Dehydration does not affect performance - except mentally?

slowsteady

Interesting view coming from some research done in Australia.

http://www.bbc.co.uk/news/magazine-24464774

When you think about it, in the millenia prior to public water systems being developed, human mechanics were built around taking water when and where we found it.

The human body was adapted to tolerate short periods of thirst with minimum loss of efficiency while hunting dinner (the prehistoric marathon:)), otherwise we went hungry:eek:.

ecoli

Just run baby!

Enduro

Good article, and one I tend to agree with from experience. For example, last weekend I did a 6 hour training run without drinking (or eating) anything. I didn't feel that my performance was hindered by that. On the contrary, as you could infer from the article, there is a big psycholgical advantage in knowing that you can do this and not have a dependecy on finding aid stations/ water sources when racing.

average_runner

Enduro wrote: »

Good article, and one I tend to agree with from experience. For example, last weekend I did a 6 hour training run without drinking (or eating) anything. I didn't feel that my performance was hindered by that. On the contrary, as you could infer from the article, there is a big psycholgical advantage in knowing that you can do this and not have a dependecy on finding aid stations/ water sources when racing.

But how much did your drink the week before it?


I can easily do 20 miles without water or food, but mainly because i drink so much throughout the week

drquirky

Enduro wrote: »

For example, last weekend I did a 6 hour training run without drinking (or eating) anything. .

Why?

Duanington

slowsteady wrote: »

Interesting view coming from some research done in Australia.

http://www.bbc.co.uk/news/magazine-24464774

When you think about it, in the millenia prior to public water systems being developed, human mechanics were built around taking water when and where we found it.

The human body was adapted to tolerate short periods of thirst with minimum loss of efficiency while hunting dinner (the prehistoric marathon:)), otherwise we went hungry:eek:.

I've often thought about this one but then " the human body was adapted to tolerate short periods of thirst with minimum loss of efficiency while hunting dinner" is relavent for a time in our history when we had a $hite lifespan and didn't run for the craic

We've evolved as a species and (obviously) live a lot longer - we also run for the craic too so its not an exact comparison.

Personally, I notice a big difference if I'm dehydrated

Enduro

average_runner wrote: »

But how much did your drink the week before it?

I can easily do 20 miles without water or food, but mainly because i drink so much throughout the week

Less than most people I know. I'd guess that I drink a litre or so of actual liquids per day on average. I'd figured out a long time ago that even the old-school advice on how much liquids to consume was meant to include all the the water we consume as part of our food.

I'd do a minimum of 2 - 3 hours running per day on average, if you want to add that factor in.

Enduro

drquirky wrote: »

Why?

Training!

Enduro

Duanington wrote: »

Personally, I notice a big difference if I'm dehydrated

Which is entirely consistant with what the article is saying. What they're inferencing from the Australian research is that there are no physical reasons for you noticing this, that is it is in fact a physchological reaction. The double blind nature of the test is the key to that, which of course would be very hard to replicate in a "try this at home" experiment

Kurt Godel

This is yet more sports-science research that has a misleading publishing title. The conclusion states these data do not support the residing basis behind many of the current hydration guidelines. It certainly doesn't refute those current guidelines. Besides that, its a very small sample size on which to draw significant conclusions from.

Abstract
Background Laboratory studies that support the hydration guidelines of leading governing bodies have shown that dehydration to only −2% of body mass can lead to increase in body temperature and heart rate during exercise, and decrease in performance. These studies, however, have been conducted in relatively windless environments (ie, wind speed <12.9 km/h), without participants being blinded to their hydration status.

Aim To investigate the effect of blinded hydration status on cycling time-trial performance in the heat with ecologically valid facing wind speed conditions.

Methods During three experimental trials, 10 cyclists were dehydrated to −3% body mass by performing 2 h of submaximal exercise (walking and cycling) in the heat, before being reinfused with saline to replace 100%, 33% or 0% of fluid losses, leaving them 0%, −2% or −3% hypohydrated, respectively. Participants then completed a 25 km time trial in the heat (33°C, 40% relative humidity; wind speed 32 km/h) during which their starting hydration status was maintained by infusing saline at a rate equal to their sweat rate. The treatment was participant-blinded and the order was randomised. Completion time, power output, heart rate, rectal temperature and perceptual variables were measured.

Results While rectal temperature was higher beyond 17 km of the time trial in the −3% vs 0% conditions (38.9±0.3°C vs 38.6±0.3°C; p<0.05), no other differences between trials were shown.

