The Hype of Dehydration and Heatstroke

[W I S N E R !]

From The Science of Sport, one of my favorite sites.
http://www.sportsscientists.com/2013/01/dangerous-exercise-hype-of-dehydration.html

Interesting read, especially in the context of backpacking, which would typically be categorized as not strenuous (sorry, as hard as I know it can feel to some, it's not the same as racing a time trial or other high intensity pursuits).

The article raises the issue of underlying causes as well as personal perception; being made very uncomfortable by thirst or heat while simultaneously being in no actual physical danger.

It also makes me wonder about how effectively we have all been marketed to be drink and supplement companies.

I've always thought that overly complex hydration and nutrition strategies during average backpacking pursuits seemed a little silly in the face of athletes that can knock down 4:45 miles for 26 straight, lose 5kg of bodyweight in the process, not take a single sip or bite, and recover just fine.

[bjc]

Waterlogged: The Serious Problem of Overhydration in Endurance Sports
Timothy Noakes

The above is a pretty detailed look at the issue of hyponatremia or over hydration. While dehydration can be an issue, a lot of what we were taught as coaches and athletes may not be particularly accurate. It's a long book and extremely detailed, but Noakes is one of the premier exercise physiologists in the running community. Needless to say, the Gatorade sports science guys are not happy with his research.

[Roger Caffin]

> Needless to say, the Gatorade sports science guys are not happy with his research.

There are NO 'Gatorade sports science guys'. None. Contradiction in terms.
They are mainly marketing spin doctors with funny hats on.

Cheers

[bjc]

Roger,
I stand corrected and humbly so! And I agree.
BJ

[BlackHatGuy]

"There are NO 'Gatorade sports science guys'. None"

That's a bit harsh. Perhaps not now, but it was developed by researchers.

[Ken Thompson]

Go Gators!

I still like the lemon lime.

Though is has certainly changed since it first came out.

Heatstroke sucks. I don't recommend it.

Thanks for the link.

[Jerry Adams]

They had me drink Gatorade the night before colonoscopy

I do not like Gatorade

[spelt with a t]

Me neither, Jerry.

[Todd T]

"They had me drink Gatorade the night before colonoscopy

I do not like Gatorade"

Not anymore, I guess! :-)

On the other hand, I'd have given my eye teeth for Gatorade instead of the evil potion they made me drink.

[Anonymous]

"On the other hand, I'd have given my eye teeth for Gatorade instead of the evil potion they made me drink."

That they produce the same result makes one wonder about Gatorade. ;0)

[Franco Darioli]

I still see the idea that hikers need to continually sip from their water bladder a bit odd but if it makes them happy….

[Nelson Sherry]

Okay, I can't resist this one. . .
1) Marathon runners don't run marathons without drinking anything. They just don't drink nearly as much as they sweat out.
2) The linked article is about incorrectly attributing sudden death in sporting events to dehydration or heat stroke, not any suggestion that rehydration drinks are less than claimed.
3) I agree with the general direction of this thread that we, as a culture, are over excited about hydration and food chemistry in lower intensity, non-competitive sports.
4) For low intensity exercise in warm weather, gatorade provides people with a nice sugar drink that includes some electrolytes. Both sugar and electrolytes are helpful in keeping one going during exercise on a hot day. What's wrong with that.

Of course, from the standpoint of elite endurance performance, Gatorade is lousy because it isn't the best balance electrolyte mix and it is too concentrated, sugar based, carbohydrates that tends to bloat the stomach, slow digestion and cause vomiting. However, diluted Gatorade actually works pretty well for re-hydration, although there is plenty of better product out there. My favorite re-hydration strategy for lower intensity exercise, like backpacking, is to drink water and eat a balanced diet of various snacks that have some salt in them. Admittedly, during hot weather, some salts added to my water or taken as tablets can be helpful.

[HkNewman]

In my experience, a continuous stream of dehydration, heat cramp, heat exhaustion, and heatstroke victims probably keeps the preventative tips in the first aid books (civilian and military). Even "ultra-fit" can succumb since they are used to toughing it out (remember that competitive runner who died in the Grand Canyon a couple years back?).

