Running and keeping hydrated

August 4, 2012 - 9:23 pm 1 Comment

When I decided to write up a post about running and keeping hydrated I thought it would be pretty straight forward, drink lots of water, but searching for articles online I found the research on sports and hydration is not that clear cut. I chose to link to some good articles and summarize what I thought was relevant for distance runners.

This first article is from the British Medical Journal. They took six different health claims made by sports drinks manufacturers and even health websites and evaluated the evidence behind those claims. I believe what they did is called a meta analysis. This means looking at many different studies done and analyzing the combined results to see what conclusions can be accurately be drawn.

Mythbusting sports and exercise products

BMJ 2012; 345 doi: 10.1136/bmj.e4848 (Published 19 July 2012)

 

The first of the claims assessed actually surprised me. It has to do with the idea of using your urine color as a measure of your hydration level. I myself have heard or read this quite a few places and as a runner tried to drink enough to keep my urine a specific color. First of all, it seems the quality of the studies done on urine color aren’t really up to par.

The article states:

“We found eight low quality studies published with no systematic reviews. As there is no objective measure of hydration, all of these studies compared urine colour to surrogate markers: none directly investigated the correlation between urine colour and performance or the correlation between urine colour and thirst.”

Further, three of the studies recommended color of urine, but only as an estimation, three studies concluded that urine color is not accurate enough to use and the remaining two only recommended using the first bladder void of the morning as a hydration indicator or using urine along with other hydration markers. Basically, more studies are really needed before using urine color can be recommended. The article even goes far enough to warn against the potential risks of drinking to get a pale colored urine can lead to over hydration or hyponatraemia (too low sodium levels in blood).

That last line actually led quite well into the next claim the investigated: drink before your thirsty. This advice comes directly from the sports drink manufacturers. (yea, because there’s no conflict of interest there!)

According to the article, Gatorade’s website states that “(your brain) doesn’t know when your body is thirsty. You need to drink during exercise before you feel thirsty in order to get enough fluids in your body to maintain your performance level”  I had trouble finding this on their site, but I know I’ve followed similar advice myself, drinking lots of water the day before a big run. I’m not sure where Gatorade is getting this idea, that your body doesn’t know when it’s thirsty. The article states the exact mechanism by which your brain knows it’s thirsty. “Osmoreceptors in the hypothalamus detect dehydration and signal other parts of the brain to stimulate the sensation of thirst.”

I think the most important part of this article that directly relates to me and all you other runners out there is this next quote:

“Although we could not find a report in the medical literature of dehydration being a direct cause of death in marathon runners, we did find overhydration was responsible for several deaths.24 25 By following advice to “drink before thirst,” many athletes are drinking too much, which does not help performance and puts them at risk. A recent study of 88 participants in the London marathon found that 11 (12.5%) developed asymptomatic hyponatraemia.26″

The rest of the article covered some interesting topics and I highly recommend reading it. (the bolded title above is a direct link). What I got from this article was drink according to thirst. For me, that means having water with me on long runs and any runs in hot weather. I found a running water bottle I love! (here’s a link to it on Amazon) It’s got a nice pocket for my keys, gel packs and blister band-aids. I much prefer to run holding my bottle in my hand rather than carrying bottles on my waist or a camelbak. I know this is highly individual and there are tons of styles to choose from.

 

This second article I found from the wikipedia article on marathons.  It comes from the Association of International Marathons and Distance Races.  Although they present the information simply and don’t quote direct sources, the advice confirms some of what the other article I linked to stated.  It’s called Guidelines for fluid replacement for runners and walkers.  I highly recommend checking it out since this post is already super long so I won’t summarize it in too much detail here.  Simply speaking, drink a sports drink with carbs and electrolytes for long workouts (30+ minutes by their standards) and drink to thirst to help avoid over hydrating.  They have more specific guidelines for fluid replacement for marathon runners based on time/pace and also give instructions for using body weight to determine more individualized fluid replacement strategies.

The last thing I wanted to mention relates to exercising for weight loss.  My one concern with taking sports drinks during long workouts is the added calories.  A big reason I really like long weekend runs is they burn a ton of calories, especially fat.  I was thinking since my long runs right now are not for performance, but for weight loss I might compromise a bit.  I always bring water on my long runs but if they go over an hour, I’ll bring a sports gel with me.  (the ones I use have the requisite carbs and electrolytes and I eat them with water.)  Plus, as long as I keep track of how many calories I consume in a sports drink and use that in my weight loss calculations, weight loss should still be achievable while staying properly hydrated.

One Response to “Running and keeping hydrated”

  1. Carrie Weiler Says:

    Love it, Jess!! You are incredible. Thanks for keeping us posted on your training! And good luck!!

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