How much water is needed?

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Re: How much water is needed?

Postby Lophophaps » Sun 12 Feb, 2017 8:10 pm

TamarJ wrote:This is pretty typical water consumption for me on hikes, and according to what I read everywhere, I should be dead.


Finally the new website code is working and we are getting messages from the other side. Tamar J, what is it like?
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Re: How much water is needed?

Postby GPSGuided » Sun 12 Feb, 2017 9:28 pm

What never made sense for me is the conflict b/n 1. The recommendation of 500ml/h hydration during sporting activities. 2. 1-2L of water a day on bush trips. As such, I can only conclude that we are partially dehydrated.
Just move it!
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Re: How much water is needed?

Postby Grose Chick » Mon 13 Feb, 2017 12:16 am

Lophophaps wrote:
Grose Chick wrote:This is pretty typical water consumption for me on hikes, and according to what I read everywhere, I should be dead.


Finally the new website code is working and we are getting messages from the other side. Grose Chick, what is it like?


Omg I'm dying here! :lol: :lol: Or am I already dead? :shock: :lol:
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Re: How much water is needed?

Postby Grose Chick » Mon 13 Feb, 2017 12:19 am

500ml/h? I have noticed my typical consumption is approx 100ml/h. Even in hot weather. Strange.
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Re: How much water is needed?

Postby wayno » Mon 13 Feb, 2017 5:16 am

its an over simplification to say you may not need to to start replacing salt straight away when you are exercising. if you normally consume a lot of salt, you will also excrete more sodium in your sweat and urine to dump any excess, and most westerners consume salt to excess, if your diet while hiking has a reduced salt intake than normal and no salt in the water you drink, your body takes time to adjust to the lower intake of salt and keeps excreting sodium at a high rate, bringing about hyponatremia earlier. the variance of sodium in sweat can vary by two fold from person to person,
i dont have scientific references, but what i'm writing comes from reading articles written by physiologists, Dr Tim Noakes is one source in "The Lore of Running"
rate of sweat varies massively, anything up to a couple of litres per hour depending on the weather conditions and how hard you are exercising to prevent your body overheating. take note of the colour of your urine, if its always dark you need to drink more, if you havent peed for a couple of hours, drink more... if the wewather is hoter than average, or hillier than average , drink more than you normally drink, carry more water if needed.
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Re: How much water is needed?

Postby roysta » Mon 13 Feb, 2017 5:26 am

Grose Chick I hear where you're coming from. My intake, even on a 30 degree day with high humidity is about 250-300ml per hour.
In winter conditions with a max of say 7 degrees it might be 50ml per hour.
Generalisations of 1 litre per hour is just that, generalisation.
We're all different.
The idea is to note what works for you and always be prepared to adapt to changing circumstances.



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Re: How much water is needed?

Postby Grose Chick » Mon 13 Feb, 2017 7:42 am

roysta wrote:The idea is to note what works for you and always be prepared to adapt to changing circumstances.


Adapt. I feel that word is key to survival.
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Re: How much water is needed?

Postby slparker » Mon 13 Feb, 2017 11:51 am

roysta wrote:Grose Chick I hear where you're coming from. My intake, even on a 30 degree day with high humidity is about 250-300ml per hour.
In winter conditions with a max of say 7 degrees it might be 50ml per hour.
Generalisations of 1 litre per hour is just that, generalisation.
We're all different.
The idea is to note what works for you and always be prepared to adapt to changing circumstances.



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i don't think that anyone wrote that you should drink 1 l an hour, just that in hot/humid conditions some people drink up to or over this amount.

water consumption should be in relation to thirst and urine output or, for those who know their bodies well, in relation to their known requirements in hot conditions.

Forcibly drinking water has led to hyponatraemia in endurance athletes which is why a minimum amount is not recommended and why thirst and urine output is generally regarded as the best guide.
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Re: How much water is needed?

