Dear JJ,

I agree with you completely. Our study reported in the Proceedings of the National Academy of Sciences showed that 60% of athletes who gained weight during ultradistance events did not develop EAH. Thus to develop EAH it seemed that there were three important factors: overdrinking; SIADH and inability to osmotically-activate intracellular Na or conversely osmotic inactivation of Na+ in the ECF.

The sodium reservoir is thought to be in skin, bone and cartilage.

Potassium losses from the body are very small in both urine and sweat. Potassium deficiency certainly does not occur in healthy athletes under whatever conditions you might impose. This was shown by David Costill in the 1970's. Patients who develop potassium deficiency are those with high blood pressure or heart failure who use specific drugs, one effect of which is to increase potassium losses in the urine. We don't need to invoke "dehydration" to explain this effect.

I am not aware of clear evidence showing that "dehydration" affects blood flow to the gut and so effects fluid absorption. I suspect that there are quite large differences in rates of intestinal fluid absorption amongst individuals. I am aware of some individuals who develop intestinal bloating when they ingest fluid at rates as low as 400ml per hour during prolonged exercise suggesting that that is their peak rate of fluid absorption. Those who develop bloating during prolonged exercise are those who ingest fluid at rates greater than their individual rates of intestinal fluid absorption.

There is no need to evoke "dehydration" to explain this effect.

The evidence is that muscle cramping is due to abnormalities in the neural control of the muscle not to individual electrolyte deficiencies. There is so much calcium in blood compared to the amount inside the cells that it is impossible to develop a calcium deficiency that would effect muscle performance. Calcium is the ion that ultimately causes the muscle contraction in muscle cramping. Thus by logical conclusion, cramping is a sign of the action of calcium, not of its absence.

Potassium deficiency does not occur in human athletes unless they are being treated for high blood pressure or heart failure (or perhaps other obscure conditions).

It clearly does when the dehydration is the result of consumption of a low carbohydrate for a few days.

What is the evidence that performance during prolonged exercise is related to the cardiac output and blood flow to the muscles? Surely if the exercise is submaximal and occurs at submaximal cardiac output and submaximal blood flow to the muscles, there is no reason to believe that it is limited by (submaximal) rates of oxygen delivery?

So although I would like to accept your explanation i am not certain it is likely to be correct.

He gets that a lot....

Again!!!! By my count, that's twice in two years. What is this world coming to?

I must admit, I did a double take as well.

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Steve

http://www.PeaksCoachingGroup.com

Here we go, HOLD ON!!!

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The Triathlon Squad

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Correct. The site from which the fluid is lost depends on the amount of sodium and potassium that are lost with the water. The more sodium that is lost, the more of the fluid loss will come from the ECF.

Sporting performance is strongly belief centred. If you believe that becoming "dehydrated" will effect your performance, then it will. Similarly if you believe that drinking ahead of thirst will improve your performance it probably will. But there is a point at which fluid retention will lead to an impaired performance perhaps as a result as much of brain swelling as of changes in the muscles caused by an increase in their water content.

The interesting point is that it seems to depend where you come from as to your view of how much you should be drinking during exercise. If you are an elite distance runner from Africa you will very likely drink to thirst during training and competition. If you come from Europe or North America, it seems to me that you would be more likely to believe that you must drink to "stay ahead of thirst". Is this because of differences in biology? Or of pre-programming?

Tim,
I appreciate your spending time to defend your research on this board. I read a lot of these articles on sodium supplementation and it has more meaning when somebody that has actually done the research will go toe to toe with critics of the research in an open forum like this. One of the things I've taken from this discussion is the possibility that in some cases it could be the component ingredients of a given product that produces the net positive effect that some athletes experience instead of the sodium. As each product has it's own distinct formulation, the observance by some athletes that certain products work better for them than others demonstrates that supplementation can be useful, but knowing what component is actually producing the positive effect would be far more useful and gets us back to the common adage on this board that we are each an experiment of N=1. The most effective strategy I see from a racing perspective is to use the available research to systematically and experimentally determine our own individual needs and not treat any particular study as gospel.

JJ

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Every night that I run, the thought crosses my mind that there's no way in hell I'll still be running a month from now.

