Hydration Evolution: Where Are We Today? Should You Have a Plan?

The good news: all my workout clothes are laying on the driveway asphalt drying in the warm sun.  Now the bad news: I just looked outside and it's raining!  (Surely something like this has happened to you.)

"Custom" race hydration plan.

If you take away from today's blog that there's no single right way to control one's race/training hydration needs that covers all circumstances, you'll get the point.  It's so easy to have some quick, catchy phrase that gets picked up in 140 (or 280) character messages, or quickie soundbite.  Paraphrasing H.L.Mencken, "for every complex problem, there is an answer that is neat, simple and wrong."

Managing fluid, and to a much lesser degree electrolyte requirements, is like solving an equation with ever-changing variables.  But old habits are hard to break.  Let's look at my swim group as a starting point.  It wasn't that many years ago that we were instructed to "drink early and drink often" during work outs.  But that also has been taken to the extreme as even if we're only in the pool for an hour, well over half the group stops after a pull set or 400 of kicking for "needed" re-hydration.  I wonder if I've ever taken a water bottle to the pool and I swim more than most.  Lots more.

This is not a tutorial on all that's known about over-hydration, hyponatremia and death, but suffice it to say that particularly in the marathon community, slower runners on cooler days who consume more fluids than the body requires actually gain weight as the race progresses.  Basically this is a bad idea.  This fluid overload can dilute the body's serum sodium, which in extreme cases, can lead to seizures and death.  On the other side of that same coin, those who champion only allowing the body's thirst regulatory mechanisms to guide replacement can correctly, although perhaps harshly, point out that "you don't usually die from dehydration."

"For any serious athlete who's worked very hard leading up to an event and wants to perform, I would go into that event with a plan."  Asker Jeukendrup  

Understand that Jeukendrup notes that in longer races like the marathon and 70.3 racing, drinking early may be of significant benefit, not waiting till one is thirsty.  In the early part of a race, your gut is still working well enough to absorb fluid and nutrients where later in the event, when you may be more thirsty, the stomach may be a much less willing accomplice.

From an area ultra runner.  "The marathoners/trail-morons that I hang with are almost all in the camp that you need to be drinking long before thirst.  If you actually get thirsty during a race then you're probably already screwed... and you can quote me on that."

The metric that I found and have liked for my training/long runs is 2 ounces a mile.  So over the course of an hour I'll take on 16 ounces of fluid.  I personally think I'm on the lighter end of things and couldn't imagine taking on less fluids especially the other week in Colorado."* (Trans Rockies Run, 20 miles of trail running/day for a week.)

Two very experienced athletes I know, one an Ironman coach for crying out loud, the other an experienced racer with 13-14 IMs on his resume, both Kona veterans (!), ended 140.6 efforts in warm conditions 14 and 17 lbs down...concluding their day as guests of the medical tent.  I put this to noted coach/author Joe Friel who answered:

Yes I certainly agree that what is right got one is not always right for another. But in this area I ask myself how many have died in long endurance events from dehydration. Answer: none. How about from hyperhydration? When we tell a athletes that a 2% loss of BW causes a slowing and tell them to come up with a plan to avoid that you know what happens. Drink lots. No limits. They can't imagine they could deviate from that. Are they stupid? Nope. Last death in a marathon was a doctor.  Given a choice for my client to lose -17lbs or die I'll choose weight loss.

And all of this doesn't even get into the matter of how you come up with a plan. What if race day is cool? Or very hot? What if the wind is blowing hard so I'm on the course an extra 30 min? What if humidity is high? What if it's low? What do I do if having a bad day? What if race start is delayed an hour? How many variables are there that we're asking a mid level retail store manager to come up with? Based on what data?

And this doesn't even get into what this person should drink on their plan. Most are easily sold a bill of goods when it comes to sports drinks. If my favorite athlete uses it then it must be good for me.  My experience has been that the more stuff that is in the drink (sugar, vits, minerals, salt, miracle ingredients) the more likely they are to have a stomach shut down. I believe the safest is water with nutrition (sugar or fat) coming from another source. Hydration is not closely tied to nutrition.

