jnbacon

The NY Times has an article (warning: requires subscription) describing a study published in the New England Journal of Medicine (abstract of study) that found that drinking too much water during intense exercise lead to hyponatremia, low sodium levels, in 13 percent of the runners tested. The research was conducted in part because medical teams at races were finding high incidences of hyponatremia, and the researchers wanted to learn more about the types of racers who were at risk. The study found that slower (i.e. non-elite) athletes were more likely to get the condition, largely because they were taking the time to drink more fluids. Here's an extended quotation. It cites runners because that's where much of the problem lies, but cyclists are also at risk, as mentioned later in the article.

"Hyponatremia is entirely preventable, Dr. Adner and others said. During intense exercise the kidneys cannot excrete excess water. As people keep drinking, the extra water moves into their cells, including brain cells. The engorged brain cells, with no room to expand, press against the skull and can compress the brain stem, which controls vital functions like breathing. The result can be fatal.

But the marathon runners were simply following what has long been the conventional advice given to athletes: Avoid dehydration at all costs.

"Drink ahead of your thirst," was the mantra.

Doctors and sports drink companies "made dehydration a medical illness that was to be feared," said Dr. Tim Noakes, a hyponatremia expert at the University of Cape Town.

"Everyone becomes dehydrated when they race," Dr. Noakes said. "But I have not found one death in an athlete from dehydration in a competitive race in the whole history of running. Not one. Not even a case of illness."

On the other hand, he said, he knows of people who have sickened and died from drinking too much.

Hyponatremia can be treated, Dr. Noakes said. A small volume of a highly concentrated salt solution is given intravenously and can save a patient's life by pulling water out of swollen brain cells.

But, he said, doctors and emergency workers often assume that the problem is dehydration and give intravenous fluids, sometimes killing the patient. He and others advise testing the salt concentration of the athlete's blood before treatment.

For their part, runners can estimate how much they should drink by weighing themselves before and after long training runs to see how much they lose - and thus how much water they should replace.

But they can also follow what Dr. Paul D. Thompson calls "a rough rule of thumb."

Dr. Thompson, a cardiologist at Hartford Hospital in Connecticut and a marathon runner, advises runners to drink while they are moving.

"If you stop and drink a couple of cups, you are overdoing it," he said.

Dr. Adner said athletes also should be careful after a race. "Don't start chugging down water," he said.

Instead, he advised runners to wait until they began to urinate, a sign the body is no longer retaining water. " GINA KOLATA, NY Times, 04/14/05

jeff-o

What happens when athletes drink sports drinks in the same amounts as water? Do the added salts draw water away from cells?

mrog71

It doesn't require registration, it just requires www.bugmenot.com

jnbacon

I'll take a (non-expert) stab at this. In order to draw water out of the cells, it takes a concentrated salt solution. So, if the sports drink has a sodium level that is lower or equal to that of the person's blood, it will simply exacerbate the condition. My guess is that most sports drinks don't have sodium levels that are higher than blood's sodium levels, because they would taste salty.

bostontrevor

Gatorade tastes salty. The fact that you need to dilute it to achieve an isotonic solution tells me that in its undiluted form it's saltier than blood.

Personally, I try not to head out with just water. I figure there are other things that I'm using up besides water, so I should have some sort of sports drink (be it an -ade or just good old OJ & H2O) to replace some of that. This only adds weight to that rule of thumb.

terrymorse 

Gatorade tastes salty because it is isotonic. Blood also tastes salty, as does sweat.

alanbikehouston

A woman died after the Houston Marathon two years ago. She had been worried about dehydration, so began drinking about 12 ounces of water per hour two days before the race. She grabbed water at each water station. During the last hour of the race, she began to get dizzy and unsteady, which she thought was a sympton of dehydration. She increased her water intake, and collapsed.

When she got to the hospital, they also assumed she was dehydrated, and were going to give her an IV. Someone figured out, too late, she was overly hydrated.

The Houston Marathon has moved its water stations further apart, to make it more difficult to overhydrate. They have also tried to educate folks on water intake being related to size. The 100 pound female had been consuming enough water for a 200 pound man, not realizing that the "guidelines" on water intake are based on some mythical "average" person.

It is interesting that the medical treatment for "over hydration" involves taking salt. Forty years ago, my coaches used to force me to take salt tablets on hot afternoons. They had no clue why we were taking salt tablets, just something they had learned from their own coaches forty years before that.

And, Gatorade, a very well testing sports drink does contain a bunch of sodium...maybe those Gatorade folks are related to my old coaches.

dc70

What a bunch of crap. Geez, one day something is vital and good for you..the next its too risky, no good 'They Say'...Is it any wonder the general public loses more and more respect for these so called experts? Almost any good athlete knows, or should his or her own body, and its needs. Do what suites it best. Uhg...