Your question is relevant. Why for example are humans of a particular height and weight (and subject to large geographical differences)? Why are all humans not 3m tall and weighing 200kg? Because evolutionary pressures chose that as humans of 40-120kg would be the most likely to survive. In a 70kg human the carbohydrate reserves are enough to sustain high intensity running for about 2-3 hours after which carbohydrate needs to be ingested. If we had been 140kg we would have had larger stores and could have exercised for longer (although at that weight we would not have been great distance runners).

There is no evidence that humans can run themselves into a catastrophic failure. Even the winners of the Ironman Triathlon do not die at the finish. They walk over to the medical tent etc showing that they finish with reserve. When death does occur it is almost always due to a pathological condition.

Hmmm...as I read that whole entry, why did the words "Straw Man" keep popping into my head?

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http://bikeblather.blogspot.com/

Dear Slowman,

One of the best predictors of risk of developing atrial fibrillation is years of athletic training. Magnesium supplementation has some specific cardio-protective effects. You would be better off trying that as a supplement for your heart condition. Also reduce caffeine intake. But in the end it is continued endurance training that is perhaps the major deterninant of whether or not the condition will or will not settle. So it is a tough decision.

Answers to your questions:

1. Fifteen minutes stretching each day. Stretch during the event.
2. None.
3. In my opinion yes. Fads come and go. Let us see if this one is still around in 5-10 years time. Has there been a dramatic improvement in performance since triathletes began to ingest salt tablets? Also how much are they actually ingesting - grams, tens of grams or hundreds of grams? And how do the amounts they are ingesting relate to how much they are losing and how much is present in their bodies?

BUT: What if the ingestion of sodium acts like that of carbohydrate by acting through the brain to improve performance (and not by altering whole body sodium balance)? We need the group in Birmingham who showed this effect for carbohydrate perhaps to study salt ingestion in the same way.

So I have not been absolutely dogmatic. But my bias is to believe that salt intake will not pass the test of time.

Fluid absorbtion from the gut is passive and solely dependent upon blood flow to where the fluid is, as far as I know. When a person becomes dehydrated the body selectively routes blood away from organs that are not critical to those that are. Not critical organs would include the kidneys, gut, and skin. To say you are not aware of any "clear evidence" that dehydration affects blood flow to the gut and so effects fluid absorbtions suggest you need to go back and reread a basic physiology text or talk to Chris Lieto.

Potassium deficiency is not a "dehydration" phenomenon. Under normal circumstances daily potassium losses are small. But, sweating will increase that daily loss and many athletes are on potassium depleting drugs and many athletes have particularly poor diets from a balance diet perspective or have had recent diarrheal episodes within a few days of any race. To say that an athlete could not suffer from chronic potassium depletion is ignoring real life possibilites. It is easy to diagnose sodium depletion. It is difficult to diagnose potassium depletion. If you want your nerves and muscles to work properly you need the proper balance of both sodium and potassium across the cell membrane.

I would be surprised if the skin were the sodium reservoir in an athlete as the increased skin flow during activity would cause the sodium to equilibrate quickly. I guess cartilage and bone could act that way but they don't seem to have enough mass (edit: cartilage) to be much of a reservoir (edit: or have too much blood flow to be a delayed reservoir, bone). To my mind, the gut is a better candidate as the sodium concentration should be in pretty good equilibrium with the ECF so it would be a large reservoir and it seems to me the diffusion back into the blood would be slow. Regardless of the mechanism, this is pretty much a non-issue to the athlete.

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Frank,
An original Ironman and the Inventor of PowerCranks

I doubt that the families of Cynthia Lucero, Hillary Bellamy, Kelley Barrett and the other 9 or so US citizens (and probably many other unrecorded individuals) who died needlessly from EAH think that this is a Straw Man.

Your concern is valid. However, you seem to be ignoring the many others who have died from inadequate fluid intake and dehydration during exercise from either kidney failure or heat stroke.

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Frank,
An original Ironman and the Inventor of PowerCranks

Wow...now I'm nearly speechless...

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http://bikeblather.blogspot.com/

Fortunately there is not one case in the literature of heat stroke or kidney failure in an endurance athlete that can be linked directly to 'dehydration'.