That's enough. I'm sure you catch my drift on this.


Lastly, when we interviewed the athletes at Hawaii bike inspection last year, one of the questions was “Do you plan to drink to thirst or drink to a plan?”  82% said plan of one form or another.  I’ve always agreed that there’s no need to micro manage one’s fluid intake and that many of us can be quite comfortable more than a little dehydrated.   Maybe it comes back to the, no one plan is right for everyone.  Think about what Joe Friel said, use your head, your experience from trying different ways during training and racing, do what works for you, and err on the side of dehydration.

From Asker Jeukendrup

Hydration requirements

September 15, 2017


Hydration requirements

Drink too little and performance may suffer. Drink too much and there are other risks.
In endurance sports (and most other sports), getting your hydration just right is important. Dehydration is common and may cause performance to suffer. Overhydration, although less common, can be a much more serious issue. Knowing how to hydrate properly will help you achieve peak performance and avoid serious risks.

Why do we sweat?
In order to make sure body temperature stays within acceptable limits and we don’t overheat, we sweat. The higher the exercise intensity (read as higher speed/pace/power output), the more heat is produced and the more we need to sweat to stay cool. In hot conditions, it is even more important because sweating may be the only way we can cool down our bodies. Other factors can affect sweat rate. Sun, high humidity, insulating clothing can all result in increased sweat rate. On the other side, shade, wind and low humidity can aid in cooling and reduce sweat rate.

How much sweat loss is OK?
Sweat loss is usually measured as a percent of our body weight. In very short efforts such as a 5K, sweat rate may be high but time spent exercising (sweating) is short so that total body weight loss will likely be low (less than 2% of body weight). As duration increases and more time is spent sweating, losses can easily reach 2-5% of body weight. 
Research shows that performance can begin to degrade as sweat losses go beyond 2-3%. Guidelines from American College of Sports Medicine and International Institute of Race Medicine (Optimal Hydration) respectively suggest targeting 2% and 2-5% body weight loss. CORE aligns with these guidelines.

Why is dehydration a problem?
When we lose too much sweat we become dehydrated; this reduces blood volume, increases heart rate, and makes it harder maintain our body temperature. It also increases our perceived exertion. All of these reduce our ability to compete and may increase the risk of heat exhaustion and heat stroke.

Why is overhydration a problem?
Drinking too much (overhydration) can lead to a dangerous medical condition called hyponatremia (low serum sodium levels). Early symptoms can include swelling, headaches, vomiting. More serious symptoms include disorientation and seizure. In the worst cases, if not treated, hyponatremia can result in coma and death. The risks of hyponatremia increase significantly with overhydration. If you do not lose weight during your race, you are 7 times more likely suffer hyponatremia.

How do I prevent dehydration and overhydration?
In order to prevent dehydration, it is important to start a race hydrated and maintain proper hydration throughout the race.
Before the race, drink ~500ml during the 2 hours before the start; excess water will be eliminated through urine. You can confirm you are well hydrated by checking that your urine color is pale.
During the race (or training), there are two approaches to hydration.
Drinking to thirst is a recommendation that works fine for the slower athlete: if you are thirsty, drink; if you are not thirsty, don’t drink.
Drinking to a plan can work for everyone, especially if you are going a bit faster, if your race is longer and if you understand your sweat rate. Your planned fluid consumption should always be targeted at a rate that ensures you will not gain wait; a good gauge for this is to consume at or below your sweat rate. If you want to find out how to measure your sweat rate, visit the article Sweat rate calculation.

Pro tips
It is wise to use the early parts of a race when the gastrointestinal tract is working well to absorb both carbohydrate and fluid. Later in the race, even though you may be thirsty, your gut may not absorb as much. Don’t drink excessively, and use common sense. The goal should be to lose a little weight (1-2 kg, 2-4lbs or ~2-3% of body weight) at the finish line.
It is important to note that if bloating occurs and fluids seems to accumulate in the stomach there is no point ingesting more fluids. Reducing your run intensity a bit and giving the stomach some time to pass fluid on to the intestine for absorption will relieve bloating.

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