I asked this same question recently to a colleague who is an expert in exercise physiology with ~45 years experience, he definitively said "no", this would provide no useful stimulus for adaptations beyond training while well hydrated, and that it would probably be a long-term negative because your recovery would be compromised.

Maybe there would be a psychological advantage but I can't think of a physiological one.

Training in the heat has benefits for racing in the heat but that's sort of a different thing.

Don't know of any value to adapt to anything, but after getting into more long course training, I find I can run 30 k or bike 3-3.5 hours at an easy pace on cool weather without drinking or eating anything. Anything longer and I need to start eating and drinking early in the workout to prevent bonking.

I think the "car analogy" goes both ways, yeah you need fuel and oil to keep it going but there are reserves in tanks too, don't want to go too deep but don't need 200 grams of carbs for every one hour workout.

I actually think this the correct response to the OP's goal, which as far as I can see is to improve performance whilst in a dehydrated state.

Without wishing to delve too deep into the physiology, water is present in different compartments within the body - inside cells, in the extracellular fluid and in the blood plasma. Of these the blood volume is most important to performance in aerobic exercise, and so if we can maintain blood volume and instead lose fluid from the other compartments we can mitigate against a decrease in performance as we become dehydrated. This is basically why elite marathoners can flat pace races despite finishing so dehydrated.

The key adaption to maintain plasma volume is to produce sweat that is more dilute so that less sodium is lost from the blood which then maintains its volume thorugh osmosis. Decreased sodium concnetration in sweat is one of the key acclimations we induce by training in hot enviroments.

Running everywhere in a coat ain't neccessarily the most fun thing in the world though...

Interested in this thread. I don’t know the answer but in your example, that may be what happens the first time you do a dehydrated workout, but the point is adaptation. Does your body improve from that experience and adapt such that it benefits on race day (or when fully hydrated) in a similar way that is would initially suffer from but then adapt better to heat??

I'm not sure we can learn much about human physiology by comparing with cars or planes, but both analogies above are wrong. Water is not fuel (thought it may help move fuel) for humans like gas is for planes and cars.

So the better analogy might be running car with radiator half drained, or the plane maybe with hydraulic fluid drained.

Note, I'm just arguing about analogies -- I'm going to take your advice to heart Dev.

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I think the issue is the synergies between heat adaptation/response and hydration dynamics. We look at heat acclimatization and see its effect on numerous systems and certainly many influencing our abilities to "endure" in heat through adaptation of our sweat efficiency, core temp, bloodshunting, plasma... all of these arguably have a fluid balance component so its presence (hydration) for heat adaptation seems pretty critical ex: we know heat stress - heat stroke symptoms are exacerbated by dehydration. Doubling down on heat and dehydration usually means a trip to the ER, but perhaps there is more to it?

You have stumbled on a yet to be studied (to my knowledge) adaptation from dehydration independent of heat. It is a tough study to pull off as you would want to control for heat and vary hydration state to weed out specific effects. In the name of science it is useful, its value to endurance sport would be a a much bigger question. Maybe it would mimic heat acclimatization to a degree and be another way to approach a "hot race" without turning on the heater or wearing a Parka on the trainer;)

Ex: Have the fan blowing and AC on just make sure you are a few quarts low on fluid and let her rip, but not too low (pink for now).

Maybe some different mechanisms, however, it would need a lot of study to bring it into some practical deployment (if it shows some value of course). Interesting idea at the very least.

Cheers!

No .

This type of workout pacing teaches you what you are capable of so you dont over pace and lose to much too early.

You cant replace as fast as the rate you lose.

Here are thing your body adapts to that improve performance.

Muscle load
Muscle timing
Skill to move easier ( relaxed)

Things that make you faster without adapting.
Body wt.
Mental will and focus.
Proper pacing for your ability.

Adapting to heat is a self regulated system you can not alter with any changes , why some dont do well in kona etc. They heat up alot to move.

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Technique will always last longer then energy production. Improve biomechanics, improve performance.
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That is not true.

Fasting training doesnt teach your body to learn to burn fat. It only allows you to have the speed to burn fats.

Notice how many 5 km and 10 km runners operate soley on glucose for race and have no body fat.

How is that possible? Please explain.