The point as you know is that because two events occurs simultaneously, this does not mean that they are causally related.

In those studies that have been properly conducted there is no evidence that dehydration effects the body temperature response during exercise to an extent that would suggest that further dehydration would cause heat stroke. Again the key is that the brain is there to insure that the exercise intensity is reduced if the body temperature rises too high.

The most interesting recent work is by Dr Chris Byrne from the UK and reported in Medicine and Science in Sports and Exercise. His work shows that the body temperature response to exercise is determined by the exercise intensity (metabolic rate) not by the level of dehydration that develops during exercise.

My guess is that both conditions are related to abnormalities in skeletal muscle function and that is where we should seek the real causes of exercise-associated heat stroke and kidney failure.

Wow, I have never heard someone so manipulate the interpretation of data to support their theory.

Perhaps you could elucidate for those of us who have been so misguided to think that dehydration might possibly result in eventual hyperthermia as to what the literature shows the cause of these many instances to be? One of the elite females at Sea Otter came across the finish line and collapsed. Medical personnel were seen "packing" her in ice before putting her in the ambulance. I understand she took 3 liters of fluid in the tent and is fine now. To what would you attribute this incident to, if not dehydration?

I participated in an experiment once, running on the treadmill for an hour with it being 90 degrees and 90% humidity because a colleague collapsed 100 yds from the finish line of a 10k with a temp of 107. I got through it fine I suspect because it wasn't enough to dehydrate me. How long do you suspect I could have gone and continued to maintain a normal temperature. According to you, forever. It seems to me that for one to know if dehydration is or is not associated with increased temperature one needs to run these experiments to the point where the subject stops sweating and see what happens to the temperature. Love to see someone getting that experiment through the human uses committee.

While conditons such as malignant hyperthermia most assuredly accounts for some of these instances, it cannot account for all of them. It seems you cannot accept that there are legitimate reasons people are concerned about your recommendations. Life threatening heat stroke seems like a lot more common occurance in athletes than life threatening EAH.

The fact that two events occur simultaneously is not evidence they are not related. Unless I am shown convincing evidence that dehydration and hyperthermia in the athlete are never related I will trust my knowledge of basic physiology and answer that question, true, true, related. I am just blown away.

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Frank,
An original Ironman and the Inventor of PowerCranks

Has there been a dramatic improvement in performance since triathletes began to ingest salt tablets?

Dr Noakes,

That would be a key question to ask.

It's funny, go back 10 years or so and this was not that big an issue in triathlon. Drink some Gatorade, eat a few bananas along the way and thousands of people every year were finishing 1/2 and full IM triathlons. Now the entire triathlon population has, for lack of better wording become salt obsessed. Of course the sports drink and sport nutritional companies have all jumped on board with this and now it's hard to find a sport drink, sport bar or gel that does not have salt in it, and almost every coach is admonishing triathletes to pop salt pills like candy! All of this happened in the last 5 years. What happened? How could we go from one extreme to the other in such a short period of time?

To answer your question, my feeling at a high level is that, "no" their has not been a dramatic improvement in performance with the massive across the board ingestion of salt by the triathlon masses. In fact, when you look at average finish times and most big triathlons, of all distances, the average finish times are getting slower!

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Steve Fleck @stevefleck | Blog

Oh, the irony...


I don't know Frank... That woman was exercising pretty hard for hours, could it be that her core temp was up and she was exausted? Going out on a limb here...

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In fact, when you look at average finish times and most big triathlons, of all distances, the average finish times are getting slower!

Why does that matter? Averages will go down because you have more slow, crappy athletes (like me for instance)
involved.

-Jot

Hey Tim, Thanks for taking so much time for this discussion as its a big issue for all of us.
With your reply here I think you are closest to answering Dan's original question which to paraphrase was "why do I cramp and how can I prevent it?"
In examining further the idea that "abnormalities in the neural control of the muscle" are the cause of cramping, is it plausible that due to sodium lost through sweat and due to sodium moved into the blood that cramping is at least partially caused by normal cell chemisty being altered due to the change in ratios of the ions normally available?
Cheers, Scott Molina