heat acclimatization

That appears to be targeted at marathoners, which makes me wonder whether it’s relevant for hiking/backpacking. Marathoners learn to be completely spent at the finish line, just a few hours after starting, and knowing they’ve got the whole next week (or month) to recover. Backpackers go all day, day after day. Does that make a difference w.r.t. heat training?

I just moved to Chico from Humboldt ;) Now 60 seems chilly.

In my experience, after I hike in the heat a few days, it’s much easier

I think the information in that article is relevant to backpackers

It says if you don’t drink so much while exercising in the heat it helps you acclimatize.  I don’t know about that.  That may be controversial.

It says to acclimatize you want to get your core temperature up about a degree.  It also says this can be very dangerous.  If you want to be an elite marathoner, maybe this would be good but under supervision to make sure you don’t get too hot, and to resuscitate you if you do get too hot.

It also says that if you acclimatize to heat like they say, it will help your marathon time even if it’s not hot.  They also say acclimatizing to altitude can do the same, but altitude isn’t as effective.

We have something like this every year, here in Sydney. Summer time temps can go over 40 C, while overnight temps in winter can be below -2 C. It take a week or two each way to get used to the changes. But you do. We go running every second morning.

Cheers

I can’t imagine how dehydrating on purpose for any length of time can be healthy. Would anyone recommend NOT drinking water while backpacking in the heat in order to ‘acclimate’?
running in heat, then hitting the sauna, all while NOT drinking water seems like a bad idea. I suppose they know what they’re doing (?).

CAN one ‘acclimate’ to being dehydrated? Wouldn’t it simply be better to stay hydrated?

I agree that sounds like a bad idea

You’re not acclimatizing to dehydration, but if you become dehydrated your body will get into a particular state, and if you’re exercising, you will acclimatize to the heat better

I wonder if anyone else has any experience with that or if it won’t work

This would be useful if you were going on a backpack trip in heat, and you wanted to acclimatize ahead of time.  Exercise in heat before hand a time or two.  Don’t drink alot of water while you’re exercising.

How unhealthful is getting dehydrated?  Obviously, you can get heatstroke or whatever but what if you just get mild dehydration?

All this begs the question of what is ‘dehydration’?

As you can imagine, during a hot day the amount of ‘spare’ water in your body varies as you sweat. If you go for a run and sweat a bit, you will equally lose water. This does not mean you are now dehydrated. In fact, a lot of what is written about the ‘need to drink’ is medical crap. It is perfectly normal for your ‘hydration’ level to vary during the day, and there is no harm from this.

Where you can come to harm is from drinking too much. This is known as hyponatremia, and athletes have died from it. It can be dangerous. Here in Oz it can be quite hot during the day, but by and large we do not walk along sucking at some bladder to ‘stay hydrated’. It is in fact bad practice, driven mainly by marketing.

When out walking, Sue and I will have a cup of coffee at morning tea time. We may or may not even drink at lunch time. If it is a long day we may have coffee at afternoon tea time, although we often don’t bother. And we have been doing this for decades.

Cheers

Roger and I have disagreed over this before.

In my home setting of the Sierra, it can get into the 80’s or more even at elevation. I think elevation plays into this as well. If you’re climbing 3000 feet to a pass at 12000 feet while carrying a pack at 85 degrees F,  having a drink or two on the way is a good idea. You’re certainly not at risk of hyponatremia. You WILL be sweating a good amount.

But running in heat and then hitting a sauna without taking any water still seems like a bad idea. Anyway, I’m confused as to the point of it all. That level of (de)hydration can’t be optimal for racing. Do these runners intend not to drink water during their races in very hot weather? Why not?

“Where you can come to harm is from drinking too much. This is known as hyponatremia, and athletes have died from it. It can be dangerous.”

True enough, but you can also come to harm from not drinking enough.  Athletes, and others, have died from that condition as well.  Knowing your personal limits is key to staying alive in extreme heat at either end of the fluid intake spectrum.  Personally, I would recommend erroring mildly on the side of taking in  too much fluid.  Your kidneys will thank you.  Dehydration is an insidious condition, and by the time it is starting to become physically obvious, you are too mentally impaired to deal with it.  I speak from personal experience that got me in serious trouble on two occasions.  Like so many problems, this is one best avoided in the first place, because once things start to unravel, you are in deep doo doo.  Better to slow down and drink a little too much when hiking in hot weather, especially at altitude.  Desert rats like Roger, Nick, and others will scoff at my words, but I am not addressing them here.

