dehydration, think i know the answer

[meic]

I have watched the official and unofficial advice on this subject bounce from post to post over my life time and certain facts stand out which contradict much of it.
It appears to me that there is quite a broad range in the middle which people's bodies are happy with and quite a bit of difference between individuals. At either end of the spectrum we will hit impairment and even danger but there isnt much good agreement on where those limits actually are.

Whilst doing hard physical work in the tropics I would take 6 litres of cordial into the field and drink it all and I would partake freely of the watermelons that I was harvesting. I would then do one pee in the day and I swear it was only a yard long and bright emerald from the vitC! Everything went out of me as sweat.
At first I would take lots of salt on my food at night until I heard of an old (in his 40's ) man who was running around Australia from city to city and at record breaking speeds. He declared that he never put salt on his food or otherwise added extra salt ever. So I too stopped taking salt with no ill effects.

I seem to recall that most people bandy around the figure of 500cc per hour and that is people calling themselves sports people. So it would appear that if you aim for this amount but let your body sway you to take more or less you should be OK.

I do now have a problem with cramps after exercise and I do find that the drinks do work in preventing those cramps (although at a fraction of the recommended doses).

Can you look at your on-ride intake in isolation form your normal lifestyle?
Do most standard people actually have enough surplus sodium in their bodies that it will not be flushed out in a day's ride? Yet super health-minded people are not well stocked in body salt? What is the time span involved?

I am not good at taking on enough water and I will sometimes neglect drinking on a strenuous 200k Audax and I will get a "hangover" with a headache the next day on occasions.

[meic]

I have been reading up on this in my sports nutrition book.

It appears that this problem is a problem only for some people rather than a problem of over-hydration generally. Looking at it the other way, for 87% of even marathon runners the problem is still getting enough water, not too much water.


It appears that I am one of these "salty sweaters" who have to keep aware of this, so if I was to upgrade to running marathons, instead of the more moderate but longer lasting Audax, I would need to consider taking extra electrolytes, before, during and after. Yet I still have to drink at least as much as others.
For most people the big problem is getting not enough water and the book was suggesting much higher figures than 500cc per hour for "strenuous" sports activity.
As an individual you should be aware of your own fluid needs, how much you are sweating on the day.

[Mattie]

Personally I am happy that I can recognise the symptoms of dehydration in myself, and I know what it feels like and how to deal with it. I was just trying to share some of my experience with others.

Others will just have to work it out for themselves.

[meic]

The nutrition book also mentioned the symptoms that you described as being caused by dehydration and of course that interferes with your ability to perform athletically (which is their big concern).
Though if you reach that level of dehydration in an event, you will have already "lost", for less sporty types like myself you can drink more at that stage and not ruin your whole day.

[wearwell]

In very hot weather water requirements for cooling, and other bodily functions, overlap. You lose water by sweating (to cool the body) and respiration. This is then replaced by drinking cold water (or lager for choice) which also cools the body a touch. It's also useful to stick your head under the tap (or in the pond etc), or soak your t shirt before pedaling off.
Getting over heated is not necessarily the same as being de-hydrated. I've had the over heating experience touring in France in mid summer late afternoon. Half an hours rest in the shade made the world feel quite different!

[Jonty]

I find that when cycling I rarely need a pee even if I thought I needed one before starting. The need seems to disappear as I start riding and sweating. It's almost as if my body is reponding to the need to retain fluid in order to sweat. Also my sweat is very salty. I know from playing squash and climbing that I'm a heavy sweater - which can be concealed to a large extent when riding due to the drying effect of air friction - so I have a drink once I feel a bit thirsty and have salt in my porridge and on my egg before cycling, and I put a pinch in my drinking water and on my lunch.
When not cycling I don't put salt on my food.
We're all different.
jonty

[TomTurner]

I find that when cycling I rarely need a pee even if I thought I needed one before starting. The need seems to disappear as I start riding and sweating. It's almost as if my body is reponding to the need to retain fluid in order to sweat.

I have the same experience I have also noticed that my helmet straps develop a white powder on longer rides, I found that this was salt crystalizing from my sweat! Not a small amount either; enough to put on your chips!

But as I said before, the best way to stay well hydrated, cramp free and avoid nasty illness like exhaustion and death, just listen to your body. "If it feels good do it!"

[Michael R]

I find that when cycling I rarely need a pee even if I thought I needed one before starting. The need seems to disappear as I start riding and sweating. It's almost as if my body is reponding to the need to retain fluid in order to sweat.

I have the same experience I have also noticed that my helmet straps develop a white powder on longer rides, I found that this was salt crystalizing from my sweat! Not a small amount either; enough to put on your chips!

But as I said before, the best way to stay well hydrated, cramp free and avoid nasty illness like exhaustion and death, just listen to your body. "If it feels good do it!"

That is simplistic. We may feel good and possibly macho, but we still need the right amount of liquid and food.

I feel good up to 30 or so miles and then start to flag. That's OK for a 30 mile ride as I am back in the house but for 40,50, 60 I am in a mess. Over 30 miles I stop every hour or so regardless and drink and eat

[Deckie]

I think the problem with these isotonic drinks, particularly those you mix your self, is the concentration of salts in them.

The body absorbs water through the gut by osmosis. This, as I am sure you all remember from your school biology lessons, involves the water moving across a semi-permeable membrane (the gut wall) from a low concentration solution to a high concentration solution. If the contents of the gut (i.e. the isotonic drink mix) is a stronger concentration than the body then water will flow into the gut, not out and you will dehydrate.

Water is your best drink, maybe with a bit of squash or something if you don't like drinking straight water. Keep the isotonics for a small drink during a break or after the ride to top you up, or have some salt on your food after.

[niggle]

Today I went out for a 35 mile ride in hot and sunny conditions (well by local standards, bike computer declared it was 31°C at one point but I did get it from Lidl ) It was also quite a hilly ride but I got by on one 750ml bottle of water and felt fine, even stopped for a pee mid way. On getting home just had a large glass of squash with my evening meal, don't seem to need any more to drink at the moment. Before the ride I had only drunk one cup of coffee all day.