Drink To Thirst .... Sort Of

Triathlon Forum
1

Hello All,

From Training Peaks:

https://wpassets.trainingpeaks.com/wp-content/uploads/2018/05/21131123/18120-should-you-drink-water-to-thirst-blog-700x394.jpg

https://www.trainingpeaks.com/blog/drink-water-thirst-hydration-endurance/?utm_source=tpnu&utm_medium=email&utm_content=nonuser&utm_campaign=20180603_weekly_news_nonuser

Excerpt:

"…YOU’RE TRAINING OR RACING LONGER HOURS/DISTANCES IN TOUGHER CONDITIONS?
However when you’re sweating over many hours (either in a single day, or collectively over many days back-to-back) and accumulating large sweat and sodium losses in a condensed period of time, I remain wholly unconvinced that drinking water to thirst is enough to optimize your hydration and performance. There’s just too much solid evidence out there showing athletes at all levels using electrolyte supplements to very positive effect (and the opposite when they don’t).

If you’re training/racing longer distances, especially in hotter/more humid conditions, it’s definitely worth building a considered hydration strategy. Your plan should be individualized and flexible enough to be tweaked on the go. It should also utilize biofeedback (including a big reliance on your sense of thirst) to determine how much fluid and sodium you take in. Taking this free online Sweat Test can help you get started.

In reality most people’s final hydration plan should involve some strategic and premeditated consumption of fluids and sodium, balanced with a healthy degree of ‘drinking to thirst’ to ensure that you don’t end up vastly over (or under) doing your intake on a given day."

2

Ok- the big problem with the drink to sweat rate method is that your sweat rate has absolutely nothing to do with your fluid ABSORBTION rate! Anyone could easily ingest well over a gallon of water, or sport drink in an hour or less, and if you do you could very well die :frowning: Drinking more than you can absorb is the primary cause of hyponytermia in sporting deaths. Hyponytremia has been the cause of dozens of deaths in sporting events over the past two decades. Dehydration has been associated with ZERO deaths during sporting events, ever!
So, what is the point of testing sweat rate when determining a hydration plan? What you need to do is get an understanding of how much you can absorb. The amount of absorbtion rates between adults has much less variability than body sizes. The bulk of studies on this over the past 70 plus years have sited 18-22 oz per hour, at a realitively sedentary state. The harder you are working, the more you will likely sweat, but the LESS you will be able to absorb. So trying to drink more because you are sweating more is not smart, as it increases risk of hyponytremia. DRINK to thirst- your body is smarter than you are! If you are sweating a lot, work on other ways to cool down, such as proper clothing, and using water EXTERNALLY to cool down, and if you absolutely have to, slowing down, which is much better than dying!
BTW- where have you seen studies that show drinking to thirst and not taking electrolytes will slow you down?
The best data I have seen on this has been published by Dr Tim Noakes, who has collected data from literally thousands of athletes competing at IM South Africa, and Comrades Ultra run, and that data shows exactly the opposite of what you are noting. I am pretty sure that the physiology of humans competing in the Southern Hemisphere is the same as the rest of the world, so I find that data, with such a high number of data points, to be highly credible.

3

Hyponatremia has nothing to do with drinking more than your body can absorb. That will just make you feel all bloated. Hyponatremia occurs (in the endurance sports context) when you drink large quantities of water or sports drink that is lower in sodium content than your natural blood sodium concentration, and it dilutes your blood sodium level. In fact, if your body can’t absorb what you just drank, then hyponatremia is not possible. So, in order to become hyponatremic, you have to drink and absorb a large quantity of water.

4

Hyponatremia has nothing to do with drinking more than your body can absorb. That will just make you feel all bloated. Hyponatremia occurs (in the endurance sports context) when you drink large quantities of water or sports drink that is lower in sodium content than your natural blood sodium concentration, and it dilutes your blood sodium level. In fact, if your body can’t absorb what you just drank, then hyponatremia is not possible. So, in order to become hyponatremic, you have to drink and absorb a large quantity of water.

