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I am particulary interested in some of your points which I have pasted below:
"Finally there is now good evidence that humans evolved as long distance runners on the African savannah and that our ability to sweat (and become dehydrated) allowed us to outrun faster antelope whose inability to sweat (and to become dehydrated) prevented them from maintaining low body temperatures during very prolonged (4-6 hours) exercise in extreme dry heat (between 40-46 degrees Centigrade; 104-115 degrees Farenheit) when both had limited access to water. The most effective hunters would be those who developed the least thirst despite high levels of dehydration since they would have been the most likely to continue running for so long and therefore most likely to kill their quarry.
This evolutionary model predicts that the best endurance athletes will therefore be those best able to run without becoming thirsty even though they lose large amounts of weight. The low drinking rates of most of the world’s best endurance athletes in marathon, ultramarathon and Ironman triathlon races provides anecdotal support for this surprising hypothesis."
I'd like to bring up an associated point which I kind of joked about in a posting above. You mention that there might be an evolutionary thing here, in that the best might be able to continue running for a long time with low sweat rates despite dehydration. I want to bring in this relationship between dehydration, rapid fluid ingestion and SIADH kicking in. Let me explain further. In many Ironmans, athletes spend 60+ minutes in a long sleeve wetsuit, in warm water temps which arguably should in many cases be wetsuit illegal. They exit the swim dehydrated and soon start pounding back liquids.
Let's take a step back to that human ancestor of ours, outrunning the antelope. Now, I would guess that our evolutionary mechanisms do not take into account the ability to drink while exercising and severely dehydrated. The ancestor of ours had no drinking options on the fly. Only when he stopped and was safe, was he able to take in liquid. Until then, his kidneys were "shut off" to conserve liquid.
Move back to modern day triathlon. You are dehydrated from the swim. The kidneys are trying to conserve liquid...you hit multiple aid stations during the bike, and are still dehydrated...you take in several liters over say the first 90K....but your kidneys are not processing this stuff. SIADH has kicked in. It is cool and you are not sweating either....suddenly you are several lbs overweight.
What are your thoughts?
Anyway, I would really like to see you publish an article with Slowman and any others on this topic. I'd be glad to participate in any way and get it out to the mainstream triathlon publications if it helps save people from near death ordeals and 4 years of gradual recovery.
BTW, it was very cool that Dr. Noakes came on board to defend his position. But how did he know he was getting dissed on Slowtwitch? Dev...?
Empfield (me) PM'd and emailed Noakes w/questions. obviously, he's much better able to answer my questions which, notwithstanding his comprehensive answer, are still open. they relate to in-race self-diagnostics; whether there's a difference between a hydration protocol that is safety-specific versus performance-specific; and the much-ascribed to him ambivalence to in-race salt intake. i hope he will answer, in particular because the Noakes views that i have read are directed to the care giver, medical director, etc., that is, there's not yet a lot of meaty stuff the athletes can hang onto past, "don't drink if you're not thirsty." yes, there are personal-sweat-measuring tools, but i'm not sure to what degree that falls down when i, who live in the high desert, have as my A race an event in kona. there must be more for the end user. therefore, i look forward to the answers and hope they come.
as for man v antelope, for all the respect i have for the doctors who're on the front lines doing the research (noakes and coggan among them), i've got a problem with the pre-history analogies. as regards race protocol, ought i to warm up before i commence? did my ancesters? further, i'm german/scot. did my ancestors adapt to a different way of life, and ought my fluid protocols to likewise alter, or not? you, dev, made mention of the adaptations you suspect your ancestors made to its exceptionally humid clime, and this (you think) caused you to react differently than would, perhaps, i. were i to follow the prehistoric DNA argument, i must assume my mojave desert (where i live) diet should consist of acorn mash, pine nuts, and the fly larvae lining the bottom of mono lake. if my stomach can't withstand native american diets (it can't), and the native american can't be healthy eating as a european does (he can't), is it appropriate to assume digestive systems have changed but all-things-hydration have not? i'm not using this to argue against the Noakes protocols for hydration, i'm just not a huge fan of basing medical advice on how my ancestors survived 1 million years ago.
that established, i'll bet i could catch the antelope. how to start the fire needed to cook it, that's where i'd fall down. i don't think we're done with this discussion yet.
