You'll ruin your knees!
Wow... basically, author Tim Noakes is suggesting that the body just says "I got this" when it comes to extended exercise. Drink to thirst? Really? It's that simple? If it tases good, do it? Some things to ponder here.
From iRunFar.com's write-up on the book...
The Role of Hydration and Performance
Hydration and Thermoregulation
Sodium Balance and Performance
Anti-Diuretic Hormone – the Lynch Pin in Hyponatremic Illness and Death
""...the truth that someday, you will go for your last run. But not today—today you got to run." - Matt Crownover (after Western States)
I just finished reading the book. (Well, OK, I skipped a couple of the chapters that were mostly polemic.) I think a lot of the above is reasonably well accepted these days. Oh, and it was very interesting to learn about SIADH from the book. Hyponatremia makes more sense now.
The thing I could never reconcile about faster runners finishing more dehydrated is, doesn't their blood volume drop? Doesn't that necessarily impact performance? And if your blood volume drops, you have less blood to direct to your skin, so you also sweat less and cool less effectively.
Noakes (heh - iPad corrected to "jokes") says no -- actually blood volume does not decrease with moderate dehydration, even though total body water does. I guess this is conceivable; water is being lost from your muscles as you burn glycogen, and the increased extracellular fluid osmolality will draw more fluid from intracellular space. But -- no, that actually doesn't fly, I think. As you get dehydrated, and don't drink, sodium concentration rises. But you are losing sodium via sweat. Therefore, blood volume must be decreasing. If you drink to thirst -- say, to maintain a fixed osmolality -- you are still down net sodium, so you must also be down net blood volume.
Re sweating, Noakes says this is independent of blood flow to the skin. (But conductive and convective cooling would be reduced with less blood flow to the skin.)
It does seem to be a tenable position, though, that the tradeoffs here tend to come down on the side of moderate dehydration, because you are saving weight. Now... I think it's been fairly well established that STARTING a race dehydrated decreases performance. Which suggests there is some optimal level of hydration one would ideally maintain between fully hydrated and, oh, 5% down.
There is one annoying issue the book still did not reconcile. I had the same problem with "The Runner's Body", cowritten by one of Noakes' former students. Most of the book tells you, Gatorade is evil, you don't need any electrolyte supplementation, and only drink to thirst. But the final chapter talks about how to actually optimize performance, and the critical thing here is taking in carbs as fast as you can. Which requires a fairly large intake of fluid, likely more that you would get drinking to thirst. If I recall, Noakes recommended 600ml / hour of. 10% carb solution, more if the concentration is lower. But what marathoner (other than elites) or ultrarunner has the luxury of this kind of supply? We are generally stuck with Gatorade or equivalent (often watered down); to get the carbs he recommends from the Gu2O you find at ultras will probably put you on the hyponatremic side! (I tried to be careful, but finished Western States with a sodium level of 137, up a few pounds.) I suppose the optimal thing might be to drink 600ml of water / hour and consume gels (ideally electrolye-free, if such a thing exists) to get the right concentration.
Feeling the growl again
His argument may hold for a marathon (say 3ish hours of running). But "sodium sparing" only goes so far, as you indicate you WILL deplete net sodium as time goes on. I agree that for marathon-ish distances, most runners do not need to worry about replacing sodium...though I am strongly skeptical that Gatorade is "evil". I find it hard to believe that people will take in so much as to get too much sodium in their system.
For ultras, I simply don't believe that your body can sweat for hours on end while somehow not depleting electrolytes. And I'd challenge him to provide solid data that it can.
MTA: I'd call most of his "dogma" statements straw men, as most of those are statements that are heard but not necessarily widely accepted (certainly by informed sources, at least). The last one...about rehydrating after the event leading to severe over hydration and hyponatremia...well, when I've run as much stuff as I have without seeing a single case of this, again I'd say I am highly skeptical of the evidence behind this statement.
"If you want to be a bad a$s, then do what a bad a$s does. There's your pep talk for today. Go Run." -- Slo_Hand
I am spaniel - Crusher of Treadmills
So on a 70 degree morning I lost 7 pounds in 10 miles of really easy running - I am a heavy sweater. Lets say I can lose 1/2 a pound of hydration per mile
At some point I have crossed the line between moderate dehydration and significant and even life treatening.