Top marathoners drink little why they are running, although many of them have been known to collect the drink bottles along the way and pour them over their heads! It is normal for them to end the marathon quite ‘dehydrated’.

It is better to leave the stomach alone when running, in order that your blood supply focuses on pumping to the muscles. Diverting blood away from your muscles to your stomach is not a way to win races.

The sauna bit? I have no idea. Off the cuff, it just seems like a fetish or hobby horse to me. We do have a cool shower after a morning run in hot weather, to wash away the sweat and cool down a bit.

Cheers

A military trial was once run (poor grunts). Soldiers were marched in (I think) desert conditions until they dropped from dehydration or more likely heat exhaustion. Yes, it was done under medical supervision. They were then given shade and water and their recovery was timed. In general they were back at full (military) performance levels in about 15 minutes, with no evidence of any harm.

Now, before anyone goes spare about this, let me emphasise that I am NOT minimising the significance of heat stress and heat stroke. These are real and the latter can be serious. BUT, you can deal with them and fully recover very fast if you know how. Actual hydration levels don’t have a real lot to do with these conditions: you might be as well advised to pour the (hopefully cold) water over the back of your head and neck, slowly. That is a serious bit of advice btw: doing so cools the top of your spinal column and the motor centres in your head.

Cheers

.https://www.webmd.com/fitness-exercise/heat-exhaustion#1

“Heat exhaustion is a heat-related illness that can occur after you’ve been exposed to high temperatures, and it often is accompanied by dehydration.

There are two types of heat exhaustion:
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• Water depletion. Signs include excessive thirst, weakness,headache, and loss of consciousness.
• Salt depletion. Signs include nausea and vomiting, muscle cramps, and dizziness.

Although heat exhaustion isn’t as serious as heat stroke, it isn’t something to be taken lightly. Without proper intervention, heat exhaustion can progress to heat stroke, which can damage thebrain and other vital organs, and even cause death”

Roger wrote his post with an important caveat talking about this stuff. He’s not advocating for heat stroke/dehydration.

But why go there? Before you reach the point where you NEED to recover, drink some friggin water and eat some chips. Jump in a lake. How hard is this?

I totally agree with that. If you become dehydrated it can be dangerous.  Make sure and drink plenty of water.

But, that is consistent with the idea you can more quickly acclimatize to heat if you don’t drink water during the acclimatization period.  If you do this you have to be careful to avoid heat exhaustion.  I’m just taking the word of the author that this actually works.  And I’m not suggesting that anyone do this, but it would be interesting if anyone else has experience with this.

If this actually works, it would be useful for a backpacker about to do a hot trip.  Beforehand, you could acclimatize as quickly as possible – exercise in heat maybe just one day, don’t drink a lot of water until you’re finished, be mindful of heat exhaustion symptoms, that would acclimatize better than if you drank a lot of water while you were exercising in the heat.

And, the article was more aimed at elite marathoners trying to get the last bit of performance advantage.  It also said that marathoners sometimes acclimatize to high altitude beforehand to get a little more performance for a race, but it said that acclimatizing to heat is more effective.

And regard Roger’s grunts, if you become mildly dehydrated, you can quickly recover by drinking a bunch of water and resting for a while.  Occasionally you read about a “grunt” that died due to heat exhaustion.

On my last trip I screwed up and forgot to drink much while exercising in heat, sweated a lot.  My urine was fairly dark colored.  I was exhausted.  I drank a couple pints of water and rested for a while and was much better.  I drank maybe 4 more pints over the afternoon and evening and my urine became only slightly yellow.  I seemed to be totally recovered.

The next day I drank a lot and stayed hydrated, but there was one point where I was maybe more exhausted than the previous day when I was dehydrated.  But it was steep 2500 feet elevation gain and warm.  I just slowed up a little and was fine.  Doug went ahead at a faster pacer and checked out the lake before I got there.  Maybe I had actually not fully recovered from the previous day’s dehydration.