Handling medical evacs was one of my deployment assignments so during the summer train-up one afternoon, I had a string of Medevac choppers waiting to pick up heat injuries (all ages) out of the field for these problems – they were from another southern state no less, so acclimation only goes so far. A couple of the older ones were never the same health-wise and didn't deploy. In warm to hot weather, dehydration is nothing to mess with (of course, sometimes you just get caught short on water).

ed: gram

[Bob Gross]

"However, diluted Gatorade actually works pretty well for re-hydration, although there is plenty of better product out there."

For decades now I have used diluted Gatorade on warm backpacking days. Sometimes it is 50% strength and sometimes only 33% strength. The powder probably is not the very best product on the market, but it is cheap, effective, and readily available. I tend toward a potassium deficiency, so Gatorade takes care of that. Alternatively, I could carry along a bushel basket of tomatoes or something. I think I will stick with the Gatorade powder.

–B.G.–

[Larry De La Briandais]

Having been very near heat stroke myself (not while hiking) it is nasty business that I don't want to repeat. I will error on the side of drinking to much.

I have also seen a young lady on the verge of heat stroke at the top of Nevada Falls in Yosemite. She had stopped sweating and couldn't lift her head without sever dizziness. She had drank only one liter of water on the climb from the valley to half dome and back. I think it is 17 miles round trip and she was 12 miles or so into it. While I can't say that she would have died from it had she not drank (I filtered water for her group) she easily could have from the fall had she attempted to continue. I don't think she would have recovered before dark without intervention.

While hiking the "secondary problems" can become a deadly problem. And if you can push though the initial symptoms, once you near heat stroke you don't feel bad anymore. The confusion alone is dangerous.

All that said, yeah, staying hydrated is over hyped. You don't need to have clear urine. I hate hydration bladders, a simple water bottle works great for me.

[Anonymous]

Bah humbug on Gatorade, i like Coconut water with a bit of salt, or Lemon powder mixed with water and a bit of salt and sucanat.

[Paul McLaughlin]

Comparing elite marathon runners to backpackers is not of much use. Those guys take about 2 1/4 hours to finish. Yes, they are doing something more intense, but it's very different. My general rule of thumb is that no matter how hard I'm working, if it's 2 hours I can drink before and after and all is fine.

A much better comparison is a full days work on a hot day on a construction site. I've done a lot of that. 8 hours in the heat swinging a hammer and hauling lumber around. And I've watched guys who were not drinking enough get very close to collapse. When you see a guy turning gray and getting wobbly, it makes an impression. So I drink plenty. And It's pretty clear that I'm not drinking too much, since on a hot day I'll drink 5 or 6 liters and still only pee maybe once. Of course, everyone is different. I sweat quite a bit when I'm active, so I need to drink quite a bit to replace that. You have to know your body to know what works for you in various different conditions.

A typical backpacking trip is not as intense as that for me, since it's not often 100 degrees in the mountains. So I would be drinking less than that when I'm hiking – although for the first couple days at altitude I'll drink a little more, as it helps with acclimatization.

The easy indicator is what my urologist told me after I had a kidney stone – you should be peeing every 2-3 hours during the day. If you need to go more often than that, you're drinking more than you need. If you go 6 hours without taking a leak, you ought to drink more.

[W I S N E R !]

I'm not sure how many people commenting here actually read the article which got me thinking about this, but here are a few points I found interesting. I see no reason why the underlying ideas behind them couldn't also apply to backpacking, though perhaps on a different time scale.
_____________________________________________________

"Similarly, there is no link between fluid loss and heatstroke. Human beings can safely lose big volumes of fluid without their body temperature shooting through the roof. Typically, in a marathon on a reasonably warm day, we lose about 2 to 3 L of fluid over many hours. Faster runners lose more – Haile Gebrselassie is reported to have finished his Berlin World Record 5kg lighter than at the start."