Aha! I tell that to my spin instructor the next time she tells me I should bring a water bottle to class.
BTW - Does this make me higher or lower on the evolutionary ladder? I really don't need to hunt since we have a lot of grocery stores nearby.
At any rate, I only wish my thirst mechanism was even remotely well tuned. When I started keeping track of before and after workout weight I found myself surprised many times by how little or how much I had lost, frequently without any substantial increase in thirst. There were several times during a longer (10-15 miles) run where I would suddenly stop sweating, and of course my body temp soared, I'd make it home at substantially reduced speed and discover that I'd lost 4-5lb...and still not be really thirsty. Other times I'd be really thirsty and drinking much larger amounts of water than normal, still run or bike fast and come home losing only 1-2lb. In other words, there doesn't seem to be a clear correlation for me between thirst and performance, but a definite correlation between dehydration and performance.
I'll have to keep track of this tomorrow, forecast highs in the 90s and the typical Floriduh sauna humidity. I'll see how 80+ miles feels!
You just never know who will show up on Slowtwitch! Thanks for joining the discussion, and sorry to be late back to the game. I lost track of this thread and just learned of your post. Though you say you will not respond to further posts (which is unfortunate, as you have a lot to contribute), I wanted to respond for the sake of the completeness of the thread.
Your point is well taken regarding the EAH in the literature. However, in this instance I was not referring to the literature. Rather, I was referring to a rather crusty internist/nephrologist I encountered during my early training, who first brought your work to my attention. I may be taking some liberties with his exact words, but his response to my questioning was along the lines of, "You know, a lot of us were discussing this before Noakes was publishing so much. Fortunately, Noakes is now making it common knowledge. You should read these papers, they will keep you from killing people." I made the (perhaps erroneous?) assumption that this was something that had been kicked around at nephrology meetings before you began publishing so widely on the subject.
Perhaps "evangelist" is the wrong word. I did not mean to be offensive. Rather, the point I was trying to make is that you tend to argue your points rather voiciferously. For the record, while working the medical tent at a marathon a couple of years ago, I was labeled the "Sodium Nazi" by a couple of ER residents who were hot to stick large bore IV's in everyone who walked (or was carried into) the tent. I think Dev and I discussed that incident at one point...
In any case, I think I made it clear in my comments that I think your work on EAH has been a great public service, and I stand by that. In fact, a few of your papers are required reading for the medical students and residents who attend my lectures on EAH, heat illness and exercise associated collapse. They are also cited in my book, on account of which I still occasionally receive angry e-mail from coaches and athletes who explain to me the need to drink "as much as is tolerable". You can't convince some people...
Dr. Philip Skiba
PhysFarm Training Systems
Coaching and Consulting for World Champions, and You.
You asked so nicely that I could not justify not responding.
Before I begin it might be helpful to add some other biographical data. I began running in 1969 at the time when we were advised to avoid drinking during exercise. I spent much effort in the 1970’s trying to change that advice and even wrote some articles on this topic which were published in two running books in the US. But when we saw the first cases of EAH in South Africa in the early 1980’s, I realised that the pendulum had swung too far and that we had to qualify the advice we were giving.
Over a 21 year period I completed more than 70 marathon and ultra-marathon running races and a host of other standard triathlons and cycling races. I did not ever finish a race feeling thirsty. When I performed less well than I expected, the diagnosis was never very difficult. Since I always drank the same amounts, changes in my drinking behaviours could not have been the cause for either my better or worse performances. Rather the obvious cause was my preparation; when I performed well my preparation had always been ideal. I often wonder if, when we perform poorly, we look for an easy scapegoat. So, for example, we explain our underperformance on the basis that we must have drunk too little water or salt or whatever. How possibly could our preparation have been at fault? This inability to be self-critical provides fertile soil for exploitation by commercial forces.
