View Full Version : Staying Hydrated
ChinMusic
04-06-2009, 14:54
I don't know if it's just me, but I find that I almost have to MAKE myself drink enough while on the trail. I just did a trip to the Big South Fork last week and on one day I noticed that I never touched my drink bottle from the time I broke camp until I set up in the evening. It was NOT by design.
I know I tend to eat less on a short trip (less than a week) but I really tend to drink less too. I know it can't be good for me.
Does anyone else almost have to force themselves to drink?
Dholmblad
04-06-2009, 15:30
get one of the bladders with a hose. you will find yourself drinking atleast twice as much water because you dont have to stop to sip.
droptopbenz
04-06-2009, 15:30
drink or die! your choice!
Most Americans are conditioned from a very young age to drink something other than water. Often, we accustom our tastebuds to drinks that contain sweetners. While we certainly have the ability taste sweetness not all drinks need to be sweet. That may be what you are experiencing. In my mind, nothing quenches my thirst and makes me feel like I'm giving my body what it needs the most than drinking fresh clean clear spring water bubbling from the ground.
ChinMusic
04-06-2009, 16:51
Most Americans are conditioned from a very young age to drink something other than water. Often, we accustom our tastebuds to drinks that contain sweetners. While we certainly have the ability taste sweetness not all drinks need to be sweet. That may be what you are experiencing. In my mind, nothing quenches my thirst and makes me feel like I'm giving my body what it needs the most than drinking fresh clean clear spring water bubbling from the ground.
That makes sense but it wouldn't answer the lack of appetite on a short trip too. I would assume that after a week or so that goes away.
I too like the spring water, either by itself or with a dash of Crystal Light Peach Ice Tea mix.....good stuff.
I was just surprised that I hadn't gotten thirsty during the eight hours on the trail that day. Granted the weather was cool and I had cameled-up before breaking camp. I felt no ill effects but knew it couldn't be good for me.
From what I've read, most Americans are dehydrated to some degree. By the time we sense thirst in our mouths we are even more severely dehydrated. Even if I have to force down water to some extent I will do it if I know I have not been consuming enough. I kinda think of water as oil is to a car. Clean oil, in the right amts., is necessary for the operation of a car just as clean water is necessary to the proper operation of cells, organs, muscles, and joints of the human body. When I get off the trail and take that first sip of chlorinated fluoridated tap water it makes me realize how much I miss the clean water of the trail.
daddytwosticks
04-06-2009, 19:11
All my hikes are short in duration. My appetite goes away while on the trail. I have to eat small snacks/meals throughout the day in order to keep my energy up. Don't know the science behind this. One other point strange as it may be...although I loose my appetite while hiking, I still have terrible cravings for things like big greasy hamburgers! :)
Dances with Mice
04-06-2009, 20:30
Yep, yep, yep. I know exactly what you're talking about.
When I was "leading" (actually I was called an 'Advisor') a Crew of Venturing Scouts - older teen boys - I found out that dehydration would sneak up on them, actually on all of us, so slow that it took way too long for me to recognize it. They started getting tired and cranky, little things would turn into big problems, they wanted to stop way before our destination, would be constantly complaining and they were all around just hard to be around. I was spending too much time fighting little brush fires to recognize the cause of the raging wildfire. They were snapping at each other, I was snapping at them, I was grabbing the map and compass and leading when I should have been following and letting them make decisions that I only evaluated in terms of safety. They weren't having a good time and I wasn't doing my job.
But one day I noticed that once we stopped and got supper and loaded everyone up with drink they were suddenly all full of energy and the exact same boys who were snapping at each other and dragging their feet too tired to take another step an hour or so ago were circled up in the middle of the campsite playing hackysack.
What was that all about?
So one time when everything but the trail started to go downhill I stopped the hike in the middle of nowhere and had them break out their water bottles and drink a quart of water. We weren't moving, we weren't camping we weren't doing any damn thing until everyone drained a quart. Or as much as they could, some of the boys just weren't big enough to hold a quart. But I had them drink until water was coming out their ears. Twenty minutes later, yeah I timed it, all the kids were in a better mood. Instead of being at each others throats they were checking put the map together and ready to hit the trail and finish off the days hike.
So I started enforcing it - half a quart of water per half hour. Everyone could drink that much. One quart of water an hour. It got to be a joke, I have pictures of the boys making faces as they drank from their bottles, sometimes pretending they were on IV's. It was funny but I guess you had to be there. There was lots of stopping to pee but we moved faster and easier; the group mood noticeably improved.
