Hello shacking and All,

It appears that what is needed is a more accurate method of diagnosing hyponatremia which is a condition that occurs when the level of sodium in the blood is too low.

While using athlete weight changes before and after racing may be useful .... a rapid and more direct method of assessing the condition at the IV tent appears to be warranted.

Devices like the Pixcell that use only one drop of blood (useful for preemies too) might be a useful tool.



http://www.pixcell-medical.com/

"PixCell Medical Technologies develops, produces, and markets portable medical diagnostic products for point of care testing. PixCell's products are based on its innovative Viscoleastic Focusing (VEF) technology and single use cartridges that enable rapid, accurate and simple blood sampling and analysis. Results are displayed within minutes in an easily readable format. PixCell's mission is to make tests currently restricted to the laboratory more accessible, easy to use and affordable."
"HemoScreen™ is a portable, easy to use, and maintenance free Complete Blood Count device , that provides rapid, accurate and easily readable results."

The condition appears to be very common with more than 3 million US cases per year according to the Mayo Clinic.

http://www.nlm.nih.gov/...y/article/000394.htm


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Cheers, Neal

+1 mph Faster

Hello xtrpickels and All,


I agree with you that the other factors of the experiment should be considered .... in particular the core temperature history of the participant immediately prior to death.




Why am I thinking about extra pickle juice as a cure for cramping, dehydration, and heatstroke? ............. just kidding ............

It looks like humans participating in experiments to expand the envelope of human endurance in hot conditions should have internal core monitoring devices installed or provide other non invasive methods of monitoring biological functions near collapse to predict a timely intervention for preventing death.

Research like that below is pointing the way to non invasive devices that will provide early warning to help prevent incapacitation and death in hot conditions.

http://cs.brown.edu/...ratureEstimation.pdf



"Although the current construction of the KF will not correctly model extreme core temperatures above 39.5°C we suggest that with a few refinements this model could
offer a promising new means of real - time thermal injury risk assessment. We suggest that the other parameters of human health state monitoring are ripe for the intelligent application of machine learning techniques. For the military, performance athletes, first responders, etc., health state estimators hydration state, metabolic
state, fatigue, and cognitive state (see Friedl 2004) remain elusive using non - invasive sensors. From a military combat casualty care perspective, lives can be saved if remote monitoring can detect loss of blood (Rickards et al. 2008). Similarly, from a diabetes management point of view, the ability to estimate and guard against hypoglycemic shock is a critical step on the path to an artificial pancreas (Hoshino et al. 2009). "

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Cheers, Neal

+1 mph Faster

A valid point. I'm prepared to consider my view somewhat having taken on board others opinions here.

I assume Noakes view is that drinking to thirst is safe advice as drinking to thirst will not let you die of dehydration but drinking too much can kill you.

However, there are situations which arise when racing where I can see it being awkward, or tactically disadvantageous to only drink when thirst kicks in. Suppose thirst kicks in, you take a bottle and you get jogged and drop it. Do you lose time and go back for another? Staying a little ahead of thirst would mean you can relax and take a bottle further on with no loss of time.

Suppose a rival makes a break to take distance out of you just as your thirst kicks in and you have to decide to take the drink or go without. Being a little ahead of thirst gives you an option, an insurance policy.

I don't see the harm in some forward planning but you must be careful not to over drink.

Noakes may be going too far to one extreme to combat what he feels is a real danger of drinking too much.

On the other hand would going thirsty for a while be detrimental to performance?

I find it almost impossible to drink when running. I might get a drink in on the bike just before the run. I would rather do that before I'm thirsty, half a pint of liquid isn't going to cause a problem, but taking half a pint every few minutes would, so it's all about common sense and balance.

I still think drink to thirst is best advice for most sports and events and for most people even in an Ironman or a double marathon or 12 hour or 24 hour event. Perhaps if you are looking to shave a few seconds here and there it might be a tactic to take on some liquid on the bike to limit any liquid you need to take on the run which might slow you down.

However the longer the event the more danger of over drinking if you drink ahead of thirst, so Noakes advice to drink to thirst is sound.

On the very rare occasions I have taken on liquid ahead of thirst I've needed to urinate soon afterwards, so thirst works fine for me. All drinking in advance of thirst does is cause discomfort and wasted time urinating.


