking plain water in isolation.