That was some years ago. But now when I'm out on a week hike I self enforce the same regimen - one quart an hour, thirsty or not. I hike longer and I'm not ready to just pitch the tent and crawl into a sleeping bag at the end of the day.
In the last couple of years I've developed a tendency to have gout. It's been cured by a bit of a lifestyle change which includes drinking one gallon of water per day in excess of any other drinks. A quart in the morning, another at lunch, one in the afternoon before I leave work and another at home. That's in addition to coffee or sodas or wine at dinner. I have a desk job, on weekends when I work outside I up the volume even more.
So yeah, in cold weather or rainy days I don't get as thirsty. I have to force it. I watch the time and chug my prescription of water. Sometimes it's a chore that I do just because. But I'm glad I make myself do it at the end of the day. I'm also glad I don't sit around drinking lots of water during supper then have to get up every couple of hours all night to water the bushes.
Excuse me. I'd write more but I have to go pee.
fredmugs
04-15-2009, 17:06
I think this is similar to the Hike Your Own Hike concept. Your body will tell you when it's thirsty and you'll drink. You don't need to force yourself into it unless you're suffering from heat exhaustion or something like that. On average 2 liters of water will last me 10 miles. Sometimes it doesn't last 5 (hot day, hard climbs, etc). In March I did a 26 mile day and had water left over and that includes using 16 ounces to make a dehydrated meal.
As long as I'm sweating and peeing it's all good.
drastic_quench
04-15-2009, 18:51
That sounds like a lot of agua, Mice. I'd be careful not to go overboard - especially with kids.
http://en.wikipedia.org/wiki/Water_intoxication
YoungMoose
04-15-2009, 18:55
for the first few days when i went on a 2week trip i didnt drink anything. but then after that i couldnt get enough water
Mrs Baggins
04-15-2009, 19:08
get one of the bladders with a hose. you will find yourself drinking atleast twice as much water because you dont have to stop to sip.
Yep. Turned out to be the best thing I ever bought. My husband bought one this year.
Duiring the day while hiking I usually drink enough to stay hydrated. Having a Camelback helps.
But I find it difficult to camel-up in the morning before pushing off. I just don't feel like drinking much water or anything else when I'm not particularly thirsty. But I know it's the best thing to do, so I takes my medicine.
I drink alot of tea when I hike, which makes me pee, and if its yellow I know I need to drink more water. I don't usually get dehydrated unless there is alot of direct sun. I don't take alot of little sips of water unless I'm drinking tea, which I make with alot of skim milk. When drinking water I drink at least 250ml at a time and if I can't drink 500ml at once I'm not dehydrated. I don't believe in tubes. Little sips just sit in your stomach until it is full enough to empty. On a mountain bike, maybe, but not hiking.
I've cut back on salt alot also, and make sure it isn't excessive. I don't take any sports drinks anymore but will make sure something in my diet has enough sodium and will bring some extra to add to my oatmeal if I have been sweating extra, but I usually get enough from a little jerky each day. I'm not worried about pottassium as the stuff I eat like oats and legumes and stuff is naturally loaded with it. I do like lemon powder for vitamin C and a switch from tea, and it usually has some sodium in it also, but I think most sports drinks are excessive for hiking and more geared for faster paced running or biking. Hiking is a more natural rate of activity and doesn't really require any freakish methods to stay healthy and hydrated. Walk like an Egyptian...
Ladytrekker
04-16-2009, 14:02
I went on a Colorado River trip last summer, and the guides told us that almost all incidents of illness or people that ruin the trips are from dehydration. The guides really force it down your throat to drink, because by the time you get the headache it is to late and it can sneak up on you. When you are active and your body is burning calories whether you are sweating or not your body has to replenish itself with liquids, it is the most important thing you should do. I find that when hiking I make it a point to drink even if I am not thirsty. And if you are not urinating as you normally do then kick up the liquids that means your body does not have enough water to produce it.
I really don't think it should be forced. It should come naturally. People need to experience some dehydration and then learn to prevent them, but they should never be compelled to drink too much water, especially water loaded with too much salt and sugar. Alot of this is too much people repeating the same crap over and over again. Yeah, don't let yourself get dehydrated, and a little extra water to be safe is good, but don't overdo it. Your body has a pretty big tank so keep it at least half full, but don't keep overfilling it. When you do that your not letting your body give you natural signals, and you also risk overhydration which can be equally serious. Letting yourself get a little dehydrated now and then will not kill you and it will teach you to recognize the symptoms.