Postby wayno » Mon 13 Feb, 2017 12:04 pm

I've read some articles, cant recall how scholarly, if scholarly at all... about preloading with a lot of water in the hours before exercise...
most of what i have read advise against this, you're body won't store excess water, it will flush it out as soon as possible, and with it electrolytes including sodium, starting off the process that may lead to hypomatraema.... you might want to have a cup or two of water as you are about to start out walking if its a hot day, but no more and no earlier.
someone i know was running a marathon,, family and friends advised her to preload with water, which she dutifully did the night before and the morning of the marathon... she got half way through the marathon before she cramped up severely and threw up... she said the cramps were more painful than when she had broken her arm....
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Re: How much water is needed?

Postby slparker » Mon 13 Feb, 2017 2:21 pm

wayno wrote:I've read some articles, cant recall how scholarly, if scholarly at all... about preloading with a lot of water in the hours before exercise...
most of what i have read advise against this, you're body won't store excess water, it will flush it out as soon as possible, and with it electrolytes including sodium, starting off the process that may lead to hypomatraema.... you might want to have a cup or two of water as you are about to start out walking if its a hot day, but no more and no earlier.
someone i know was running a marathon,, family and friends advised her to preload with water, which she dutifully did the night before and the morning of the marathon... she got half way through the marathon before she cramped up severely and threw up... she said the cramps were more painful than when she had broken her arm....


there's nothing wrong with making sure that you are adequately hydrated for the next day by drinking water the night before. if you overhydrate then the kidneys will expel a lot of very dilute urine - so you won't lose all your electrolytes. certainly no more than can be replaced by breakfast the next day. Hyponatraemia occurs when athletes forcibly drink massive amounts of water during endurance exercise. heat cramps are not the same as life-threatening hyponatraemia.

many people get heat cramps and heat exhaustion when they do not replace water and electrolytes at the end of a hot day with another hot day following. it is good advice to 'preload' sufficient water to replace water lost during the day. This should only be enough to bring your urine output back to normal. Clearly eating a normal diet will also replace the sodium and other electrolytes lost during the day.

Water consumption should not be restricted in hot weather.
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Re: How much water is needed?

Postby wayno » Mon 13 Feb, 2017 2:59 pm

she didnt have heat cramps , it wasnt a hot day. she had never had cramps like it before even running on hotter days, it wa the only time seh ever suffered cramps of that severe nature, the fact she was vomitting at teh same time as the cramps when it wasnt hot means it wasnt anyting to do with the heat.
you cant urinate unles you are excreting minerals.... the water follows the minerals like sodium, unless you're on a low sodium diet you will keep excreting sodium when you excrete teh excess water, start exdrcising, sweating and drinking water then comes the risk of hyponatremia, and you have to push out other minerals to push out the extra water..
part of the proble with hyponatremia is that you can no longer excrete enough water anymore because you dont have enough minerals available to excrete the water
Last edited by wayno on Mon 13 Feb, 2017 4:17 pm, edited 1 time in total.
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Re: How much water is needed?

Postby RonK » Mon 13 Feb, 2017 3:17 pm

slparker wrote:there's nothing wrong with making sure that you are adequately hydrated for the next day by drinking water the night before. if you overhydrate then the kidneys will expel a lot of very dilute urine - so you won't lose all your electrolytes. certainly no more than can be replaced by breakfast the next day. Hyponatraemia occurs when athletes forcibly drink massive amounts of water during endurance exercise. heat cramps are not the same as life-threatening hyponatraemia.

Whilst I agree in princple with the concept of prehydration, I can't see any advantage in doing it the night before - your body is going to pass it anyway and you'll be awake all night peeing. But certainly you won't be passing electrolyte.

But having lived most of my life in tropical or sub-tropical humidity, it has long been my practice to pre-hydrate in the morning, drinking a litre of water or more before setting out on strenuous activity. And I find I don't need to drink as much during the activity.
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Re: How much water is needed?