On the other hand, as described in Lore of Running, I underperformed on a number of occasions when I failed to ingest enough carbohydrate and developed the symptoms of hypoglycaemia (low blood glucose concentration). I concluded that, especially in events lasting more than 2 hours, carbohydrate intake had a much greater impact on my performance than did my rate of fluid ingestion.
This may seem obvious today but before the mid-1980’s we did not believe that ingesting carbohydrate during exercise aided performance – all the emphasis at that time was on fluid ingestion being the crucial determinant of performance. We had to learn from personal experience that carbohydrate ingestion during exercise was perhaps even more important than fluid ingestion. This was confirmed in the laboratory for the first time only in the late 1980’s.
Now in answer to your questions.
1. Is salt intake necessary during prolonged exercise like the Ironman.
The short answer is that no one has yet provided good evidence that salt intake beyond the homeopathic amounts present in sports drinks is necessary to sustain performance during something like the Ironman. This does not mean that the case is conclusively proven; just that there is no definitive support for this practice at present. Interestingly our and other’s data suggests that the body probably has a reserve of sodium stored in an unionized form, perhaps in bone and skin, that can then be activated in the short term should a deficit in the blood sodium content develop. However this is still a controversial issue.
But more to the point is the absolutely clear evidence that subjects who drink to thirst will maintain or increase their serum sodium concentrations whether or not they ingest salt during exercise. Only in those who drink in excess of thirst and who either maintain or increase their weight during exercise is their some evidence that the extent to which the blood sodium concentration falls will be reduced (but not prevented) by the ingestion of sodium during exercise. (This fall can only be prevented by drinking less). Of course this finding has been seized upon by the sports drink industry as absolute evidence that sodium ingestion is essential during exercise. What they have failed to say is that if athletes just drank less during exercise (ie to thirst), they would not need to ingest salt in order to maintain their blood sodium concentrations. This we have known since blood sodium concentrations were first measured in runners in the 1960’s.
We have also shown in two separate studies that salt ingestion does not influence the blood sodium concentration in Ironman triathletes who drink according to thirst. In a series of laboratory studies we also failed to find any real evidence for a major beneficial effect of sodium ingestion during exercise of short to moderate duration (up to 3 hours).
The main benefit of sodium ingestion is that drinks with sodium (and glucose) are usually more palatable than are those without salt in the relatively low concentrations - less than 20mmol per litre - that athletes find palatable during exercise.
In the past month or so, my colleague Dr Tamara Hew has taught me something which may be of critical importance. On the basis of some interesting and preliminary data, she has concluded that the body must regulate its sodium losses during exercise, probably in order to protect the blood sodium concentration. In other words, the amount of salt that is lost in sweat during exercise is not a random phenomenon but must be tightly controlled. It is common knowledge that the amount of salt lost in urine is tightly regulated by different hormones and is one of the key functions of the kidney.
But during exercise, the main site of salt loss is in the sweat, not in the urine. Why would we believe that this loss is not just as tightly regulated as is the loss of sodium in the urine? It does not make sense to think otherwise.
So Tamara’s conclusion is that the amount of sodium lost in the sweat must be controlled just as is the amount of water that is lost, and all are regulated to insure that the homeostatic balance in the body is protected as best as possible. We know that the amount of water that is lost as sweat is regulated in proportion to the elevation in body temperature (or the rate at which heat is being produced); the amount of sodium that is lost must be regulated in order to minimize changes in the osmolality of the blood (at any given sweat rate). In addition, the body seems to have the capacity to remove or add sodium into the blood stream from an unionized (stored) form; this would provide another buffer against sudden changes in blood sodium concentrations (and osmolality) in persons who are sweating profusely during exercise. Depending on the interactions between all these different processes, so athletes will either sweat more or less and drink either more or less during exercise.
The point of all this is perhaps to suggest that the body is designed as a complex system and when one tries to analysis it too simplistically, the conclusions that one draws may be wrong. The clearest point is that we are genetically different and will respond quite differently to the same stresses. Thus some unable to defend their serum sodium concentrations and osmolality will become thirsty at low levels of sweat and water loss whereas others will protect these variables so well that they will not become thirsty until they have lost substantial amounts of body water (since it is the change in the osmolality of the blood that determines thirst).