Walking and drinking water is as basic as it gets. Don't overcomplicate it.
People would tell you to hyperventilate if they could find a way to sell air.
I always thought by the time you are thirsty it's too late, you are already dehydrated.
I am a renal transplant survivor and as such must stay hydrated or risk problems. My rule of thumb is to"camel up" at the start and then every time I have to take a piss also drink. That way I'm replacing what just left.
Farr Away
04-16-2009, 16:11
I don't really get thirsty when I'm hiking, so I need to consciously make an effort to drink enough water. Having a hydration tube helps.
Not being thirsty isn't specific to hiking for me though. At work, I'll make 2 cups of tea (herbal, green, white) at a time. If it's sitting there, I'll drink it. If it's not, I probably won't even notice. I try to drink 4-6 cups a day. On the weekends, I'll sometimes find that I've had my morning coffee and that's pretty much all I drank all day. (I try not to do that - dehydration headaches.)
I've heard that also, but it doesn't make sense to me. I am often thirsty, but don't consider myself dehydrated unless I'm getting lightheaded. Its easy to confuse with other bad stuff like sun burn, sun stroke, heat stroke, muscle fatigue, glycogen depletion, hypothermia, and dehydration is often mixed with those things and make them worse. It's serious, but I still don't think drinking should be forced. We should remember that we are animals doing what animals do. No need to make it over complicated if bears and dogs and deer don't. I also do think it helps to drink in normal amounts, as in gulps, not sips through a tube. If I am thirsty I can chug back 500ml or more. If I'm not then a gulp is enough to tell me I'm not. If there is other stuff going on like fatigue and direct sun or alot of tough hill climbs and stuff then you have to be extra cautious, but drinking when not thirsty doesn't agree with me, especially when mixed with too much salts and sugars. I'll stop and make tea now and then, at least once during my hike, and that is a really good way to stop and assess what's really going on. The tea is bound to make me piss and if its reasonably clear then that's another indication I've been drinking enough. A runny nose and a mouth that isn't too dry are good signs also. I'll admit it is alot more difficult to properly assess things when its hot and humid, especially when combined with normal fatigue. Still, there is a pretty decent range to work with. I think its better to working within that range somewhere in the middle that to be running on empty or overusing your kidneys all the time.
I think the most important thing is to simply keep enough water on you and handy.
The rest comes with you own experience in different conditions and activity levels.
I think listening to your own body and judgement is still the best advise.
Something else to keep in mind is that Marketing folks WILL do you harm, even if that is not their intention. People need to get out and learn as much as they can from nature and from their own bodies, and get away from all that **** that is killing them.
Ladytrekker
04-16-2009, 16:41
Well when I say force it I meant verbally. And your right you can over drink, the point is people will continually during activities say I am ok not thirsty not hungry and then suddenly bam, sick. Of course your body is your best witness let it guide you but be conscience enough to know that you need to drink more when active especially if it is hot. I work in a city morgue and I see all kind of wierd deaths, so just let me say when your body speaks listen.
I don't know if it's just me, but I find that I almost have to MAKE myself drink enough while on the trail. I just did a trip to the Big South Fork last week and on one day I noticed that I never touched my drink bottle from the time I broke camp until I set up in the evening. It was NOT by design.
I know I tend to eat less on a short trip (less than a week) but I really tend to drink less too. I know it can't be good for me.
Does anyone else almost have to force themselves to drink?Getting back to the original post, yeah I used to be that way also. I never carried water out running or hiking or sailing like everyone else. Now I do. I still don't when running less that 20km, but anything more than a couple of hours I make sure I have it on me. I don't think dehydration is as serious an issue under most normal circumstances as everyone seems to be making it out to be these days. Think back to how much water you carried around as a kid, or how much other people have carried and drank throughout history. How big were the old army canteens? They worked didn't they? How much water to animals drink? I seriously think the more serious matter is that most people today eat and drink way too much salt, and as a result of that they are forced to drink and piss way too much.
Seriously. Cut back on the salt and maybe we won't need to piss so much.
I think my diet hunger is kicking in. I should probably get something to eat and drink.