“It is better to leave the stomach alone when running, in order that your blood supply focuses on pumping to the muscles. Diverting blood away from your muscles to your stomach is not a way to win races.”

A huge +1 to this comment.  It is an often overlooked physiological reality that leads to reduced performance, not only in running, but also in any physically demanding activity.  Personally, I have long applied this principle when backpacking as well as when I was racing, although I am in a small minority to do so in the latter activity.

“These are real and the latter can be serious. BUT, you can deal with them and fully recover very fast if you know how.”

Up to a point.  The real danger is that the indications can manifest themselves very insidiously and get to the point where your mental faculties are impaired to the point that you no longer can act rationally.  At that point, you are in deep, potentially fatal, trouble.  I had that experience in two distance races in very hot weather, one a trail marathon, the other a 50 mile ultra.  In both cases I was diagnosed as massively dehydrated, and the treatment was intravenous rehydration with an electrolyte solution.  I have to disagree with Roger here about dehydration not being relevant.  Your body cools itself primarily by evaporation, and this requires a constant supply of water to maintain the process.  Yes, you can get away without it for awhile, but you will soon need to reestablish your fluid balance to continue the process.  How long you can continue without fluid replenishment depends on many factors, such as your conditioning, ambient temperature, and intensity of the activity.  Some will consider this to be “medical crap”, but in my case rapid administration of fluids manifestly saved my life.  Rather, I consider it to be a demonstration of applied medical knowledge.

“But why go there? Drink some friggin water and eat some chips. Jump in a lake. How hard is this?”

Indeed.  The problem is when your judgment insidiously becomes impaired and you don’t realize that that is what you need to do. Far better to err on the side of caution and drink judiciously before hand, particularly in hot weather AND/OR at altitude.  I find it not amiss to add 1/4 tsp of NaCl, about 300 mg, to a liter of water in extremely hot weather, such as that found on the more strenuous East Side Sierra passes, to avoid possible hyponatremia.

wouldn’t ‘acclimating’ before a hot trip by drinking less water result in your going into the trip already water poor in terms of body cell storage etc.?

I always heard that it’s a good thing to drink MORE water for several days before a large exertion in order to insure that your body cells and organs were well hydrated.

Of course, running a marathon in extreme heat isn’t about being healthy. And training to stress your body to the point of collapse like the soldiers did also isn’t about health.

“The real danger is that the indications can manifest themselves very insidiously and get to the point where your mental faculties are impaired to the point that you no longer can act rationally.”

that’s like hypothermia

yeah, the few times I’ve been mildly dehydrated I didn’t notice the early symptoms.  So, I consciously drink three pints of water on a warm day even if I don’t think I need it.

“wouldn’t ‘acclimating’ before a hot trip by drinking less water result in your going into the trip already water poor in terms of body cell storage etc.?”

no, for example, if I have a hot trip starting Saturday, and I can get a couple hours of exercise in hot temps on Thursday, don’t drink any water until after that exercise and I’ll be better acclimatized on Saturday.  I’ll have plenty of water between that exercise and the Saturday trip so not be at all dehydrated then.

At least that’s the theory.

In my mind, acclimatization to heat simply means you’re aware you’re going to suffer some, you’re prepared to sweat, you’re willing to adjust effort accordingly, and you know what the hydration/nutrition needs of your body are.  I’m not sure I view it so much as your physical body adapting to the heat, but instead being aware and adapting habits to the needs of your body.

I live in a hot place and exercise when it’s over 90 or 100 F fairly regularly.  I can’t say that I have some sort of actual physical advantage in the heat because of it- I simply understand what my needs in the heat are, how long I can go with/without water, etc.  Someone from a cool climate might not know and therefor make some big mistakes.

The blunt reality of developing this awareness very much lies in the necessity of being in situations where you did push too far and therefor understand your limits.

Top marathoners drink little why they are running, although many of them have been known to collect the drink bottles along the way and pour them over their heads! It is normal for them to end the marathon quite ‘dehydrated’.

It is better to leave the stomach alone when running, in order that your blood supply focuses on pumping to the muscles. Diverting blood away from your muscles to your stomach is not a way to win races.