But given the freedom to choose, the body will tell you when you need water (you will be thirsty) and when you need salt (you will develop a salt-craving). The ruthlessly selective processes of evolution provided us with these essentially fail-safe controls. We just need to learn to listen to and to obey them. And not to assume that general advice will be ideal for everyone.
2. Are my drinking guidelines aimed at safety or performance and would the advice be the same for a Kenyan trying for a sub-2:05 marathon as for an Iowan trying for a sub-5-hour marathon?
To be facetious, the Kenyans do not need any advice. A study we have completed with a group of elite runners in Eldoret, Kenya and which is currently in review, shows that they drink very little during both training and racing. Under all conditions, they drink according to their thirst and it seems that they must have a high thirst threshold since they drink so little (ie they must be able to protect their serum osmolalities very well despite large losses of body water). Their approach fits nicely with the evolutionary hypothesis that the best hunters were likely those with the highest thirst thresholds and who had a lesser need to drink during exercise.
Of course the usual answer from the advocates of the “drink as much as tolerable” school is: “Imagine how much faster the Kenyans would run marathons if only they forced themselves to drink more!” I have spoken to our very best South African (2:07) marathon runners and they are all of the same opinion – it is not possible for them to drink more than about 200-400ml per hour (7-14 oz per hour) when running at 3 minutes a kilometer; nor do they feel the urge to drink more; nor do they see that drinking more would be of any advantage. One such runner told me that as he loses weight during the marathon, he feels lighter and faster.
I would guess that a 5 hour marathoner sweats at a rate of about 300-400ml per hour (about 10-14 oz per hour) and would not likely drink less than that since he or she run so slowly, each has so much time to drink. In addition these slow runners have usually been advised that the fatigue they feel can be prevented by drinking more. Rather, in my opinion, they would probably benefit by being told that they need to be careful how much they drink during exercise.
In summary, then, the advice to the best and the slowest is exactly the same. Drink to thirst and you will optimize your performance. This conclusion that drinking according to the dictates of thirst optimizes performance is also supported by all the published literature (see my recent article in Journal of Sports Sciences and my debate with Dr Mike Sawka to be published in Medicine and Science in Sports and Exercise in the next few months).
3. Mid-race diagnostics for the detection of hyponatremia.
Again, if you follow the advice of drinking only according to the dictates of thirst you cannot become hyponatremic unless your concept of thirst has been modified by all the information given to athletes so that you actually drink in excess of thirst.
So if you are drinking according to your real thirst and you feel lousy mid-way through a race, it will not be because you are hyponatremic. Nor, incidentally, will it be because you are “dehydrated”. Something else will be wrong (perhaps you did not prepare properly; or you went too fast in the first half of the race; or you are ill).
If you have been drinking in excess of thirst and you think you are hyponatremic, there will usually be corollary evidence to support your diagnosis.
First you will probably admit that you have been drinking in excess of thirst.
Second, you will probably feel bloated and may even hear the sloshing of fluid in your intestines. This may also cause you to feel nauseous. You may vomit clear fluid. The latter is a very strong indicator that the rate at which you are drinking exceeds the capacity of your intestines to absorb that fluid. This will usually mean that you have been drinking well in excess of 1000ml (36oz) per hour.
Third you may notice that your watch strap or ring or race bracelet has become tighter.
Fourth, you will notice that your level of consciousness is altered and that you have difficulty concentrating.
If any of these develop, stop drinking until these symptoms and signs disappear (which will likely take some hours since your fluid overload at this stage would likely be at least 2000ml (72oz)).
B. If you are hyponatremic and you stop drinking the condition will reverse itself.
The problem is that once the brain starts to swell significantly as a result of this accumulated fluid overload in someone who continues to ingest fluid at a high rate (or who receives intravenous fluids as treatment for an erroneously diagnosed “dehydration”), brain symptoms may advance rapidly so that the athlete may go from being mildly confused to developing seizures and becoming unconscious quite suddenly (within minutes) with the risk that the athlete may stop breathing.