Spoof:
Ah....yea hi, we are the experts at XYZ medical and/or University...and we just found out through exhaustive study..using your tax dollars..that breathing too much clean air is NO good for you! So, ah until we know more...stop breathing so much. Thank you.

'nother

That sounds like an awful lot of water to consume. I can barely keep up getting 8 every couple of hours. Is this really a danger to the average non-fanatical person? I'm skeptical.

'nother

Very likely so . . . you know Gatorade is the brainchild of a research team at the U. of Florida (Gators), who mixed up this concoction of water + salt + sugar + flavor, around 1965 or so?

I remember those bottles of Morton's Salt Tablets . . . vile yellow things. uggh. Woudn't think of touching them these days, with high blood pressure to manage . . .

terrymorse 

Define fanatical. It's not that hard to get hyponatermia severe enough to make you sick on a hot ride that lasts several hours. I've experienced it myself once, about 7 hours into the Climb to Kaiser. I felt really bad and had to lie down on the ground for an hour before continuing. I've been on group rides twice where other people have gotten it. The symptoms are debilitating. I hear you can sweat out up to 2 grams of salt per hour -- it doesn't take long at that rate to run through your body's salt stores.

Nowadays, I carry Endurolytes, which are basically fancy salt capsules. They can make the difference between finishing a ride or ending up in the ER.

jnbacon

It was the non-elite athletes that got this condition, the ones who (perhaps) weren't fanatical but who were slow enough to stop at the water stations, and, perhaps, were more likely to be unaware of the dangers of drinking too much water.

For me, a desert dweller who commutes in the summer, the lesson is to be cautious about how I hydrate and what I hydrate with, and to make sure I'm getting most electrolytes back in after/during long rides.

Rowan

jnbacon , from what you say, you're neither an elite athlete nor fanatical. How long have you been commuting without problem? Why should this be a problem for you now that someone has published a paper on elite athlete performance?

Most likely the hook turn by an errant motorist tomorrow morning will represent more risk to you than this.

It's *highly* likely that if you consume a far-Western diet, the normal salt intake in your food will more than compensate for the losses you sustain in your normal riding activity. If not, the commercial or mix-your-own drinks with salt *and* potassium will compensate.

The case cited is extraordinary and appears fanatical. She'd likely been told by some incompetent about this hydration process, and become religious about it. Now ... how many ran in the marathon?... and how many lived to finish with normal rehydration?

The problem with a case like this is that it diverts attention away from proper rehydration. In most cases, that rehydration comprises the said commercial or self-mixed combination of carbohydrate *and* salts that help prevent occurrences such as this.

People who are intent on doing long distance riding usually are capable of researching the issues through several means, including the internet to reputable specialist sites such as ultracycling, or through consulting personally with experienced trainers, or by experimenting on their own.

Hissy-fit posters here don't serve the situation at all. As pointed out on another parellel thread, hyponetremia is well known, but the more serious problem is dehydration, and is the one that needs to be dealt with as a priority. This hyponetremia issue only serves to put doubt into people's minds about their fluid intake... to their detriment.

Awareness of *both* issues is important. But I'd go with rehydration first... from my personal experience.

kf5nd

The really tricky thing is this...

You can only drink a solution which is isotonic (same salinity as blood) or less salty than isotonic... why? Because if you take a too-salty drink, water will be drawn into your stomach and gut by the salt, and you will dehydrate. And since we really can't drink more than about a quart an hour, we can't take in more than about 400 mg of sodium per hour in sports drinks (I think Gatorade is 100 mg per 8 oz).

But, if you're losing salt in extreme conditions (like where I live, Houston, 95 degrees and 90% humidity, and bright sun) then you lose 1000 - 2000 mg per hour.

You can't shovel in the salt fast enough to replace it.

If you take a quart of isotonic solution per hour, you're doing the best you can. At some point, you just have to know when to say, "Enough! These conditions are too harsh". The long-term answer is better conditioning, so you finish the event faster and hit the showers.

Rowan

I think you've hit the nail on the head. At some point (preferable BEFORE an event starts), people have to take responsibility for their preparation. Read any long-distance cycling forum, and there will be ample advice on what to expect with tough, hot and/or humid events.

Surely, research by a competitor and their coach also includes finding out how peers have performed in similar conditions. There might be variations in personal physiology, but, gee, the correlations with regard to conditions are remarkable.

Then, also, the same applies to normal (commuting, touring) cycling. If the conditions are overwhelming, who would continue without adequate salt and fluid intake? Or even ride at all?