I have under 4 % body fat and live on carbs please explain why I can burn so much fat but the 20% body fat guy cant lose wt with all his fasting workouts.

Not being rude you just are misinformed on how the body uses energy systems it is based on effort not what is available.

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Technique will always last longer then energy production. Improve biomechanics, improve performance.
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Lots of good discussion here!
And yes to reiterate the question. "Is there an adaptation that occurs training dehydrated?"

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I think I read it. ?

I should have said not gas in your car but coolant. Or motor oil.
Gas would be gluscose.

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Technique will always last longer then energy production. Improve biomechanics, improve performance.
http://Www.anthonytoth.ca, triathletetoth@twitter

Here is the only benefit to training dehydrated.

Phycolgical pacing and race prep.

Story .
2010 I did 225 km bike hard in penticton was 40 degrees out. A had I beleive 10 water bottles but even that wasnt enough.

Next day i go do a 44 km run. So slow, I was so bad. Luckily a friend rode by and gave me drink and calories. I finished


Race day felt much easier. And I made a big point to not get behind the eight ball on drinking and nutrition. First sub 9 hr ironman.

Sounds like that training helped but if my buddy never came by at 25 km I may have ended up injured, burnout or walking and not.getting in run training.

If you want to increase.your performance find what you need for x conditions so you can train more with more load and pace.

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Technique will always last longer then energy production. Improve biomechanics, improve performance.
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Perhaps there was some adaptation that occurred before your friend bailed you out at 25km? It is just as plausible as what you believe.

Seriously, you are taking your experience and knowledge and making convicted and unsupported statements. Fast does not always equal right. Your ends to not justify your means. As I stated previously, you have confounded the question with heat (>40 degrees).

BTW, I would take your sub-9 and be wrong all the time;)

Step back from it and let your mind work. It could be nothing (training dehydrated independent of heat), but your definitive stance is not based on any consensus data.

Cheers!

Training dehydrated is the new altitude training. One can gather from the research out there that it would increase plasma volume similar to heat training.

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BoulderCyclingCoach.com

Add heat adaptation to your list.

No adaption on my run. Adaption doesn't happen in one session. Or a single track session would make us all Olympic champs.

I was giving an example of a single session that I learned from that helped me better race hydrated and fuel intake. I never said it was data or proof of x. I said the result made me notice I need more to perform better.

My stance is based on college text books that have studies that show power outputs to hydration and know body winning a race without hydration and fuel. Show me the race result were an athlete said I had no water or fuel and went faster????

Lets not discuss heat totally different topic and so much misinformation.

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Technique will always last longer then energy production. Improve biomechanics, improve performance.
http://Www.anthonytoth.ca, triathletetoth@twitter

not really heat adapting is the same for all and regulated by the brain not decision making.


The other three pointed out there actually improve performance in the heat and make racing in the heat easier as the effort is lowered for the same speed.

They are learned skills that can be learned faster and improve performance.

most heat issues are about pacing the system not to overload user error may occur.

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Technique will always last longer then energy production. Improve biomechanics, improve performance.
http://Www.anthonytoth.ca, triathletetoth@twitter

Aside from family history, dehydration is the primary cause of kidney stones. Having experienced that once, I have ZERO interest in having another kidney stone. I spent two nights in the hospital, and felt like I was being continuously punched in the lower back by Mike Tyson for 5 days before I finally passed it. Whatever small, unproven benefit there might be to training dehydrated is nothing compared to the pleasure of passing a stone, so make your hydration choices wisely.

Energy systems are also time dependent, not effort dependent. The way the body uses energy systems is not as straightforward as you make it seem. Energy systems don't shut off. The percentage of each used to contribute to ATP production will change with intensity AND duration.

Your example of your godly 4% bf vs Mr. 20% is not as simple as you present it.

Heat is a stress to the system, dehydration is a stress to the system, altitude can be a stress to the system, lack of sleep can be a stress to the system. All stresses on the system will have an impact on performance of cognitive or physical capabilities. People can adapt and mitigate that shock to the system.

I'm not saying dehydration is a plausible training variable. I'm saying that you post in a very definitive manner that leaves a lot to be desired. Be careful before you paint other posters with a broad "uninformed" brush. You make some valid points, but you are also woefully simplifying other physiologic processes.