Precisely my point above.  So what if it helps win races, that doesn’t mean it’s healthy or useful for multi-day outings.

Drink water, take in some salt now and then, snack occasionally, enjoy the hike, live long.

Scaring people about hyponatremia or excessive fluid intake on a hot day is about the worst advice I can think of.  Heat related illnesses are far more common.  I worked as an EMT.  Our ambulance never once picked up someone ill from from drinking too much while exercising.  Heat related issues were countless, predominately picking people up a mile from the trailhead on summer days or football players collapsed during summer practice.  The first course of action across the board was always pushing fluids.</p>
Elite marathoners are elite marathoners; their efforts are over in < 2:30, they’re acclimated to what they’re doing, and they go in hydrated and re-hydrate promptly upon finishing.  This is very different from the risks faced by the average person hiking at elevation with a load for 6+ hours in the heat.

I’m just going to stay inside until October.

I’m going to wager that the first two weeks of October might still be some of Southern CA’s hottest…

Oof…it’s only beginning….

This is very different from the risks faced by the average [inexperienced] person hiking at elevation with a load for 6+ hours in the heat.
My bold interpolation, but I do have to agree.
We also had to know how handle heat stress and heat stroke in the volunteer bushfire brigade: fire-fighting in the middle of the day. But there we always had the tanker!

Cheers

I deal with heat  all the time at work (construction sites) and I’ve been hiking and backpacking in all weathers for a long time ( As in, grand canyon rim to rim in July – 110 f at the river). Based on my experience – and I will say that 8 hours of carpentry in 100 degree weather is a lot more relevant to backpacking than a marathon run in the heat – I think there are a couple of points that may be of use:

1. Yes, you definitely can acclimatize to heat. But I find it is a slow process – takes weeks in my experience. For me at work it’s seasonal so the adjustment is pretty natural. Keep in mind my experience is on fairly dry climates – California both coastal and mountain. One of the adaptations is sweating more for additional cooling capacity. That one does not apply on humid climates, as more sweat will not cool you there.  I am sure that I sweat more freely after the hot weather has been going on for a while.
2. I am convinced that being outdoors a lot makes me more adaptable weather-wise than if I spent most of my days in a climate controlled environment. This seems to apply to both cold and heat. Being out working in the cold seems to ramp up the metabolism so I stay warmer even at rest than I do if I have been doing a lot of office work. And I’ve noticed this effect on snow camping trips as well – by the end of a week I am running hotter than I was at the start. I see the same efect in my sons with their athletic activities – being out exercising in all weathers seems to make them more able to deal with temeperature variations.
3. Dehydration is a very individual thing. Different folks sweat at different rates, some FAR more than others, and you need to know how YOU respond to heat and how much water YOU need to be drinking to stay well hydrated. Yes, over-hydration can be an issue – though I’ve never been able to achieve that state myself, I think I sweat more than the average. But being dehydrated I think is a lot more likely in most outdoor scenarios, including backpacking, as water sources are not always ready to hand, high mountain air may be dry, and breathing hard means you exhale a considerable amount of moisture as well as sweating it out. I know that I have issues with staying hydrated at work – I tend to not stop often enough to drink, I just keep working – and I will come home with a headache and feel significantly more muscle soreness if I have not been drinking enough. I’ve weighted myself morning and evening and I am sometimes 3 or 4 pounds lighter when I get home from work on a hot day – and I’m only about 150 lbs anyway, so it’s a significant percentage. Someone else my sweat a lot less, and need a considerably lower water intake to be comfortable and safe, but until you know what works for you, don’t assume that someone else’s regimen will suit you.
4. The long term effects of dehydration: kidney stones. Ask me how much fun that is.

Oh – and that grand canyon trip – I drank four gallons of water that day, and pretty much sweated all of that out. Had encrustations of salt all over me.

next question, are you better off with shorts and short sleeves or pants and long sleeves

I used to do shorts because it seems cooler

I switched to pants and long sleeves for bugs and sun.  I thought it would be worse for heat but as it turned out, I think maybe it’s better.

Sweaty clothes are uncomfortable in a way, but maybe they evaporate more so are actually cooler.  Less chance of heat exhaustion.

I’m talking fairly low humidity west coast.