We advocate the use of slow (at rates of approximately 100ml per hour) intravenous infusions of high salt (3-5% sodium) concentrations once brain symptoms are present. Such infusions can produce miraculous recoveries in some confused hyponatremic athletes whose confusion can be reversed, as if by miracle, within 5-10 minutes.
To summarize: The rules of drinking that we advocate are the following:
Drink if you are thirsty.
Do not drink if you are not thirsty,
Avoid all out racing efforts when the environmental conditions are severe, especially when it is both hot and humid. If you must race in such conditions, then you need to modify your behavior by going slower. This reduces your rate of energy expenditure and reduces the likelihood that you will overheat during exercise.
Finally understand that the most accurate measure of the efficacy of your drinking regime (other than your thirst) is provided by measuring changes in your blood osmolality (not in your body weight).
These are the guidelines that we advocate in most running and triathlon races in South Africa. Last Sunday approximately 9000 (I cannot find the exact number) athletes ran in the 56 mile Comrades Marathon in times ranging from 5hrs20 minutes to 12 hours in temperatures rising to about 26 degrees C. There was not one case of exercise-associated hyponatremia treated in the medical tent at the end of the race (even though there were 45 drinking tables on the course). A total of 150 athletes were treated in the medical tent, none was seriously ill and another 27 were treated in local hospitals with 8 still in hospital 12 hours later (diagnoses not known to me at this time). There were two deaths, neither related to abnormalities in fluid balance during exercise. I am not sure that this proves anything other than to show that it is possible to have athletes exercise for up to 12 hours without there being an epidemic of cases of exercise-associated hyponatremia (or the converse) simply by teaching them to "drink to thirst".
- - So perhaps geared more to treatment rather than prevention?
"don't drink if you're not thirsty."
- - Which never worked for me. By the time I feel thirsty, it's too late to catch up.
"when i, who live in the high desert, have as my A race an event in kona. there must be more for the end user. therefore, i look forward to the answers and hope they come."
- - Opposite of the problem I had in Tucson which was caused by a tendency to sweat enough to keep my skin damp and in the desert dryness, I dessicated in record time. There is an acclimation that takes place to one's surroundings and an adaptation time or procedure that should be followed when going from one extreme to the other. I wish I had some clue as to what it is.
"you, dev, made mention of the adaptations you suspect your ancestors made to its exceptionally humid clime, and this (you think) caused you to react differently than would, perhaps, i. were i to follow the prehistoric DNA argument, i must assume my mojave desert (where i live) diet should consist of acorn mash, pine nuts, and the fly larvae lining the bottom of mono lake. if my stomach can't withstand native american diets (it can't), and the native american can't be healthy eating as a european does (he can't), is it appropriate to assume digestive systems have changed but all-things-hydration have not? i'm not using this to argue against the Noakes protocols for hydration, i'm just not a huge fan of basing medical advice on how my ancestors survived 1 million years ago."
- - 1 million years ago, of course not, but in Dev's case we're only talking two generations or so. Whatever genetic tendencies exist, I would expect them to become less operable as generations pass, and even less operable as an individual acclimates to new surroundings.
One can acclimate (somewhat) to hot or cold climates simply by living in them year round - my eighth winter in Chicago was much easier to bear than my first. And yet after only a year back in CA, I was totally de-acclimated, indicating that perhaps I was back to something that was more natural for me (because I was raised in CA or because my people came from a climate less harsh that Chicago). And perhaps my adaptation to Chicago's winters was eased because my "people" come from colder climates (than CA) in the UK, or because recent generations came from eastern Ohio and Western PA.
Not claiming I have the answers, or even th questions, just sharing some thoughts.