I generally agree on all these points.

I have to add though that training that pushes the limits in times where the body is physiologically blowing up can ‘callous the mind,’ in the words of David Goggins.

I don’t typically train in low resource environments physiologically, but think occasionally it is good to go to that place where you’re hanging on by a thread in your mind and body to know what it feels like - but hopefully only approach this place in a careful manner as storming the body’s limits in dehydration or excess loss of electrolytes can fracture the mind or body.

I typically bring a Camelback on nearly all my runs outside now and would probably race with it as well just because I like the feeling of high performance in a well hydrated environment. I think I have a pretty good idea of what acceptable fluid loss feels like.

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https://www.strava.com/...tes/zachary_mckinney

Also, I have to add that training and replenishing fluids in high fluid loss environments is beneficial - I think it is a way of staying ahead of looming dehydration or loss of electrolytes constantly. Knowing your rate of fluid loss and being in touch with your body and environment is key.

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https://www.strava.com/...tes/zachary_mckinney

I would write stuff but I am busy now that I am back to work and I don't care. go train without drinking good luck with that. just do what you think works.

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Technique will always last longer then energy production. Improve biomechanics, improve performance.
http://Www.anthonytoth.ca, triathletetoth@twitter

https://link.springer.com/...7/s40279-019-01188-5

Summary, it's complicated.

There is one study in there that has mild indication that there is a degree of adaptation from training in a hypohydrated state can occur.

Thanks for not caring. I also never said dehydration was a good option. Good chat.

You are missing the point yet again my friend and introduced yet another confound in your reply...fuel. BTW, you are the one that introduced heat not me. I suggested to try and look at them separately despite the obvious overlap as this was the OP questions.

Clearly, we all understand that dehydration (% definition withstanding) generally leads to performance decline (as does altitude).

What we do not understand if you can adapt to stave off the decline through periodic training and exposure to said state of dehydration (dose the stressor to train the system). It is quite simple.

Can the threshold of performance decline secondary to dehydration be changed by training in a dehydrated state? And to prevent another reply and getting it wrong, let's be sensible about what that would likely mean in terms of exposure to the stress of dehydration and training. No one would suggest doing this everyday at a 10% loss.

Maybe it would be live dehydrated and train bloated;)

Do not get it twisted, I am not endorsing the practice of training dehydrated, but the question itself (at some level) is not a bad one at all, it just needs to be studied more to understand its value.

Cheers!

Akerman, A. P., et al. (2016). "Heat stress and dehydration in adapting for performance: Good, bad, both, or neither?" Temperature (Austin) 3(3): 412-436.
Physiological systems respond acutely to stress to minimize homeostatic disturbance, and typically adapt to chronic stress to enhance tolerance to that or a related stressor. It is legitimate to ask whether dehydration is a valuable stressor in stimulating adaptation per se. While hypoxia has had long-standing interest by athletes and researchers as an ergogenic aid, heat and nutritional stressors have had little interest until the past decade. Heat and dehydration are highly interlinked in their causation and the physiological strain they induce, so their individual roles in adaptation are difficult to delineate. The effectiveness of heat acclimation as an ergogenic aid remains unclear for team sport and endurance athletes despite several recent studies on this topic. Very few studies have examined the potential ergogenic (or ergolytic) adaptations to ecologically-valid dehydration as a stressor in its own right, despite longstanding evidence of relevant fluid-regulatory adaptations from short-term hypohydration. Transient and self-limiting dehydration (e.g., as constrained by thirst), as with most forms of stress, might have a time and a place in physiological or behavioral adaptations independently or by exacerbating other stressors (esp. heat); it cannot be dismissed without the appropriate evidence. The present review did not identify such evidence. Future research should identify how the magnitude and timing of dehydration might augment or interfere with the adaptive processes in behaviorally constrained versus unconstrained humans.

I cant break down everything you posted and reply to everyone as it just spread on here and even though people agree they get tripped up my a term or wording an idea and moving the conversation to a different topic.

You can PM if it is very important.

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Technique will always last longer then energy production. Improve biomechanics, improve performance.
http://Www.anthonytoth.ca, triathletetoth@twitter