But I'm prepared to accept drinking to thirst might not work for those who have a genetic fault or have suffered some sort of illness which has damaged their thirst mechanism. Perhaps this is some sort of illness which has gone undiscovered.
Noakes has found the thirst mechanism is highly individual.

But, when people claim their thirst mechanism does not work properly and fails to make them drink enough, are they in reality getting dehydrated to the point performance is affected? Are they so used to, and so conditioned to permanently be slightly over hydrated, they mistake what is perfectly normal and acceptable as dehydration?

I think it is also a mindset. The athlete believes his performance will suffer if he doesn't drink enough so he drinks before he is thirsty. He has become so dependent on gadgets, so dependent on the clock, power meters, heart rate, counting calories, unnecessary quantification of every element of his training, racing, diet and 'fuelling strategy' he has lost confidence in his own brain and body. He has lost the ability to 'feel', lost the ability to trust his thirst mechanism.

It appears that what is needed is a more accurate method of diagnosing hyponatremia which is a condition that occurs when the level of sodium in the blood is too low.

I'm pretty sure that the level of sodium isn't the issue, it's the concentration. Then, the rest of this sentence makes sense.

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Take a short break from ST and read my blog:
http://tri-banter.blogspot.com/

You make some really excellent points here Trev, and they are well taken. You are right too-- overhydration kills, and the worst underhydration usually does it maybe impair performance. I think it is important for athletes to practice and study their own fluid balance, weighing themselves before and after long hot workouts, and getting in touch with how much they should drink. You may find this interesting, although it was pretty in depth...

http://journals.lww.com/cjsportsmed/Fulltext/2015/07000/Statement_of_the_Third_International.2.aspx

Hello shacking and All,

Thanks for posting the 'Statement of the Third International Exercise-Associated Hyponatremia Consensus Development Conference, Carlsbad, California, 2015'

http://journals.lww.com/...International.2.aspx

The conference also endorsed the 'drink to thirst' primary recommended fluid intake strategy to prevent symptomatic EAH.

Excerpts:

"The reported incidence of asymptomatic EAH has ranged from 0%30,53 to 51%54 immediately post-race. In a study of an ultramarathon, 67% of the participants were hyponatremic (asymptomatic) at some point during the race, but only 27% finished the with serum [Na+] <135 mmol/L (40% self-corrected prior to finishing the event).11 The highest reported incidence of asymptomatic hyponatremia post-race has been consistently noted in 161-km ultramarathons, in which the reported incidence of EAH has ranged between 5% and 51%.18,54–56 The incidence of asymptomatic EAH in Ironman triathlons in different environments has been reported to range from negligible10 to as high as 18%57 and 25%.19 In studies on endurance cyclists the incidence of asymptomatic EAH has ranged from 0% in a 720-km race30 to 12% in a 109-km race.15 In a 26.4-km swim, 17% of swimmers developed asymptomatic hyponatremia.32The reported incidences at the standard marathon distance run (42.2 km) have ranged from 0%53 to 12% to 13% of race finishers.28,58Additionally, asymptomatic hyponatremia was observed in 33% of premier league UK rugby players following an 80 minutes rugby competition59 and 70% of elite rowers during a 28-day training camp.60"



"Symptomatic EAH is rare and occurs with considerably less frequency than asymptomatic EAH, but complications associated with EAH have led to at least 14 athlete related deaths since 1981.28,38,47,50,61–69 Symptomatic EAH generally occurs as an isolated case or in small clusters during or following endurance events with participants reporting to the race medical facilities or to hospital emergency departments within 24 hours after participation. In general, participants seek treatment for a constellation of symptoms ranging from feeling unwell to convulsions. Clusters of cases have occurred in military training exercises, marathons, Ironman triathlons and ultramarathons. The incidence of symptomatic EAH has been reported to be as high as 23%57 and 38%70 of athletes seeking medical care in an Ironman Triathlon and an ultramarathon, respectively, but most endurance events report no cases of symptomatic EAH, especially at the marathon distance and below.


