Drink According to Thirst During a Marathon

The three groups, by time, and their weight loss:

Those who finished under three hours averaged a 3.1% body weight loss.
Those who finished between three and four hours lost 2.5%.
Those who took more than four hours to finish lost 1.8%.-Weight Loss During Marathon Improves Running Time

MY COMMENT: Ok, this is exactly the opposite of you would expect, but Tim Noakes, an expert on hydration and heat related problems, has been on the trail of optimal hydration during marathon and ultra events for several years and knows his data.

What I'm wondering about is what the runners weighed just prior to the start of this marathon compared to their normal weight (I assume when you are optimally hydrated and carb. loaded you are a 2-3 pounds heavy, which makes this finding even more amazing! I'd also like to know the average body weight of runners in each group- my guess is the faster runners were lighter, yet they lost the highest percentage of total weight. (note: I'm too cheap to pay for access to the orginal article published in the British J of Sports Med)

Noakes is clear on this: "Drinking either more or less than to thirst impairs exercise performance".

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.

How Much Water?

With water, a lot of that is going to depend on the weather. The big thing is hydrating the day before the race. I will have 20 ounces of water right when I get up in the morning the day before, and I’ll drink throughout the day. Then three hours before the start, I will put down 20 ounces of water. -Ryan Hall, NYTimes interview



MY COMMENT: Not bad advice to hydrate the day prior, then 3 hours before the start gives you plenty of time to hit the bathroom before the race starts.

How Much Do You Drink?

About an hour before the workout you should have about 20 ounces of liquid.

-Leslie Bonci quoted in a NY Times article.

MY COMMENT: Unless you are preparing for a marathon or getting ready for a very long (2 hours or longer) training run, I don't know anybody who really does this.

Read the full article, then see my comments below:

First, I’d be very uncomfortable drinking 20 oz of water one hour prior to exercise, and that much certainly isn’t necessary for a 30 minute workout. Second, I’d be curious what the definition of “gulping” and what frequency is recommended. Better advice would be to weigh yourself before and after every workout and using trial and error target not losing more than 3% of your body weight. Some experts agree that blanket guidelines for hydration are not a good idea- this much water for a 100 lb female with a low sweat rate running on a cool day in fact may be very dangerous. Third, I’d be careful what type of carbohydrate you eat 1 hour prior to exercise. If I eat something high on the glycemic index prior to exercise often times my blood sugar drops so low after start my run that I experience light-headedness

Are Cramps Related to Overdrinking?

The pace didn’t feel bad at all and I had the energy,” said Ritzenhein, who completed his fourth marathon. “I felt like everything was going great until 20 miles. My calves and hamstrings started twitching every couple of seconds or so and I felt like they were going to cramp up. I would shift my weight back and waddle along at about 5:15 pace. If I went any faster I thought they would go again.”

Ritzenhein took three salt tablets during the last 10K to help alleviate the problem. “I didn’t think I was dehydrated,” he said. “My fitness felt great. The last 10K wasn’t even hard.” -universal sports



I met with a nutritionist on it and I think there are definitely some things that I can change, some overhydration problems that I've done in the weeks and days leading up to the race. You wash out the sodium and things like that that are necessary. It's a matter of drinking too much straight water until a couple of days beforehand. It takes a few days for your body to catch up. If you drink only water for two weeks and then you switch to sports drinks a couple of days before the race, it still doesn't have the desired effect runnersworld.

-comments by Dathan Ritzenhein on a mistake he believes he made by drinking too much water in the days leading up to the London Marathon where he cramped and still ran 2 hr 10. (Ritz also experienced muscle cramps in the Olympic marathon)

MY COMMENT: I wonder how much water he was actually drinking in the days leading up to those races? Here is another reason not to overdrink before a big race.