Does anyone know if urine colour is always an indication of dehydration, if if other stuff can give urine a yellow colour, like drinking tea. I've always figured a little yellow colour is normally but now I here some people saying it ought to be clear. What's up?
Footslogger
04-16-2009, 17:03
Does anyone know if urine colour is always an indication of dehydration, if if other stuff can give urine a yellow colour, like drinking tea. I've always figured a little yellow colour is normally but now I here some people saying it ought to be clear. What's up?
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Depends how close to your last meal you urinate ...and of course, what you ate. Urine following a meal is loaded with waste products and excess metabolites/breakdown products of digestion and is often pretty yellow - so NO ...color of urine is not always a good indication of hydration levels.
A couple hours after a meal, if you are fully hydrated, your urine should be near clear and in large quantities and often.
One method the wife and I adopted during our respective thru-hikes was to take a drink EVERY time we thought about water or drinking. Turns out we think about it pretty regularly but until you develop the habit of drinking at those times it is easy to fall behind ...and once you fall behind it is more difficult to catch up. For that reason alone, a hydration system (whichever you prefer) that is convenient is key in staying ahead of the hydration game.
'Slogger
I did some looking into Sports Drinks and they all seem to have way too much sodium and potassium. I suppose the sugar doesn't really do any harm while hiking if you need the sugars anyway, but the salt in sports drinks seems very excessive. Some lemonaid mixes seem to be a better way to add some flavour and vitamin C without adding too much salt and sugar.
This stuff is pretty good. We've been using it for hot lemonaid on day hikes.
http://brands.kraftfoods.com/countrytime/ct_ingredients_OnTheGo.html
It also comes in a Lite version but the 100% vitamin C might be a misprint.
http://brands.kraftfoods.com/countrytime/ct_ingredients_Lite_10.html
I'm still a but dubious of some of the ingredients for drinking it on a long hike as my primary source of vitamin C, but too much tea or cedar bark probably ain't good for me either.
Anyone one know a good lemon or orange drink without too much salt and sugar and other chemicals for the amount of flavour and vitamin C you would be getting?
Footslogger
04-16-2009, 18:01
Anyone one know a good lemon or orange drink without too much salt and sugar and other chemicals for the amount of flavour and vitamin C you would be getting?
=============================
Have you ever tried a product called "Emergen-C".
http://www.emergenc.com/
I wouldn't hike without it any more. Comes in several flavors, including lemon-lime and orange. My favorite is the cranberry.
'Slogger
skinewmexico
04-16-2009, 18:15
We quit letting our scouts use bladders with hoses. I guess none of them were breast fed as children, they walk along sucking on them the entire time, and run out of water miles before we get to another water supply.
Footslogger
04-16-2009, 18:16
We quit letting our scouts use bladders with hoses. I guess none of them were breast fed as children, they walk along sucking on them the entire time, and run out of water miles before we get to another water supply.
==========================
Sounds like they were staying hydrated though ...just sayin'
'Slogger
==============================
Depends how close to your last meal you urinate ...and of course, what you ate. Urine following a meal is loaded with waste products and excess metabolites/breakdown products of digestion and is often pretty yellow - so NO ...color of urine is not always a good indication of hydration levels.
A couple hours after a meal, if you are fully hydrated, your urine should be near clear and in large quantities and often.
One method the wife and I adopted during our respective thru-hikes was to take a drink EVERY time we thought about water or drinking. Turns out we think about it pretty regularly but until you develop the habit of drinking at those times it is easy to fall behind ...and once you fall behind it is more difficult to catch up. For that reason alone, a hydration system (whichever you prefer) that is convenient is key in staying ahead of the hydration game.
'SloggerThat still doesn't address the issue of how much is enough and how much is too much though does it? On the surface it really only provides advice on how to drink more water whether you need it or not. The presumption is that left to our own natural inclinations we won't drink enough. I have trouble with that.
From what I've read we can lose 2% of our body weight before blood volume is effected. For myself that is about 2 litres. On top of that is the water stored with our glycogen, which only needs replacing when we replace our glycogen. Arguable that could be done continuously, but that is 2000 calories for some people and many would leave most of that replenishing for the end of the day. Plus we can toss some into our stomach as we start out. 0.5 litre maybe without just pissing it away. All in all we have about a 2 litre tank before serious dehydration begins, and how long that lasts varies with conditions and activity level. One some hikes you may not need to drink at all before stopping for lunch. On other hikes you might soon deplete that initial 2 litres and then be drinking 1 litre per hour after that and need some electrolytes also. But my point it it varies. I don't think the rule of drinking when not thirsty is a very good one, especially if its a sports drink.