Two studies have examined large compilations of data to help define the incidence of symptomatic and asymptomatic EAH. 55,71 In the first study of 2135 athletes from 8 endurance events ranging in length from 42.2 to 161 km,71 the incidence of symptomatic EAH was 1% (compared to 6% with asymptomatic EAH) among study participants. In the second study of 669&#8201;161-km ultramarathon runners,55,72 only one case (0.1% among study participants) of symptomatic EAH presented during the 5-year sampling period (compared to 13% with asymptomatic EAH), but considering the total number of race participants over this time period, the actual incidence of symptomatic EAH was approximately 0.06%.Symptomatic EAH has also been reported in hikers73–75 and military personnel. 75–77 Symptomatic EAH accounted for 16% of Grand Canyon hikers seeking medical care for exercise-associated collapse or exhaustion from May 31, 1993 through September 31, 1993 providing an estimated incidence rate between 2 and 4 per 100,000 persons. 73,78 Furthermore, suspected hyponatremia was found to account for 19% of non-fatal suspected heat-related incidents in the Grand Canyon National Park from April through September during 2004 through 2009 hiking seasons. 74 In the US active duty military, the annual incidence rate of hyponatremia from 1999 through 2012 has ranged from &#8764;4 to 13 cases per 100,000 person-years (averaged 6.7 cases per 100&#8201;000 person-years). 77


However, this incidence is probably inflated as the data were derived from a medical coded database that does not have a specific designation for EAH and likely includes hyponatremia from both exercise and non-exercise related conditions. Alarmingly, symptomatic EAH is now being reported in a more diverse set of sporting activities. For instance, symptomatic EAH has been reported in shorter distance endurance competitions, such as a half marathon79 with slower finishers completing the distance in 2 to 3 hours and a sprint triathlon with slower finishers taking approximately 2 hours to complete.80 In addition, EAH has been reported in US professional and college American rules football players40,41 and has led to the deaths of 3 US high school football players between 2008 and 2014.63,64,69 Symptomatic hyponatremia has also been reported in a 48 year old lawn bowler who was heterozygous for the Delta F508 cystic fibrosis (CF) mutation, although it is unclear if complete genetic analysis for all possible CF mutations was performed,81 a 34 year old woman following a Bikram Yoga session82 and in a 39 year old woman following a 2 hour workout including tennis and weightlifting.83 Cases of symptomatic EAH have also been induced in 2 separate laboratory studies involving low intensity exercise conducted in high ambient temperatures.84,85 Deaths from symptomatic EAH have occurred in a 25 year old male police officer participating in a 19-km bicycle training ride68 and at least partially contributed to a case of fraternity hazing involving a male pledge performing calisthenics.67 It is likely that other cases of symptomatic hyponatremia have either not been recognized or reported."

"When fluid intake matches or even slightly exceeds sweat losses, the ingestion of sodium-containing sports drinks can attenuate the rate of fall of [Na+] over the course of 2 hours of continuous174 or intermittent85 cycling and ¡&shy;4 hours of running.89,175 However, it is critical to emphasize that sodium containing sports drinks, which are hypotonic, will not prevent EAH in athletes who overdrink during exercise, as all sports drinks have a significantly lower [Na+] (10-38 mmol/L) than serum (¡&shy;140 mmol/L). The dilutional effect of volume excess overwhelms any positive effect of sodium and electrolytes in sports drinks.90 Therefore, while modest salt replacement is likely not harmful and has been associated with significant increases176 or no change14,177 in serum [Na+] during competitive field events it will be of modest to no benefit in situations where excess fluids are being consumed. The potential detrimental effects of excessive sodium supplementation are not clear.72,178"


[Emphasis added]


I previously incorrectly believed that drinking a sports drink with a large measure of salt provided some protection against EAH (exercise associated hyponatremia) ....

....... based on this report I will review and modify (as required) my hydration and nutrition procedures ...... and be very careful to not over hydrate during exercise .......... or for a day or so afterward.

Next gadget might be a serum Na realtime read out next to the Watts and cadence.

