Should You Drink Extra Fluid 24 Hours Before a Marathon?

The first published finding regarded runners' sodium levels, which Mohseni said were found to be lower after the race in slower runners, who take longer to finish.  That means slower runners have more time to drink more water along the route, where volunteers are giving water out at every mile, Mohseni said.

Another aspect of the study focused on whether increased fluid intake in the 24 hours prior to a marathon affects the body. The answer is "no, in our race it did not," Mohseni said.  -jacksonville.com
 
Michael Mohseni is a Mayo Clinic emergency room physician involved in the Runner's Science program.
 
MY COMMENT:  Neither finding here is surprising, although very few marathoners, even at an elite level, are aware that chugging extra water for 24 hours prior to a race apparently has little or no effect on their race day performance (unless of course they are dehydrated to begin with).  Humans are not camels! 
 
Sherry Mahoney, Mayo Clinic Director of Nutrition, recommends about 4 swallows (or ounces) of liquid every 20 minutes.