"Heatstroke is a viable candidate for the tragic deaths that sometimes happen, but it's a grossly overstated risk and those who diagnose any athlete's collapse or medical condition on a hot day as 'heatstroke' are also taking a lazy and possibly very wrong option. The reality is that heatstroke is a pretty complex phenomenon, and is likely to involve some kind of pathology. Once again, I'd draw attention to the difference between the perception of being hot and actually getting to the kind of dangerous temperatures that characterize heatstroke. We're not talking about feeling hot, uncomfortable and slowing down or stopping here."

"…But recreational athletes don't produce enough heat to develop heatstroke through normal muscle activity. Therefore, we look at alternative theories – either these individuals are failing to lose heat, or they produced excessive heat from unnatural means." (I personally wonder how much obesity and/or poor cardio are at work here creating "unnatural means").

"… So the key points from those case studies – there are 18 documented cases, I've only discussed three – is that the athletes who suffer REAL heatstroke most often are not exercising very hard, they're not in impossibly hot conditions, and they show 'abnormal' heat gain even after they've finished exercise, sitting out of the heat (in a bucket of ice, in one case). Clearly, there's something else going on, and heatstroke does not happen just because we run hard on a hot day."

[Todd T]

Good comments, Paul. I think very few of the things one learns from running marathons apply to hiking. I always tell backpacking beginners:

It's a trek, not a marathon.

That has implications well beyond hydration. Nutrition, for example: forget those silly gel packs–you need real food to hike 10 hrs/day for a week. And playing through the pain: you can't go home and take a week to recover–you've got to get up in the morning and go again, and the next morning, and the next. If you hit the wall, you don't get to fall out and hitch-hike to the finish line; you must get to a campable spot tonight.

All those things imply sustainable effort and steady intake of food and water. Trickle the calories and water in. Snack often to keep electrolytes up. Etc.

[W I S N E R !]

"…forget those silly gel packs–you need real food to hike 10 hrs/day for a week."

Explain that to Greg "Malto" Gressel.

_______________________

I think most people in this thread are mistaking heat exhaustion for heat stroke.
Yes, heat exhaustion brings you to a quick halt and makes you feel like you are going to collapse and die…except you don't die or have to be hospitalized. Not the case with heat stroke.

[Bob Gross]

I saw the difference first-hand when I was in Army training during the summer at Fort Polk, Louisiana (read: hot and humid). They picked a warm day for us to do our 15-mile road march. One guy collapsed around nine miles out. They dragged him off the road and into the shade, then rubbed his skin with cool water while they got him to drink more fluids. He was conscious, so they hauled him back to base. That was heat exhaustion. The second guy was too stubborn to quit, so he was going until about 12 miles out where he collapsed. They dragged him off the road and into the shade, but he was unconscious. His skin was hot and dry, so they were not able to revive him. Once he got to the hospital, he was revived, but he had some brain damage. That was heat stroke. Not good.

I think our goal here is to drink more fluids and maybe electrolytes so that we never collapse in the first place.

Too many hikers will try to cross the desert without carrying enough water (weight). You have to have the experience to know what works and what doesn't work.

–B.G.–

[W I S N E R !]

"I think our goal here is to drink more fluids and maybe electrolytes so that we never collapse in the first place."

But that's the crux of it.

The entire premise of the article I linked is that heat stroke (and death from it) and dehydration do not necessarily correlate. Too many examples of people dying of "heat stroke" too early in an event or race to have been dehydrated. Nobody critically dehydrates in less than 5K, yet people die from "heat stroke" in the beginning miles of events on a regular basis.
In addition, there are plenty of cases of death and illness attributed to "heat stroke" that occur when it's not particularly hot and the victim was not exerting themselves very hard, thus leading to the question of how many of these supposed "heat stroke/dehydration" cases are actually due to some other issue.

This article is not arguing that heat stroke and dehydration do not exist; it's saying they are too loosely used to describe medical emergencies people are having that could have entirely different causes.

[Dan @ Durston Gear]

Great thread going here. This is something I've been meaning to get a better understanding of.