Not true- look it up. BTW- it is literally impossible to drink of absorb fluids with a sodium level anywhere near your serum sodium levels.
And if you want a real world example, just google for the story a few years back of a Sacramento radio station that conducted a contest to see who could drink the most water in a limited number of minutes, don’t remember exactly how many, I think 10 ish. The “ winner” died, an hour or so later, from HYPONYTREMIA.

5

Here is a direct quote from a medical dictionary-

Euvolemic hyponatremia – total body water increases, but the body’s sodium content stays the same

Please note- TOTAL BODY WATER…

This is one of 3 classification types for hyponytremia, but points out a very important fact that many do not understand.

6

Sorry- last quick but important point- my comment is speaking to the physiological effect of drinking more than you can absorb. From a practical point of view, when you over drink most people will feel very uncomfortable, and stop drinking, or if way too much, probably throw up. And while a few dozen deaths in literally 10s of thousands of participants in sporting events is a very small percentage, it is still a few dozen too many. These types of deaths were almost unheard of pre 1970.

7

If you change the word “absorb” to “excrete” I agree with you. But think about what you’re saying… how would total body water increase from drinking too much water if you do not absorb it. It will just sit in your stomach and do nothing but slosh around and make you feel sick.

8

If you change the word “absorb” to “excrete” I agree with you. But think about what you’re saying… how would total body water increase from drinking too much water if you do not absorb it. It will just sit in your stomach and do nothing but slosh around and make you feel sick.

Yes, It will just sit in your stomach and intestine, sloshing around and making you feel sick, INCREASING your TOTAL BODY water AND triggering transfer of sodium from your blood serum to the water, therefore lowering your sodium serum level, therefore triggering hyponytremia which triggers cellular swelling, including in the brain, which can result in death, fairly quickly. (Not sure I have completely and accurately described all of the details, but I am certain of the general chain of events)
This was demonstrated as noted previously by a Sacramento Radio station and their unlucky now deceased “winner”. I recommend you DO NOT try this at home, as your results probably will not vary:-)

If you don’t want to go through all the muck of the science, just keep it simple, trust your body, test in training, and have fun racing. (It is always my recommendation to error on the side of NOT dying!)

9

Here you go:

Woman dies after being in water-drinking contest
January 14, 2007|From the Associated Press

SACRAMENTO — A 28-year-old woman found dead hours after taking part in a radio station’s water-drinking contest died of water intoxication, the coroner’s office said Saturday.

Assistant Sacramento County Coroner Ed Smith said a preliminary investigation found evidence “consistent with a water intoxication death.” Also known as hyponatremia, water intoxication occurs when the body’s sodium level falls below normal. Overdrinking dilutes the sodium in the bloodstream, causing the brain to swell and push against the skull. Symptoms include nausea, vomiting, weakness and, in severe cases, seizures, coma and death.

Jennifer Strange’s mother found her daughter’s body at her home Friday in the Sacramento suburb of Rancho Cordova after Strange called her supervisor at her job to say she was heading home in terrible pain.

“She said to one of our supervisors that she was on her way home and her head was hurting her real bad,” said Laura Rios, one of Strange’s co-workers at Radiological Associates of Sacramento. “She was crying and that was the last that anyone had heard from her.”

Earlier Friday, Strange took part in a contest at radio station KDND-FM (107.9) in which participants competed to see how much water they could drink without going to the bathroom.

Initially, contestants were handed eight-ounce bottles of water to drink every 15 minutes.

“They were small, little half-pint bottles, so we thought it was going to be easy,” said fellow contestant James Ybarra of Woodland, west of Sacramento. “They told us if you don’t feel like you can do this, don’t put your health at risk.”

Ybarra said he quit after drinking five bottles. “My bladder couldn’t handle it anymore,” he added. After he quit, he said, the remaining contestants, including Strange, were given even bigger bottles to drink.