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Cheers, Neal

+1 mph Faster

I appreciate everyone's enthusiasm and expertise. There is one take home message that I want to make sure everyone understands. We as a whole do not need to concern ourselves with hyponatremia that is asymptomatic. Also, hypovolemic hyponatremia (dehydration) is easily correctible (oral and IV fluid replacement). Yes, I also realize people can die from dehydration too. Our main danger we need to address in terms of education is hypervolemic hyponatremia, which causes brain swelling, pulmonary edema, and sometimes death when not recognized.
Too often, the conversation turns to a discussion of all three scenarios simultaneously which confounds the important safety issue. Also, journalists and lay people without a proper understanding of physiology confuse the 3 repeatedly. This is frustrating.
We know one thing-- that drinking to thirst will prevent fluid overload. This is a great recommendation for recreational athletes, and even marathoners whose race will end in under 3 hours. It may even suffice for a significant proportion of ultrarunners based upon their own body characteristics (weight, sweat rate, etc) Unfortunately, drinking to thirst is not an appropriate strategy for competitive amateur and professional athletes who compete in hot conditions for over 4 hours at a time, such as in an Ironman race.
Luckily, learning how much and how often to hydrate is a learnable skill set obtained through practicing in the heat, by weighing before and after, and noting how conditions and hydration strategies affect weight. What continues to irk me is the idea that we are all cast of the same mold, and that there is only one truth that we can apply to everyone. I am glad Dr. Noakes has run ultras and has had his boots on the ground, but I reject the idea that "drink to thirst" is an undeniable, universal law.

An excerpt from the 2015 Consensus Guidelines states:
For those doubting the protective effect of our thirst sensation or concerned about the risk for dehydration, another simple protective strategy is to estimate hourly sweat losses during exercise and avoid consuming amounts that are greater than this amount during endurance or other athletic events.13 This is facilitated by serial measurements of weights during and after exercise with the goal to maintain weight or even finish exercise with a slighter lower weight. A concern is that this technique may be more time consuming and less likely to be followed by casual athletes. This strategy may be particularly attractive to certain sporting events such as football where sideline scales can easily be available to guide fluid intake.

This is basically what I wrote in my first post on the front page article about the Frankfurt athlete death.

During today's workout I weighed in before the ride in 32C heat and 70% humidity. Starting weight was 140 lbs. Drank 750 mL during the hard 3 hour ride (~2900 ft vertical) and ended the ride at 138.5 lbs. drank 200 mL more of water and ran 5K by which point the temps had gotten a touch hotter. In only 25 minutes on the run trail which had turned to a sauna I lost one more lb on top of the half pound I would have "gained" from the 200 mL water intake. So ended up at 137.5 lbs off 3.5 hours of training with 1L intake. The quick math on that is 1L intake (which would be 1 kilo or 2.2 lbs), so lost a total of 4.7 lbs in this temp given the intake. Also keep in mind that 2 lbs should be automatically lost because as I am working through the glycogen stored on my body I should lose a few lbs anyway with no safety issue....so really it's only around 2.5 lbs of fluid actually lost over 3.5 hours on a crazy humid day. So the replacement rate is around 350 mL per hour, maybe 400 mL but not that much more.

Going through this exercise in a variety of conditions and you kind of end up with the safe range that you can operate in without overdrinking and it takes out some of the guesswork on 'drink to thirst'. If you know your loss rate, you can safely stay 'close enough' and not go too far over or under.

Personally my thirst mechanism is not that great especially in the first 2.5 to 3 hours of any outing (training or racing) on the bike. On the run, I'll notice thirst much earlier.

Excellent writing and an excellent contribution-- Thank you!

very timely article today on cbc.ca:

http://www.cbc.ca/news/health/hydration-myths-debunked-in-5-easy-sips-1.3155705

http://www.brocku.ca/brock-news/?p=33651

This particular research involved 11 trained racing cyclists who wore IV drips while riding stationary bikes under competition-like conditions. Some cyclists had IV drips containing a saline solution to replenish fluids lost through sweat, but others had IV drips that were shams, providing no rehydration at all. - See more at: http://www.brocku.ca/...-news/?p=33651#.dpuf

“What we’ve found was really novel. Even at up to three per cent body mass dehydration, no impairment was seen in exercise in the heat.” - See more at: http://www.brocku.ca/...-news/?p=33651#.dpuf

If power output is not affected at up to 3% dehydration, then you will go faster when dehydrated up to 3%, because you weigh up to 3% less.