Popular hydration options among runners and endurance athletes include water and carbohydrate-electrolyte solutions, also known as sports drinks. Sports drink manufacturers, in an effort to sell more product, have convinced a large number of athletes — including accomplished runners — that the key to avoiding medical problems during exercise and racing is to drink as much as possible.

According to new research published in the British Journal of Sports Medicine [1], many runners have erroneous beliefs about their hydration needs, and thus overhydrate by drinking according to a schedule, or drinking “as much as possible.” This increases the risk of exercise-associated hyponatremia, an electrolyte disturbance in which the sodium concentration in the serum is lower than normal. Hyponatremia can cause nausea and vomiting, headache, confusion, fatigue, muscle weakness, cramps, seizures, decreased consciousness and/or coma. With events from community 10K races all the way up to marathons and ultramarathons increasing in popularity among non-elite athletes, understanding public belief about hydration and subsequent hydration behavior is an important public health topic.