If I can process 35 ounces of liquid and hour for 24 hours = 840 ounces or ~ 7 gallons. I do believe if I drink just water - No electrolytes I will be in a life threatening position.
It does make sense that your body tries to keep some equalibrium and since I am a heavy sweater, but also a heavy salt ingester ~ I often get salt lines on my shorts and crusted salt on my face. So there is some merit to taking in a bit less salt and still being OK.
No electrolytes for 20-30-40 hour races does not make a lot of sense
No eletrolytes for a marathon - Makes some sense.
Maybe I sweat at a greater rate, because I take too much salt and my body is trying to flush it by sweating ??
Long dead ... But my stench lingers !
Nah, that is what your kidneys are built for...not your sweat glands.
Noakes cites a lot of evidence that sweat glands adjust too. That looks pretty solid to me.
I did not say they don't participate, but I strongly question the thought that someone sweats MORE for the explicit reason of getting rid of excess salt. If this were the purpose of their function, then what do they do when you are not over-heated enough to sweat? Why would not all of us then sweat more to get rid of more salt? I've run both with and without taking salt tabs, I can't notice any significant difference in sweating or salt on my clothes afterwards.
Sweat glands respond to temperature, not salt content. I am sure the concentration of salt in them changes somewhat depending on the level in your blood but I still contend that the kidneys are your primary excretion mechanism when your sodium gets too high.
Sweat glands are thought to be evolved from dedicated salt glands in other types of animals....whose kidneys do not function as efficiently as in mammals. In mammals, with higher evolved kidneys, we see the divergence in function.
I strongly question the thought that someone sweats MORE for the explicit reason of getting rid of excess salt. If this were the purpose of their function, then what do they do when you are not over-heated enough to sweat? Why would not all of us then sweat more to get rid of more salt? I've run both with and without taking salt tabs, I can't notice any significant difference in sweating or salt on my clothes afterwards.
I don't think the idea is that you sweat more, just saltier. And IIRC the sweat glands are supposed to take a few days to adjust to a saltier diet, so taking salt tabs during a race wouldn't necessarily be expected to produce saltier sweat. If you're interested I'll go back and dig up his references. There's at least a whole chapter on this kind of stuff.
What they do when you are not overheated enough to sweat is nothing; the kidneys take care of acute control of electrolyte balance. It does make sense, to me at least, that saltiness of sweat would be something your body can adjust.
It wouldn't make sense to sweat more to get rid of salt anyway, without better sweat glands, because sweat is always hypotonic. Suppose we didn't sweat any salt. Then we would become hypernatremic faster, increasing the burden on the kidneys.
His argument may hold for a marathon (say 3ish hours of running). But "sodium sparing" only goes so far, as you indicate you WILL deplete net sodium as time goes on. For ultras, I simply don't believe that your body can sweat for hours on end while somehow not depleting electrolytes. And I'd challenge him to provide solid data that it can.
His argument may hold for a marathon (say 3ish hours of running). But "sodium sparing" only goes so far, as you indicate you WILL deplete net sodium as time goes on.
Of course you will deplete electrolytes. The question is, what are the consequences? Noakes' main point is that they are not nearly as dire as the sports-drink manufacturers would have you believe. I agree that a 100 miler is a different beast than a marathon. What happens if you just drink water (and carbs!) to thirst, ideally to maintain blood sodium around 140? How dehydrated do you have to get before bad stuff starts to happen? What is it? It's not hyponatremia. It's probably not cramps. Noakes argues that it's not heat stroke. It's probably cardiovascular stuff with extremely low plasma volume. It is rather frustrating that Noakes doesn't really talk about actual negative consequences of extreme dehydration (other than cases where there is no drinking at all, i.e., extreme hypernatremia). Do you know, Spaniel?
He provides lots and lots of details on actual cases of hyponatremia in endurance sports (many, including at least 12 deaths), as well as on actual cases of heat stroke (few, and almost all at shorter distances).
I'm tempted to do a personal experiment here, and take no salt at my next 100 miler (Cascade Crest, August), drink only water, and find gels with no electrolytes (if such even exist). I'll still get some salt in foods. Normally I get all my carbs from sports drinks (marathon), or sports drinks plus food (ultras); I'm not big on gels. Yes, I'll get very dehydrated (if I'm careful not to overdrink). I'll have to investigate their medical checks to make sure I won't get pulled from the course.