Cousin Elwood - Team Over-the-hill Racing
Brought to you by the good folks at Metamucil and Geritol...
thank you for your detailed and thoughtful response. i have been an ardent competitive runner for about 40 years, and what you write parallels my personal experience. of course that means nothing to most people, nor should it, but my instincts and sense of appropriateness have served me well in the main.
there is one area on which you touched, and on which you spent the most time in your response to me, that i believe may prove to surprise you (when all the ballots are counted). you're leaving the door open on the issue of sodium ingestion, i note. but you also seem to lean toward the view that salt intake is either not needed, or at least is not needed in amounts that exceed those found in your typical sports drink, and that salt, like water, is best ingested only when your body senses the need and apprises you of it through an urge.
you rightly point out that carbohydrate ingestion is much more key, and as i recall this is the one point of intersection between you and your contemporary, dr. coggan. perhaps my memory fails me, but i seem to remember that both you (on the one hand) and andy (perhaps along with ed coyle) both publish on this topic.
as regards sodium, what we see in sport is that the very best athletes swallow salt pills like they're gummy bears, up to and beyond 500mg/hr. this is in addition to whatever salt they might take in through other means (fluid replacement drink, gels, whatever). this raises a series of questions:
1. in a vastly different time and place long forgotten, i seem to remember the issue of osmolality broached not simply with respect to blood serum, but with respect to the ingested beverage. my pentagenarian memory may be conjuring up a parallel universe where biochemistry follows different rules, but i seem to remember the wish to avoid an over-high beverage osmolality, the cause of which was a too-high salt content. these hypertonic solutions presaged, as i remember, diminished gastric uptake. perhaps what i write reflects old science, and in fact hypertonicity does not represent an aborption issue. but for lack of a better term (i'm going to make up my own), let's call it "gastric osmolality," representative of a hypertonic "soup" sitting in your stomach. my question is whether this is an issue or not. if so, then i wonder how these guys can pop all these salt pills and still have gastric systems that absorb. if hypertonicity is not a problem, then i have my answer as to how you can pop salt pills like candy.
2. you write about the body's intent to protect its serum osmolality and, to that end, to resort to salt in its unionized form. you also note the body's ability to protect its serum osmolality. does a stable serum osmolality translate to a requisite number and variety of cations volunteering for their neuromuscular duties? in other words, is serum osmolality protection proof of, or in lieu of, the presence of electrolytes at the neuromuscular level?
i ask this because i can't get past the fact that a fair number of the top ironman athletes resort to the use of salt tablets. one would think that this sort of habit would have an effect. if you took one tab of LSD per racing hour during an ironman, something is going to happen to you. you might DNF, or you might win. but your body is going to have an opinion. likewise, this just seems to me to be too much salt intake for your body to ignore. i would think the body would express itself on the issue of 500mg per racing hour.
Anyway, I seem to have a problem where I am cramping up in races. I am diabetic and quite often when I cramp up I am also high in blood sugar (from adrenaline, racing affects my blood sugar quite differently to training it seems). Being high in blood sugar makes me thirsty and makes you feel quite dehydrated. Usually the day before a race I find myself wanting to piss lots for some reason (and I do..), even though my blood sugar levels are normal and my fluid intake has not really changed. Same on the morning of a race...nerves or something?
Since there has been some great discussion on here, does anyone have any suggestions as to how to prevent these cramps? It has affected me (once real bad, entire lower body cramp) in my last 3 big races (one ironman race, one 2/3 half ironman (ie nz im 2006), and an olympic distance race). All of these races I have had quite high blood sugar whilst cramping it seems and I have also found myself wanting to piss lots the day before despite blood sugar levels being normal and fluid intake staying the same.
I used to get cramp at night when I was younger and would get cramp in my foot quite often when I was a swimmer.
ps am reeally working on the racing blood sugar thing.
