How Much Should You Be Drinking?
The answer to this question of how much to drink is both staggeringly complicated, and unbelievably simple.
A little history on hydration recommendations…
In 1996 the American College of Sports Medicine (ACSM) released their Position Stand: Exercise and Fluid Replacement. This document recommended 600 – 1200 ml per hour of fluids. This seems a little high nowadays.
In the subsequent years, there were a few tragic deaths due to hyponatremia (in short, over drinking while exercising). This hadn’t been such a problem in earlier years of endurance sport, so a few alarm bells went off.
The International Marathon Medical Directors Association (IMMDA) released their own guidance in 2002 that had a recommendation to 400 – 800 ml per hour. This work was led by a chap who had a lot of expertise in hyponatremia (over drinking).
In 2005 the ACSM had another go at it, and released their Roundtable on Hydration and Physical Activity: Consensus Statements. This document doesn’t give a figure at all for how much you should drink per hour. Instead, they say you should aim to keep weight loss to less than 2%, and make sure you don’t drink so much that you put on weight.
Of course, the IMMDA had another crack at coming up with something simple and more or less said that in modern marathons, there are so many different body weights, that 400-800 ml per hour might not be suitable. The advice, and we’re not kidding here, is just drink if you’re thirsty and not so much you are peeing too much. Genius.
We’ve taken a little liberty to paraphrase some of this info above to try and keep it simple. These are highly complicated papers on a highly complicated and controversial topic. We recommend you download these documents and read them yourselves. They are all freely available on the internet. They also give great info on carb requirements, cramping, recovery and many other topics. They really are essential reading for anyone pushing their limits.
At R-Line, we’re big fans of the “drink if you’re thirsty” philosophy as a starting point for any strategy.