One of the interesting themes that appears in accounts of long-distance cycling is a rider's yearning for a particular food. It might be something like potato crisps or pretzels with their high salt content. Or milk drinks because of their protein and fat content. Or it might be a pizza, with its cheese and pastry that provides carbohydrates and concentrated fats.

It's a matter of reading your body as much as anything else. Experienced long-distance riders learn that. It's as applicable to people who ride in unusual conditions such as high temperatures or humidity, or who have a high power output.

As an aside, for a long-distance *event*, or even a short cycling event in extreme conditions, there should be a responsibility on the organisers and coaches to recognise the symptoms of both dehydration and hyponatremia. They should be able to recognise the need to withdraw participants who are judged to be incapable of continuing without endangering their health. In most cases, it's because of dehydration.

Certainly, in events that I organise, dehydration is a primary concern, but delitirous behaviour can be interpreted in other ways, too.

Doctor Morbius

Hyponatremia can be a fatal condition. Please donate generously to our research today so that we may prevent this terrible affliction on future generations.



Does that kind of summarize what a load of crap this is?

jnbacon

The responses from Rowan and Dr. Morbius suggest that they think this was an alarm call -- likely caused by the bad choice of wording in the title of my post . The article and study, though, made no alarmist calls. The article reported on a carefully done study of an increasingly observed trend in intense events, that inexperienced participants who had been told to watch for dehydration were over hydrating themselves, and the study indentified likely factors, slow pace being one. The only changes being suggested were for the organizers of marathons and other athletic events, and for emergency rooms that are treating stricken athletes, and the primary change seemed to be to do a salinity test of blood. Not exactly a call to arms.

As to whether it identified a problem for me - I never said that I thought I had a problem. But it was new information (for me) about how the body works, and gave me insight into the observations I was making about how my body feels during and after my commute and training rides, especially in extreme heat.

Doctor Morbius

Nope. Actually, I was just being a wise ass. It happens from time to time.

The thing is there is so much conflicting information about what is healthy and what isn't that most of it just ends up doing more to confuse people than to help. Dehydrated, over-hydrated, whatever. Next there will be a study that states smoking is good for you. As a skeptic, I can't help but think that much of it depends on who will be footing the bill for the research.

No doubt people will be collapsing during the Boston Marathon Monday. Some will be from this some will be from that, most will be from lack of conditioning. Many of the people attempting this run have absolutely no business taking on something like that. It will be that day or the night before when they decide to "experiment" with their hydration levels. Stupid.

'nother

I guess fanatical to me is someone who monitors their fluid intake so closely to know that they've consumed 12 oz every hour, as the person in the story that alanbikehouston posted . . . which sounds more like it was caused by overconsumption of water rather than insufficient salt replacement. I guess that sounds like the same thing, but if she had been drinking, say, 12 oz every 2 or 3 hours prior to the event, would it have been an issue? Or was her amount of water intake sufficient, just not enough salt?

Count me among Doctor Morbius' "confused" I guess . . . it's just so counter to my own experience, I cannot relate. Sorry to hear you were "bitten" . . .

cbhungry

The upshot is this: The data supports drinking when thirsty. The data do not support drinking at all water stops. Drinking at all water stops puts one at risk for hyponatremia. This phenomenon occurs over time as someone stated, thus, the deconditioned athletes have more time to drink. High performers finish before they have time to drink enough.

"Did the study address any difference between runners who drank water and runners who drank sports drinks or other liquids with ion concentrations closer to serum?" as people have posed on this thread.



Sports drinks do not help here. To paraphrase in layman's term from a medical site.... think of a sports drink as having the same solute concentration as blood (isontonic) . When ADH (Antidiuretic hormone) is stimulated (which it is without going into complicated renal physiology) the urine concentration becomes at least twice the serum concentration. If we assume urine concentration is twice serum concentration, then it is also twice the concentration of the sports drink. If we drink in a liter of sports drink, we only urinated 500 ccs of urine to excrete the solutes (thanks to antidiuretic hormone being released). This leaves 500 cc of new free water - which dilutes the serum and lowers the sodium. The other problem with sports drinks is the glucose - which increases water absorption, making the sports drink more effective at increasing free water (and thus lowering serum sodium).

terrymorse 

The American College of Sports Medicine has a position paper on hydration:

• 500 ml of fluid 2 hours prior to exercise
• drink enough during exercise to replace fluid loss through sweat
• add carbs & electrolytes for events longer than 1 hour

They don't give an upper limit to the amount of hydration per hour, but I've seen other papers that recommend no more than 1 liter per hour. That's a lot to drink, I max out at about 750 ml. per hour.

Getting "bitten" by hyponatremia was not fun. I didn't even want to look at my bike for 3 days afterwards.