I think its best to keep the tank at least half full. That gives a full litre to work with. When you think you have sweated a half a litre of water you should start replacing it at the same rate as you are using it up. That could be 0.5 litres every half hour or every two hours. If you quess 0.5 litres every 2 hours and you are actually using 0.5 litres every 30 minutes, which is alot of water at a walking pace, it will still be 3 or 4 hours before your tank is empty and if your not thirsty by then you probably should be. Anyhow, if you are sweating a litre an hour and don't know it thats crazy. More likely it is less than that and it will take all day before you are dehydrated, or perhaps things change in the afternoon and you don't respond quick enough because you think your just tired.
I don't think the rule of drinking when not thirsty is a very good one, especially if its a sports drink. I don't think it is very healthy to have to stop and piss too often while hiking. It is better to develop a better idea of how much water you should actually consume while hiking under different conditions, and rely more on your own good judgement and sense of thirst.
It's not a pissing contest. ;)
Here are some interesting quotes from the article on water intoxication...
http://en.wikipedia.org/wiki/Water_intoxication
Prevention
Water intoxication can be prevented if a person's intake of water is limited to his or her losses, this is easily achieved by only drinking when thirsty. Healthy kidneys are able to excrete approximately 1 liter per hour of fluid however stress (from prolonged physical exertion), as well as disease states, can greatly reduce this amount. Sports drinks are popular among athletes because they provide electrolytes to support extended exercise. However all sports drinks are hypotonic and do not contain enough electrolytes to balance excessive intake. Water intoxication should not be confused with dehydration, a loss of fluids (with decreased, normal, or increased electrolytes). However, drinking to satisfy one's thirst prevents both conditions.
I think its better to working within that range somewhere in the middle that to be running on empty or overusing your kidneys all the time.
Sorry JAK I disagree with you on this one. You can't "overuse your kidneys". They work 24/7 and you'd better hope they never stop.
Blood enters your kidneys through the renal vein and is filtered through small structures called "nephrons" removing toxic wastes and making urine. The blood is then pumped back out the kidney through the renal artery. It happens with every heartbeat.
Being dehydrated can cause renal failure, kidneys have to be "swimmin in water" all the time.
Unless you already have kidney failure and are on dialysis there is no need to worry about limiting your fluid intake.
I'll have to disagree with myself on this one too, having thought about it some more. Best to aim somewhere in the middle, between drinking too much and too little. Then lean somewhat towards which is the less risky, which means drinking a little more. Also lean somewhat away from your personal bias, which ever that is. For myself it is probably drinking to little. I would add to that to take a long view and take recent trends and marketing forces with a grain of salt, but not too much salt. ;)
I think there is a pretty healthy range between too much and too little. I think sports drinks have too much salt and sugar for hiking, but you can always dilute them or make your own. Probably a good idea to drink plain water most of the time, just not all day if its a hard sweaty day and you are drinking more than 4 litres. But for most hiking days plain old water is probably best, but a little flavouring and vitamin C and sugar and moderate amount of salt probably doesn't hurt.
What's your though on Sports drinks? How much sodium per day for hiking?
What's your though on Sports drinks? How much sodium per day for hiking?
I don't care for them.I usually just add a pkg of real lemon crystals when I want some taste to the water.
And I don't pay much attention to adding salts unless I'm perspiring much too much, like jungle hot and dripping wet.
Right on. So we are of the same mind after all. I was just ranting off on a flyer. Cheers.
When I was on dialysis (2 years of torture BTW, you DON"T want to have to do that) I was on a NO SALT diet and had to regulate my water intake, since the kidneys aren't working and salt holds water in your system.
After transplant I was told to use salt in moderation. What that means for me is to not add any extra salt to my meals.
I don't usually add salt either, unless I am dieting and no for sure that I am not getting any, and then I add just a little in my oatmeal now and then. While hiking if I bring some jerky or soup mix or something like that there is usually more than enough sodium in that that I needn't worry about sports drinks. I know I get enough potassium in the oatmeal and other stuff I eat. I am not too worried about potassium/sodium balance, but perhaps I should be. Not sure. Do you need more sodium if there is alot of potassium in your diet? Another reason I avoid sports drinks is because I already get enough potassium.