Conclusion When well-trained cyclists performed a 25 km cycling time trial under ecologically valid conditions and were blinded to their hydration status, performance, physiological and perceptual variables were not different between trials. These data do not support the residing basis behind many of the current hydration guidelines.

Peterx

always good to see behind the headlines, thanks Kurt Godel.

I would hope a well trained cyclist could do a 25km time trial just after doing a 25km time trial, never mind sitting on their ar$e!

For context that would be like asking a well trained runner to run for 35 minutes without water....

Enduro

Kurt Godel wrote: »

This is yet more sports-science research that has a misleading publishing title. The conclusion states these data do not support the residing basis behind many of the current hydration guidelines. It certainly doesn't refute those current guidelines. Besides that, its a very small sample size on which to draw significant conclusions from.

It's definitely a small sample size, and without knowing the actual details you could see how there would be potential for confounding factors (they're sampling highly trained athletes for a start... all sorts of potential factors there). What would be interesting to know is if there is any good science behind the current guidlines, or are they just "obvious" / received wisdom (I have no idea, by the way... but my sample size of 1 using my own experience very definitely leads me to to think that there is none).

Enduro

Peterx wrote: »

never mind sitting on their ar$e! .

Maybe not... "rectal temperature and perceptual variables were measured." :eek::eek::eek:

Peterx

Enduro wrote: »

Maybe not... "rectal temperature and perceptual variables were measured." :eek::eek::eek:

perception would vary in direct proportion to the proximity of the probe to the seat:)

pconn062

Enduro wrote: »

Less than most people I know. I'd guess that I drink a litre or so of actual liquids per day on average. I'd figured out a long time ago that even the old-school advice on how much liquids to consume was meant to include all the the water we consume as part of our food.

I'd do a minimum of 2 - 3 hours running per day on average, if you want to add that factor in.

Off topic I know, but how the hell do you fit 2-3 hours a day minimum in? Do you run really early in the morning?

plodder

It's true many runners drink too much water. I can never understand the need for carrying water bottles. It must be an awful pain. But, to say that dehydration doesn't affect performance is way too far the other way. Maybe 2% dehydration doesn't affect performance, but I'm sure many runners have experienced more severe dehydration than that (I definitely have), and it definitely affects performance.

PVincent

It's a hard one to comment on, because in reality, sensible athletes rarely leave themselves dehydrated. I certainly agree that it is possible to do 20miles without water, I did long runs for London thro last winter without water, but I was properly hydrated before I ran . It would be an interesting but not a pleasant experiment for someone on Boards to attempt even a 5k whilst dehydrated. Then , and only then could you actually say if it meant a difference. When we run in the heat , and we sweat buckets, is that the heat or a touch of dehydration that is making us suffer? Bit of both maybe!

career_move

I've ridden in horse races when dehydrated and without a doubt it DOES affect you. You feel weak and lethargic and you make stupid decisions.

Duanington

Enduro wrote: »

Which is entirely consistant with what the article is saying. What they're inferencing from the Australian research is that there are no physical reasons for you noticing this, that is it is in fact a physchological reaction. The double blind nature of the test is the key to that, which of course would be very hard to replicate in a "try this at home" experiment

Wait...so its all propaganda?? Damn it.

Seriously though, I get the point - I don't think I was too concerned with dehydration as a child and yet would play football for hours on end without any ill-effects.

BUT then again, if I had been hydratated back then, maybe I would have been a professional footballer by now because I would have been that but better!!?:)

Enduro

pconn062 wrote: »

Off topic I know, but how the hell do you fit 2-3 hours a day minimum in? Do you run really early in the morning?

In the evening after work. I don't watch any TV, so that freed up a lot of time from my pre-athletic life. I'm sure anyone with children would say that the fact that I don't have any makes it easy for me. If I did, I'd probably be looking at getting up early for morning runs (at least that's what I think in my blissful ignorance).

I do most of my training in the hills, which definitely helps from a motivation point of view.

Condo131

Re Article: One word comes to mind: B*##*x!

International Marathon Medical Directors Association (IMMDA) "Revised fluid recommendations for runners and walkers"

Krusty_Clown

Enduro wrote: »

Good article, and one I tend to agree with from experience. For example, last weekend I did a 6 hour training run without drinking (or eating) anything. I didn't feel that my performance was hindered by that. On the contrary, as you could infer from the article, there is a big psycholgical advantage in knowing that you can do this and not have a dependecy on finding aid stations/ water sources when racing.

