Recreational runners may be getting too much hydration during races, according to a study conducted by Loyola University Health System. A survey of 197 runners found that 36.5 percent of runners drink based on a schedule or to maintain weight, and 8.9 percent of runners drink as much as possible.
Advertisements for sports beverages in past decades may have fed into misconceptions about the amount of fluid needed to prevent dehydration and encouraged athletes to drink as much as possible. Current guidelines from the International Marathon Medical Directors Association recommend that athletes drink only when thirsty.
The study also found that 29.6 percent of runners believed they needed to take in extra salt during a run to replace sodium lost through perspiration, and that nearly half of runners consume sports drinks because they believe they will prevent low sodium.
But drinking too much liquid - water or sports beverages - during a run can actually cause low sodium levels. This can lead to a condition called hyponatremia, which has been linked to at least 12 deaths in recent years. A 2004 study by The New England Journal of Medicine found that 13 percent of participants in the 2002 Boston Marathon suffered from low sodium levels after the race, likely caused by overhydrating.
The study is just one of many in recent years that challenge common beliefs among runners. A 2010 study found that stretching before a run causes no harm but offers no obvious benefit to runners.