Heading into this Sunday's Chicago Marathon, debate continues over how much water runners should drink before and during the race.
Discussion was sparked by the death of a North Narolina runner during last year's race.
An autopsy shows William Caviness might not have had enough to drink when he collapsed and died just short of the finish line.
Other medical experts say it's more likely Caviness had an undetected, pre-existing heart condition.
They say the dangers of over-hydrating far outweigh the dangers of not drinking enough
The International Marathon Medical Directors Association recommends drinking only when thirsty.