The winner of the “Hold Your Wee for a Wii” contest was promised a Nintendo Wii video game system. John Geary, vice president and marketing manager for Entercom Sacramento, the station’s owner, said station personnel were stunned when they heard of Strange’s death.

“We are awaiting information that will help explain how this tragic event occurred,” he said.

10

https://www.ncbi.nlm.nih.gov/pmc/articles/PMC2658919/

Here is an article by noates discussing the mechanism of hyponatremia triggered by overdrinking. It seems that it can occur irregardless of how much sodium you are ingesting and is quite unpredictable.

While I don’t disagree with your premise that the safest thing to do is to drink to thirst can you post a link discussing the idea that sodium can cross cell membranes into free water in the stomach and intestines. My rusty physiology seems to recall water being able to freely transit cell membranes this way but sodium and potassium and other things crossing only by cellular membrane pumps.

11

Just my n=1 in cycling - drinking to thirst doesn’t work for me. By the time I’m thirsty, it’s way too late, and I’m in a huge hole that’s impossible to dig out of. I drink to absorption rate whenever I know my excretion rate is going to exceed my absorption rate. For whatever reason, I basically never get thirsty, except about 15 minutes after I finish, or when I reach severe dehydration. That’s why I always read Noakes research with interest, then keep on doing what I do anyway.

But that’s just me - I make no claim that it would work for anyone else.

12

https://www.ncbi.nlm.nih.gov/pmc/articles/PMC2658919/

Here is an article by noates discussing the mechanism of hyponatremia triggered by overdrinking. It seems that it can occur irregardless of how much sodium you are ingesting and is quite unpredictable.

While I don’t disagree with your premise that the safest thing to do is to drink to thirst can you post a link discussing the idea that sodium can cross cell membranes into free water in the stomach and intestines. My rusty physiology seems to recall water being able to freely transit cell membranes this way but sodium and potassium and other things crossing only by cellular membrane pumps.

Unfortunately my haste in reply resulted in a badly stated (wrong) explanation. Here is a correct and proper explanation:
Hyponatremia occurs 1) when the hypothalamic-renal feedback loop is overwhelmed by increased fluid intake, 2) the feedback loop malfunctions such that ADH is always “turned on”; 3) the pores in the kidney are always “open” regardless of there being no signal from ADH to be open; or 4) there is an increased ADH even though there is no normal stimulus (elevated serum sodium) for ADH to be increased.

Bottom line- drinking more than you can absorb (process), will result in excess total body water volume, which can result in hyponytremia as described above.
Noakes has published an abundance of excellent research and studies on this. Sorry for my hack job in trying to explain the science.

14

I’d always like to compare “drinking to thirst” with “cycling by perceived exertion”.

You can get really good at it by trial and error and by experience. Really good.

Unfortunately there are many out there who have no interest, patience or “talent” to listen to their body.

They need crutches such as “power” and “fluid-loss” to at least get them in the vicinity/ballpark of not screwing up badly.

That unfortunately (for them) leads to less than desirable outcomes if external factors change the rigid and prescribed “game plan” (such as weather for power or heat/cold/wind for fluids → possibly hyponatremia).
.

Sure. People should do what works for them rather than religiously follow doctrine.

15

My biofeedback approach relies not just on thirst but on how salty/crusty my sweat is! If it’s dripping in my eyes and causing little to no irritation then I’m generally good. If it’s starting to burn my eyes and tastes salty that’s normally a sign I need to take on more fluids (and/or slow down a bit and let my body absorb the fluids I’ve already taken on). If I’ve got crusty salt deposits building up around my eyes and mouth then things are getting pretty bad and unless I’m within range of the finish line I might need to slow right down or even go sit in the shade for a few minutes.

There’s also no substitute for experience and training at race paces in conditions similar to what you’re likely to experience on race day. Easier said than done if you live in a cool area and have entered a race in a hot one, but unfortunately in my view if you find yourself toeing the start line on a hot and humid day with no recent experience of training hard in those conditions then you need to factor that into your race plan, be more conservative with your approach, and be prepared to back off if needed.