The salt thing is really interesting. So many people SWEAR by it. I can't even use endurance formula gatorade if it's not hot out or I retain water for 24 hours post training. It's amazing how differently people regulate sodium. I'd love to read more about it if you have some references!
yes, great discussion, but i would like to mention something about the world wrestling federation element to this thread. yes, andy coggan can be a world class SOB. he's also a world class scientist, and he is the consensus expert in one important element of cycling (training and racing with power).
he is also, as i recall, fairly heavily invested in research on gastric uptake. perhaps it's more along the lines of carbohydrate uptake during exercise, but that seems to me a pretty close cousin to the study of electrolyte balance, serum osmolality, hypervolemia and hyponatremia. carbohydrate uptake has nothing to do with hyponatremia, but both these scientists look at what happens to the stuff you put in your gut during endurance exercise, and how that affects your health and your performance. as such, coggan (who, along with noakes, holds a PhD) is every bit the qualified peer to comment on noakes' work and his views.
furthermore, philbert may not be entirely right in referring to noakes' message as evangelical, there is an element of that in play. one cannot blame dr. noakes for wanting to express his views on an impactful issue of broad relevance, and he's got a rare talent (among researchers) for translating them into a usable protocol at endurance events. lord knows, i'm guilty as charged if one has a problem with converting conclusions based on evidence to systems employed at the user level.
i completely understand if dr. noakes wants to take issue with the tone, or the terminology, expressed in this thread by andy coggan, philbert, or by me. but it would be wrong to say that andy stands alone in his disagreements with noakes (he doesn't) and it would equally wrong to think that andy does not have the bona fides to express his reservations. once we get past the question of how these reservations are written -- the expression of civility or the lack thereof -- we are left with whether you ought to drink more or less during exercise, and what ought to be in that water bottle of yours. i think that's what you want to find out, i know that's the case with me.
1. I find it hard to believe that race performance can be optimized in one who has lost up to 10% body weight.
2. My guess is that we are desensitized to the feeling of thirst. In our society where we drink way more water than we need and pee clear a few times a day, I'm just not sure my body really knows what "thirsty" feels like.
3. The feeling of nausea and decreased gastric emptying that may occur late in a race even when dehydrated might override the feeling of thirst/desire for fluids.
Coach at KonaCoach Multisport
Now I assume that the same probably applies to most professionals. Would an actuary for example like to read on the internet that his professional opinion should be considered suspect because he is only involved in that profession for reasons (including egoism and a lack of altruism etc) that must impact on his ability to function effectively in that profession? My point perhaps is that if the exercise sciences wants to be recognised as a real profession, then its practitioners should act with the ethical decorum appropriate for membership of a valued profession.
I am extremely comfortable to have my ideas challenged. But please present the contrary data so that we can talk about it in an unemotive, mature way. Don't publish claims that are simply wrong and would never stand up in a court of law. The one that really irritates me is to the effect that I ignore the data that disagrees with my ideas. In fact all my contrarian ideas come from a very deep investigation and understanding of the literature which then reveals information that is incompatible with the prevailing dogmas. Rather than continuing to teach and procreate those dogmas (the greatest sin of the teacher or scientist), I then present the evidence that leads me to conclude that the dogma is wrong and then embark on a research program to see whether or not the dogma can be falsified. Much of the evidence for this approach can be found in Lore of Running. Of course those who believe in dogmas may be scared of attempts to falsify them and can find this approach threatening. If an entire industry is based on one such dogma, then a case of mass anxiety and population-wide hysteria can develop.
In The Lucifer Effect, author Philip Zimbardo, the lead researcher of the infamous Stanford Prison Experiment of 1971 (http://www.prisonexperiment.org) details the danger of casting someone as "other" and hence not deserving of our human respect. Without mutual respect, science (like other activities) loses its potential to improve the human condition.
i understand completely what you say. the push-pull here is that i publish a forum board, and the nature of this sort of environment is that my finger must be light on the "delete" button, or else those on this medium feel their views are censored. accordingly, i tend to allow a style of debate in which i might not engage. were i editing journal of applied physiology, that would be one thing. alas, they have not offered me that job.
conversely, if it's triathlon performance you're interested in knowing about, you might not have half a dozen current and former world champions piping up on JAP, as you do here. you just have to be ready to live in the wild west on this and most other internet forum boards.
we have quite a few very distinguished folks posting here, you among them, and i'm very glad you've added your voice. speaking selfishingly now, i'm quite eager to hear anything you might want to say about my questions re salt intake, and whether the body protecting its serum osmolality might be at the expense of performance in a long, hot race.
i might add that i've also heard from a medical doctor -- also phd, and practicing triathlete, whose career has been as clinical director for a variety of big pharma -- that he feels that the presence of salt on one's clothes may indicate the need for a lot of salt during a long hot race, and is probably indicative of a high salt diet. i wonder if these folks are in more peril of hyponatremia of their beverage/food intake is decidedly hypotonic.