Postby slparker » Mon 13 Feb, 2017 4:29 pm

wayno wrote:she didnt have heat cramps , it wasnt a hot day. she had never had cramps like it before even running on hotter days, it wa the only time seh ever suffered cramps of that severe nature, the fact she was vomitting at teh same time as the cramps when it wasnt hot means it wasnt anyting to do with the heat.
you cant urinate unles you are excreting minerals.... the water follows the minerals like sodium, unless you're on a low sodium diet you will keep excreting sodium when you excrete teh excess water, start exdrcising, sweating and drinking water then comes the risk of hyponatremia, and you have to push out other minerals to push out the extra water..
part of the proble with hyponatremia is that you can no longer excrete enough water anymore because you dont have enough minerals available to excrete the water

You can still produce urine in hyponatraemia. Especially high volume hyponatraemia from excess water ingestion. The kidneys filter the water from the blood and, in the presence of the hormone ADH, reabsorbs water. In the case of high volume hyponatraemia the kidneys can expel the excess water from the kidney filtrate by not absorbing it back into the blood, ie by lowering the production of ADH. It is the hormone aldosterone that exchanges sodium at the kidney to pass water and this is not the only method of ridding the body of water..
You can reproduce this state yourself by drinking beer after a long sweaty run. Even in a background of dehydration if you lower the production of ADH (that's what alcohol does) you will pass dilute urine.

In the case of your friend who knows what the mechanism was, but vomiting causes significant electrolyte and water depletion and is as likely a culprit for cramps as anything else.
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Re: How much water is needed?

Postby wayno » Mon 13 Feb, 2017 4:32 pm

the cramps happened before the vomitting
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Re: How much water is needed?

Postby slparker » Mon 13 Feb, 2017 4:34 pm

RonK wrote:
slparker wrote:there's nothing wrong with making sure that you are adequately hydrated for the next day by drinking water the night before. if you overhydrate then the kidneys will expel a lot of very dilute urine - so you won't lose all your electrolytes. certainly no more than can be replaced by breakfast the next day. Hyponatraemia occurs when athletes forcibly drink massive amounts of water during endurance exercise. heat cramps are not the same as life-threatening hyponatraemia.

Whilst I agree in princple with the concept of prehydration, I can't see any advantage in doing it the night before - your body is going to pass it anyway and you'll be awake all night peeing. But certainly you won't be passing electrolyte.

But having lived most of my life in tropical or sub-tropical humidity, it has long been my practice to pre-hydrate in the morning, drinking a litre of water or more before setting out on strenuous activity. And I find I don't need to drink as much during the activity.


Possibly, that's what the army protocol was for extended exercise in hot and humid weather. I did not advocate preloading to the point of excess dilute urine production, more correcting the day's deficit of water and electrolyte loss. No point going to bed and waking up in a state of dehydration.
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Re: How much water is needed?

Postby slparker » Mon 13 Feb, 2017 4:55 pm

wayno wrote:the cramps happened before the vomitting

Perhaps she had a virus, perhaps she was full and didn't eat enough to replace the electrolytes lost in sweat - you cannot extrapolate general physiological principles on a sample size of one.

My point is that starting and event in good hydration, that is consuming enough water to produce an adequate volume and concentration of urine, is a proven strategy for endurance athletes. If you drink a lot of water you will not significantly deplete electrolytes you will produce a very dilute urine. Even if If you were to lose electrolytes a Vegemite sandwich would replace them. Hyponatraemia is caused by electrolyte loss and water consumption in long endurance exercise in a background of insufficient electrolyte consumption. Having a couple of glasses of water before bed or before exercise does not cause hyponatraemia.
The American college of sports medicine recommends replacing electrolytes in endurance exercise via ingestion of food rather than sports drinks and for bushwalking in hot climates drinking and eating regularly is sufficient to maintain both water volume in the blood and electrolyte levels. Again, monitoring urine output annd concentration and eating regularly works best to maintain both adequate blood water and electrolytes. In very hot weather it may not be possible to consume enough water to replace the losses. As sweat is much more dilute then blood water consumption is more important than electrolyte replacement - although electrolytes do need to be replaced.