I think this stuff is pretty good...
We've been having hot lemonaid on our dayhikes lately.
http://brands.kraftfoods.com/countrytime/ct_ingredients_OnTheGo.html
http://brands.kraftfoods.com/countrytime/ct_ingredients_Lite_10.html
The Lemonaid Lite seems to have more vitamin C which is interesting,
but calls for half the water for the same sugar as the pouches which is kinda weird.
I'll have to check out the ReaLemon which is what I thought you mentioned.
Then I came across this article, and see you actually said real lemon crystals.
http://ellsworthmaine.com/site/index.php?option=com_mamblog&Itemid=214&task=show&action=view&id=16667&Itemid=214
I'm not sure I like all the stuff in Country Time either. Not to worry too much but I'm looking for something to use a lot of as a natural source of vitamin C and flavouring agent. Not too worried about sugar and salt as long as its not excessive as I can always add my own.
So what is a good source of real lemon crystrals with vitamin C and not too much crap?
The article above mentions one that might be good...
True Lemon Crystallized Lemon
Ingredients: Citric Acid, Lactose (A Milk Derivative), Lemon Juice, Lemon Oil, Maltodextrin, Ascorbic Acid (Vitamin C).
Here is the True Lemon stuff...
http://www.truelemon.com/
http://www.truelemon.com/weightloss.cfm
Still, it isn't a totally natural source, but perhaps better than most.
The other option might be to pack some real lemons and limes and have 1 a day. They don't add all that much weight, and you can squeeze as you go and then eat what's left at the end of the day. Might also be easier to resupply with real lemons and limes than to try and find a healthy powder. Not sure.
We have alot of Eastern Cedar here which is supposed to be a good source of vitamin C.
You might have to be careful if using it every day though. A few leaves is enough to make tea now and then and the inner bark is supposed to be a emergency food source, and also some sort of medicinal drink. I wouldn't recommend it for people with kidney troubles, or for anyone on a regular basis without some more research.
Yellow Birch inner bark is a really nice and easy source of wintergreen. Doesn't take much. That is a easy and safe way to give some nice freshing flavour to cold water or hot tea. I don't think it provides vitamin C though.
Here is a quick list of vitamins and minerals from herbs:
http://www.naturodoc.com/library/nutrition/herbvit.htm
Vitamin C:
Alfalfa, Burdock, Boneset, Catnip, Cayenne, Chickweed, Dandelion, Garlic, Hawthorn Berry, Horseradish, Kelp, Lobelia, Parsley, Plantain, Pokeweed, Papaya, Raspberry, Rose Hips, Shepherd's purse, Strawberry, Watercress, Yellow Dock
We don't have much of that stuff in the woods around here though. Backyard yeah and around farms but not so much in the woods. Cedar is the traditional source in the woods here, and its a good one, but perhaps not for folks with kidney problems.
I seem to drink less when I'm out in the winter. I guess the reason being I sweat heavily in hot weather and am reminded to sip more often. The hydration bladder in the pack is not only convenient but a steady reminder.
Vitamin C requirement is about 90mg per day.
http://www.nal.usda.gov/fnic/foodcomp/search/
It seems an orange or a lemon or both each day might be the best answer.
An orange has about the same vitamin C as a lemon plus a few more calories.
A lemon has more acidity, so perhaps better for flavour.
Limes pack about 1/3 to 1/2 the vitamin C of lemons.
About 1/4 the weight and 1/2 the vitamin C is in the peel,
so you might want to eat that to save weight, unless its full of pesticides and stuff ???
A fresh orange and/or lemon a day would add about 1/4 to 1/2 a pound, which might be excessive. Just one small orange OR lemon each day, 100g per day, wouldn't be so bad.
Ladytrekker
04-17-2009, 12:37
http://www.backpacking-tips.com/hiking-hydration.html
http://www.backpacking-tips.com/hiking-hydration.html
Dan and Dave should get their asses kicked.
Good article on exercise and fluid replacement with numbers.
Data is for running at various body weights and temperature conditions.
Slowest pace is about 8.5 km/hr, but might be comparable to hill hikng with a pack.
http://www.acsm-msse.org/pt/pt-core/template-journal/msse/media/0207.pdf
I think the best advice the article gives is for people to weigh themselves before and after training sessions, like day hikes for example, in order to get to know their own bodies better.