Perhaps someone can offer some insight/diagnosis on my situation last August. I planned a 1 night 60 miler that consisted of 15 miles one evening and then 45 miles the next day. The second day I hit the trail at 6am feeling good. It was a warm day and I was on a quick pace, so I sweating decently. I was trying to drink water, but I was probably falling behind. Then I got to an uphill forest fire burn area that offered little shade, which left me exposed to the mid day heat (full sun, 80 F) at the same time I ran out of water (poorly planned). This section was about 5 miles and I couldn't find my hat before the trip, so I felt like I was withering in the sun. I started to get a headache, which isn't that abnormal for me. I was sweating quite a bit – I remember marvelling at all the white sweat stains on my shirt and pack.

Anyways, in the late afternoon the headache remained and I started getting nauseous but forced down some water. All had been eating that day was energy bars and a tiny bit of jerky. I realized I was probably low on electrolytes so I finished the salty jerky, but it wasn't much. Even though the day cooled after dinner I still felt really hot and I was getting muscle cramps. My hands would clench and I couldn't release them – first time that had happened to me. By 5pm I really felt like crap: headache, nausea, overheating. I pushed on for a couple more hours and called it an early night (8pm) after ~35 miles. In camp I tried to sip water but I puked it up. The evening had cooled off but I was hot, so I laid naked in my tent with my heart racing. That was the weirdest part – my heart was probably up around 120 and it wouldn't slow down. I realized I could keep water down if I just had a wee bit and waited 20 minutes, so I worked on hydrating that way. I figured the biggest problem was maybe electrolytes, so I opened a foil pouch of tuna and drank only the salty brine (way too nauseous for food). I laid there barely sipping water from 8pm to probably 2am with my heart rate up for the first ~3-4 hours. The next morning I got up around 7am. I didn't feel so great, but I wanted to finish that last 10 miles before the heat of day.

So is this standard dehydration/low electrolytes? Or something else? For me the weirdest part was laying there while my heart was cruising along and refusing to come down. I heard that when you're low on water, heart rate can elevate to pump blood to help with cooling the body, so perhaps it was dehydration plus some overheating?

[jscott]

Dan: this past winter I went nordic skiing pretty hard for three days. Highish altitude, cold dry air and a stove in my cabin at night. On the fourth night I woke up at 1:30 with my heart racing and erratic. It didn't stop. I ended up in the ER and was cardioverted–electric shock to the heart, not fun–at which time I reverted to normal rhythm. Docs called it idiopathic, which means they don't know what caused it, but the best bet was dehydration. Very very scary.

So I just bought a steripen and will carry it along with a collapsible nalgene in my GG belly pack. This is to make it as easy as possible to drink water during the day during my hikes.

You don't want this to happen for a ton of reasons, but one more is that now there's a higher likelihood of recurrence. Also, apparently this sort of racing/atrial fibrillation (did you have that?)often onsets at night while you're sleeping.

It never occurred to me that I was overdoing things; in fact I felt great for the three days of skiing. But I live at sea level and ski at 7,000 feet. Age is catching up to me. Now I have to watch things.

Scary, no? I bet that you'll remember this and not do that hike again.

[W I S N E R !]

Both scary stories.
Jeffery, your experience is sort of what the article is talking about. The author raises the idea that many people are actually having some sort of cardiac event during exercise. Since the cause of the cardiac event is hard to pinpoint and could have to do with some existing pathology, a lazy answer is that it must have been due to dehydration or heatstroke, which both can present many of the same symptoms as a heart issue.
But if your bodyweight wasn't compared before and after the event and no actual tests on your fluids were done, how would anyone know that dehydration had anything to do with it beyond simple speculation?
Same goes for heatstroke; unless your core temperature is being monitored, most serious cardiac issues would present the same symptoms that heat stroke would.

But hey, I'm no doctor, (was a former working EMT with wilderness first aid training)
but I find it an interesting topic.

Sort of scary, because there have been many studies in recent years on endurance athletes and sudden cardiac issues or lasting damage supposedly done through endurance sports.

[Author]

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