There is no requirement to add salt to water or to use sports drinks. The body will absorb water via diffusion into the blood without the presence of salt. Eating a muesli bar or fruit and nuts or a Vegemite sandwich during a long walk will replace the electrolytes, no need for fancy drinks or sports bars. They won't hurt but they are not necessary.
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Re: How much water is needed?

Postby wayno » Mon 13 Feb, 2017 5:26 pm

the vast majority of sodium that is lost in exercise, is lost in the sweat. you cant stop sodium lost in sweat..
you can loose 900mg of sodium in a litre of sweat... , that can result in several grams of lost sodium through sweat, maybe even ten to twenty grams of sodium could be lost in sweat in a day..
you may ingest several litres of water to stay hydrated, if you're not eating several grams of salt in your food while you exercise and not putting sodium in your water then you stand to greatly dilute the sodium in your body and may end up hyponatremic...
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Re: How much water is needed?

Postby skibug » Fri 17 Feb, 2017 1:28 pm

Grose Chick wrote:

"I recently walked from Burra Korain in the Grose valley to acacia flats. It took about eight hours ..."

That would be a fairly leisurely walk, or punctuated with long breaks - most people would do this (all downhill) walk in 4 hours or so. Sweating rates will be affected not just by ambient temperature and humidity, but also by muscle work rates - exercise itself greatly increases muscle temperature, which in turn must be regulated by the body (ie sweating). So in hot conditions it is definitely better (in terms of reducing water loss) to walk slowly, avoid climbs and carry less pack weight. There are also many studies (esp military studies of soldiers) that have found that the body can cope with relatively large decreases in hydration levels (I think up to about 10% of BW), which, if followed by rehydration and rest, result in no long term measurable damaging effects. I'll often return from a hot 2 dayer 3 or 4 kilos less than the start, and gradually reabsorb that water over the next day, with only a mild sense of fatigue and thirst.

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Re: How much water is needed?

Postby Grose Chick » Fri 17 Feb, 2017 4:10 pm

Interesting. Yes, I am no fitness junky. I amble along enjoying the scenery. I stop and watch animals or hug trees or whatever pleases me at the time. My pace is definitely suited to my comfort levels, or perhaps just above. Added to that I had never been there before, and for the first two hours that track was vague at best. Then there was the obligatory stop on a rock in the middle off a creek to remove all the leeches from my shoes and socks that had managed to escape my attention. I was so entranced by so many things along the way. I also lost the track around Pierces pass junction, so that was a good time to sit down and have some food and a rest before searching for it again. You kinda get the idea. Pack weight for me is minimal. By necessity. All I had in it was a foil bivvy, a sleeping bag liner, am ultralight inflatable mattress and my jumper. Everything else was in my waist belt, where it was no strain on me. So yes, all those things that you mention would apply to me. Thinking about it, if I had pushed myself harder, I would have most definitely needed a lot more water. And probably a helicopter evacuation. :D With no PLB or phone reception, I was kinda hoping to avoid that scenario. :)
Thank you for sharing your thoughts. My water consumption would make a lot more sense now.
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Re: How much water is needed?

Postby Grose Chick » Fri 17 Feb, 2017 4:14 pm

Pack also contained tarp shelter. 350 grams I think it weighs. All up, well under 2kg.
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Re: How much water is needed?

Postby north-north-west » Sat 18 Feb, 2017 12:36 pm

Especially with coffee being a diuretic, that's amazing, TamarJ. There's a very wide range and you're obviously at one end of the spectrum
Must make life and walking a lot easier.
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Re: How much water is needed?

Postby Grose Chick » Sat 18 Feb, 2017 12:44 pm

I guess so mate. I recall as a child my parents being concerned about the amount (or lack) of water I drank. Just fortunate I guess.
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