By Coach Adolfo Salgueiro

The basic concepts on hydration have moved like a pendulum through the last century of athletics in general but running in particular. While the earlier runners of the Boston Marathon took it as a matter of pride not to consume water, in later years the thesis of never been able to consume too much came en vogue and was disproven. Now days, we are in the “drink to thirst” phase. The truth is that there is not a one-size-fits-all approach to the matter. What worked for Bill Rodgers in the 1970s, does not work for Eliud Kipchoge, setting the world record and does not necessarily work for you, right now.

When it comes to hydration, extremes do not work. Not taking any liquids during a marathon is a recipe for disaster that doesn’t require much explanation. The “more is better” can lead to the life-threatening condition known as hyponatremia, whose explanation is beyond the scope of this blogpost.

It is important to understand that if you are running 3-6 miles, 3-4 times a week, your body may have everything it needs to cope with your hydration needs. There should be no need for a hydration strategy per se unless you are running in an oppressively hot and humid environment. A quick 5K around my block is not the same as 5K in the Sahara at noon. But once you are getting up on mileage, or start training for a longer effort, then it becomes imperative that you do something about your hydration needs.

“Hydration is a balancing act—says Andy Blow, British Sports Scientist and founder of Precision Hydration—One thing we can all agree is that once you hit a level of under-hydration, where you lose enough fluids and electrolytes, at some point you will reach serious problems, such as reduced cardiovascular function because your blood gets thicker and thicker as you get more and more dehydrated. Then you dissipate heat less well, you overheat and from there you get into a downward spiral.”

Finding out where in the spectrum you fit; how much you need to drink, how often and what electrolytes you need to replace is your responsibility as a runner. Sure, a coach can and will assist you, but only if you feed him the right data, which is your duty.

Hydration Specialist and Sports Scientist Andy Blow

An easy home test to figure out how much you sweat on a specific setting, let’s say on a summer long run; is to weigh yourself naked right before you leave. Run for an hour without consuming anything. As soon as you get home, get naked, wipe yourself off and weigh yourself, again. The difference in weight is how much sweat you lost in an hour. Each gram lost is equivalent to about 1 milliliter of water, as there are other contents in your sweat (in the Imperial measure system, each tenth of a pound is equivalent to 1.6 Fl Oz). This is your sweat rate and the approximate amount of water you need to replace as you run in similar conditions. Yes, it is that simple.

As personal as the sweat rate is, the contents of your sweat are equally individual. You need to know what is in your sweat so you can replace it. If you are caked in salt once the sweat evaporates, then you are losing a lot of salt, 40% of which is sodium, a key electrolyte. So, if this is you, you need to go above the set guidelines for salt intake, as these are not for athletes but for normal, inactive people.

According to Blow, the best approach for hydration on shorter runs (90 minutes or less) is not to have a plan but to drink to thirst. For longer runs, like a 20-miler on a hot summer day, you need to consume not only water but also sodium to compensate what is being secreted and keep your stores as topped off as possible.

There is so much more about hydration. Not all of it can be addressed in just one post. Tim Noakes, the world renowned South African sports physiologist, wrote “Waterlogged”, a book about the topic which is 448 pages long. If you want to dig deeper into the subject, this is my recommended source.