I'm wondering if we should really be using you as a yard-stick to measure 'average'. You have been running extremely long distances over tough terrain for many years at this stage and the necessary adaptation has likely taken some years to develop. While you can head out for a 5-6 hour run in the mountains without water, I'm pretty sure that I cannot. Yet...

So it may be true to say that 'man does not need water or food for a 5/6 hour run in the mountains', but that's after 'man has adapted to these conditions over a period of many years', otherwise 'man will find himself pretty fooked in the mountains, with no water and no food'.

Enduro

Krusty_Clown wrote: »

I'm wondering if we should really be using you as a yard-stick to measure 'average'. You have been running extremely long distances over tough terrain for many years at this stage and the necessary adaptation has likely taken some years to develop. While you can head out for a 5-6 hour run in the mountains without water, I'm pretty sure that I cannot. Yet...

So it may be true to say that 'man does not need water or food for a 5/6 hour run in the mountains', but that's after 'man has adapted to these conditions over a period of many years', otherwise 'man will find himself pretty fooked in the mountains, with no water and no food'.

I wouldn't consider what I do to be average at all for many reasons, the most obvious of which is that only a small minority of people race the distances I do. Even in the ultra world I'm somewhat unusual in that I compete both on and off road. However I don't think I'm any sort of exceptional freak, far from it.

But then average tells you nothing about what is humanly possible. The average runner's sprinting ability is no indication of how much the 100m world record can be lowered to, for example. In terms of what is humanly possible it the extreme outlyers that tell you a lot more. One outlyer is enough to disprove a "cannot".

Your point about adaptation is entirely correct. Indeed it's exactly the point I usually try to make myself. Adaptation is the body's response to stress. So by stressing ourselves over time, and allowing the body to adapt in reponse, we make ourselves faster/stronger/more resiliant. That's the whole purpose of training runs. I've always thought that running on empty would most likely cause the body to adapt to not needing a constant supply of food. Modern nutrition theory now supports that entirely (switching to fat burn etc). Similarly I always reckoned that something similar would happen with liquid intake. My own experiences, and observational comparisons with other athletes who I race with, lead me to think that this is the case.

So absolutely the average joe athlete would probably run into problems going for a 5 or 6 hour run in the hills without training up towards doing so. But I reckon that most people could get there over period of time (and not necssarily years and years either... less)

Krusty_Clown

Enduro wrote: »

My own experiences, and observational comparisons with other athletes who I race with, lead me to think that this is the case.

That raises an interesting point: Would these other athletes you race with compete in a similar domain? i.e. extreme distances or remote wilderness type scenarios? Perhaps this adaptation makes more sense in this type of scenario, but is less relevant if one's goal is to perform at one's best in a 10k race, or a big city marathon (where water isn't necessary or readily available, respectively).

Let me put it another way: Will taking on water during something like the Mourne ultra marathon adversely affect your performance (beyond the time required to consume the water)?

Enduro

Krusty_Clown wrote: »

That raises an interesting point: Would these other athletes you race with compete in a similar domain? i.e. extreme distances or remote wilderness type scenarios? Perhaps this adaptation makes more sense in this type of scenario, but is less relevant if one's goal is to perform at one's best in a 10k race, or a big city marathon (where water isn't necessary or readily available, respectively).

Let me put it another way: Will taking on water during something like the Mourne ultra marathon adversely affect your performance (beyond the time required to consume the water)?

The ability to run without water over longer distances will have no effect if you're running a distance that doesn't require it. So obviously it's irrelevant for sprinters and middle distance runners etc. It obviously has most benifits in longer distance races in more extreme environments.

But in any event with aid stations then there is a very definite competive advantage in (1) not needing to slow to take liquids and (2) knowing that your competitors probably do need to. The last marathon I raced (causeway coast 3 years ago I think) I incorporated this into a very deliberate racing tactic to try to disrupt the runners with me in the lead group, and it worked very well indeed. If I was racing in a road marathon I'd be trying the same thing (as I reckon I could race a marathon without water these days). In a racing context, any small tactical advantage can potentially be the difference between winning and not winning.

Equally in any event where you need to carry or source your own supplies there is an obvious massive advantage in having to carry considerably less weight around. Those, obviously enough, tend to be more extreme events, such as the UTMB, or even the MWU, for example.