16

The science is hard and it seems even Noates notes :0) it is not well understood. It also seems random who gets affected the worst. I have had heat exhaustion while being well hydrated (as evidenced by peeing relatively dilute urine) at St. Croix 70.3. Also have bonked during an ironman. Likely not hyponatremic as I have trouble taking in large amounts of fluid.

17

Waterlogged is a worthwhile read. Elite runners often loose 5-7% of body weight over the course of a marathon. That’s good enough for me. There’s already enough things I tend to overthink and worry about.

18

Yes, It will just sit in your stomach and intestine, sloshing around and making you feel sick, INCREASING your TOTAL BODY water AND triggering transfer of sodium from your blood serum to the water, therefore lowering your sodium serum level

This is simply not true. Exercise associated hyponatremia is primarily dilutional with a smaller part being due to variations in excretion. There is no transfer of sodium to the gut. Serum sodium is diluted by hypotonic solutions (usually plain water). Were the water in the gut “not absorbed”, this isn’t part of total body water as the term is used in physiology. The gut is technically outside of the body, and the contents don’t factor into our renal/electrolyte equations.

http://cjasn.asnjournals.org/content/2/1/151.full

19

I have a race fueling strategy that I have developed over years of reading and significant trial and error. I know how many calories that I need to race. The variable is how much water on top of those calories.

Personally, when I am on the bike and start to get hungry that is my early signal that I need water. I’ll grab a water bottle at the next aid station, drink as much as I can by the end of the station, and the hunger goes away. Repeat as needed throughout the race.

There is no one size fits all fueling and hydration strategy. Part of becoming a better long course racer is figuring out what works for you.

20

So, what is the point of testing sweat rate when determining a hydration plan? What you need to do is get an understanding of how much you can absorb.//

The point is to find out if you are a heavy sweater/excreter. No one is saying that you can replace all that you lose if you are in the heavy category, you dont have to in many cases. You body has a store of all this stuff, along with calories to burn. But just like the burning of calories and the fact you can not replace all you lose, you just want to do your best to mitigate the losses. On really cold days that are raining, I can get by with a bottle of water and coke. On a really hot day that is dry, I cannot keep up with losses, but I can do enough to last 4 hours with my bodies stores.

You are right, it is silly to drink more than you can absorb, but to neglect to know what you are losing in the first place, well that is a recipe for disaster for a lot of people…ANd yes, there are every type of athletes out there, ones like PNF who can drink a few sips of water and win Kona, and others that have to take 40 salt pills with enough water to absorb them to have their best day…Why wouldn’t you want to know which one you were, or in-between??

21

So, what is the point of testing sweat rate when determining a hydration plan? What you need to do is get an understanding of how much you can absorb.//

The point is to find out if you are a heavy sweater/excreter. No one is saying that you can replace all that you lose if you are in the heavy category, you dont have to in many cases. You body has a store of all this stuff, along with calories to burn. But just like the burning of calories and the fact you can not replace all you lose, you just want to do your best to mitigate the losses. On really cold days that are raining, I can get by with a bottle of water and coke. On a really hot day that is dry, I cannot keep up with losses, but I can do enough to last 4 hours with my bodies stores.

You are right, it is silly to drink more than you can absorb, but to neglect to know what you are losing in the first place, well that is a recipe for disaster for a lot of people…ANd yes, there are every type of athletes out there, ones like PNF who can drink a few sips of water and win Kona, and others that have to take 40 salt pills with enough water to absorb them to have their best day…Why wouldn’t you want to know which one you were, or in-between??

AGREED! Just making a point to get people to think about it, as there are many who foolishly try to drink to sweat rate :slight_smile: Absolutely test through training- I tend to recommend starting toward less, then adding as needed. For me, in terms of water, I range from a bottle over 2.5 ish hours on a cooler recovery effort, to slightly over a bottle (20 oz) an hour on a hot, hard effort day. I weigh in at 150 lbs.