They used to pull you at Western States if you were down more than 5%. Until they noticed that the winners were always those just short of being pulled.
You won't get pulled. Near as I can recall, there are no mandatory medical checks. Certainly not at the halfway point (Hyak, which I worked one year) nor stations after that (which I paced through). Now, if you look bad and ask for medical treatment, you may get a time out...
Dunno if I would use Cascade for the experiment. On the one hand, it is a hardcore race with changing weather and lots of climbing. So it will work you harder than, say, JJ. On the other hand, it is a hardcore race with changing weather and lots of climbing. In the middle of nowhere. If your experiment goes poorly, you might be looking at some Interesting Times getting you out of there.
>> They used to pull you at Western States if you were down more than 5%. Until they noticed that the winners were always those just short of being pulled.
When did they stop doing this? Do you suppose Ann Trason's record would have been bettered sooner if certain gals hadn't been pulled? (I'm asking this not knowing who has really been pulled or given time outs over the years)
I don't remember. I heard this at the medical session I went to the before the race. I think they will still pull you if you are too low, but I don't know what the number is now, if there is a hard number. A friend of mine did get held for a couple hours at M85 for being up 6%. (Fortunately she still finished, in about 29:00. Last year she was top 10. She wasn't having a good day this year anyway, because of the wonky weather.)
Interestingly, I also saw a chart of data from WS that, if I recall correctly, was finishing blood sodium vs. weight gain/loss... with an opposite slope (slightly in the direction of higher sodium = more loss) than all the charts in Waterlogged, as well as in Lore of Running. But I may be misremembering what was charted (as well as what I'm comparing it against in Waterlogged). It was explicitly mentioned that this relationship (whatever it was) was the opposite of what was in Lore of Running. The correlation was not all that high, though.
I guess wouldn't be all that surprising to see data points all over the map on sodium vs. weight loss after a 100, because people are consuming salt pills according to whatever strategy they think is best, as well as water. So you could easily be dehydrated yet hyponatremic if you drank only water, but not quite enough to replace what you lost, or conversely, overhydrated and hypernatremic, if you drank a lot but took more salt than you needed.
GreyBeard
2020
I recently fell apart at SD100 by drinking water (too much probably) and no salt partly b/c I'd heard Noakes on Ben Greenfield podcast say we didn't need it. I think highly of Noakes but didn't realize the basis of his ascertion was limited to marathons and hiking.
FWIW, Noakes would say this would be the worst possible thing you could do (if you drank too much water). Also FWIW much of his personal research in these areas was done at the Comrades "Marathon" (90K).
I still want to know what the downside of depleting sodium in an absolute (not blood level) sense is supposed to be.
bhearn, if there are a couple of the most relevant references I would be interested in reading them, thanks. Don't kill yourself trying to share the whole bibliography.
The consequence of depleting sodium in the absolute sense is that eventually your serum level will drop. IIRC I heard him make some statement about getting sodium out of the bone or something? Well that would be a slow process and not really significant compared to the rate at which one would be sweating it out.
The consequence of extreme dehydration, I agree, would most likely be cardiac-related, at least at first. Racing heard, dramatic drop in performance. But then sweating would shut down as a consequence and you would begin to overheat as well.
I do agree that typical race-related water loss is not going to be the primary cause of most heat stroke, however when it reaches an extreme level and sweat production decreases or ceases then the two could be related. I don't know about you but I have been dehydrated to the point that sweating stops; things get ugly fast from there!
I wasn't arguing the cases of hyponautremia he may have referenced in endurance sports. To me more clear, what I was skeptical of was the dramatic statements about the effects of re-hydrating AFTER exercise to the point of clear urine. Hyponautremia clearly happens, though it does not seem that most who have ended up there were doing reasonable water consumption, the anecdotal reports I've seen typically report excess intake.
I'm still not quite clear what is argument is about taking in electrolytes being bad. Over-hyped, OK, we all know the Gatorade marketing geniuses do that. But it would seem the consequences of too little salt are way worse than too much. If you try your experiment please be careful out there, that's a long and secluded race to get in trouble.