With regard to the question of the drink osmolality and the effects on gastric emptying, this is clearly an issue. However if the tablets escape digestion until they are out of the stomach, then this is not an issue. Adding a single 500mg sodium chloride to a drink will, according to my calculations, increase the osmolality of the stomach by 15.5 mosmoles per litre (equivalent to 30mosmoles per litre if you are drinking 500ml per hour). This does not seem to be a great issue since adding 60 grams of glucose (the amount of carbohydrate that we suggest Ironman triathletes should ingest each hour) will increase the osmolality of the drink by 330 mosmoles/litre. This is a hypertonic solution. Ingesting a longer chain carbohydrate will reduce this osmolality effect for as long as the carbohydrate remains undigested which is probably not too long in the human stomach and intestine. Perhaps the point is that, according to these calculations and assuming they are correct, the effect of ingested carbohydrate on the osmolality of the fluid in the stomach is probably much greater than the effects of the relatively small amounts of sodium that are ingested. I suspect that athletes adapt to what they drink and that their gastric emptying might improve with the practice of ingesting fluids and eating foods that cause their stomach osmolalities to be rather higher than we might expect.
With regard to the issue of osmolality protection, you need to remember that the principal design feature of the human body is not to produce feats of great athletic endeavour (although it turned out that being able to run in the heat became an important determinant of how we evolved). In other words we are not designed simply to travel between two geographical points on the island of Kona (and elsewhere) as fast as possible. Rather the priniciple focus of our design is to protect our brains from damage - that is my interpretation. So the brain protects the body osmolality because, if it does not, then the brain cells will die either because they become dessicated by too high an osmolality or waterlogged by too low an osmolality. During exercise the brain does this by altering our behaviors in order to protect itself. So if the osmolality changes in a way the brain does not like, it will signal that you should drink more, or perhaps ingest more salt or perhaps you should slow down or even stop exercising. The effects of changes in osmolality on the muscles and the neuromuscular system (other than the brain) probably only occur when the osmolality has gone well out of the range that the brain will allow under normal conditions when fluids and electrolytes are appropriately available. The times that the brain has trouble regulating the osmolality is when we are stranded in the desert without any fluids or when we drink more than we should because we have been programmed to over-ride the normal brain controls of drinking according to thirst or when we have kidney failure (amongst a few other causes).
Finally there is now good evidence that, at least in short duration exercise, the ingestion of carbohydrate does not act by altering metabolism in any significant way. Rather it probably acts by indicating to the brain that the body is going to be fed during the exercise so that a higher exercise intensity is allowable (by the brain). The sensory receptors for this effect probably lie in the mouth or throat. Perhaps salt ingestion might act in the same way.
What you believe determines what you believe. If you believe that ingesting these rather small amounts of salt improve your performance, then it is probable that they will. But the more probable mechanism is in the brain rather than in the muscles. (Please note that this is a personal hypothesis - it is not a PROVEN FACT).
But be warned that the over-ingestion of salt can be dangerous. A competitor in a recent Race Across America presented to the medical staff after he completed a few days of the race. He had fluid on his lungs (pulmonary edema) and had to stop exercising. He had heard that salt ingestion was good for performance. So he had taken 23 grams of salt each day together with a generous fluid intake. This had expanded his body water content to the point where the membranes of his lungs began to leak fluid leading to his pulmonary edema. Interestingly his tissue osmolality was not affected (since he had retained the sodium) so his brain did not swell as it would have if he had only ingested too much fluid and developed hyponatremia which would have stopped him by causing him to become confused and eventually lapsing into unconsciousness.