How much water should we be drinking?

DrParasite

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Question for those in the know (especially those exercise fanatics):

How much water should a person be drinking a day? and more importantly, how much water should be drank before a period of extreme exertion?

A few years ago, a fire captain / department fitness guru told me that if you are drinking water the day of your agility test, you are a few days late. You need to be hydrating several days prior to the test.

At a conference, I heard that when the USAR teams, as well as firefighter strike teams and task forces went down to the gulf and florida, they were showing signs of dehydration, because they were not used to hydrating before their shift, as opposed to local guys who know they need to drink days before they come to work to stay hydrated.

Knowing a little bit about the renal system, I know the body takes in water through the intestines, uses it, and if it doesn't need it, it just dumps it into the ureter to be peed out. It can also reabsorb it through the glomerulus if it finds it needs more. But it's been a while since I reviewed my A&P, esp at this level.

So back to my original question, if I have a shift today at the fire house, and it's expected to be 87 degrees, and we are expecting a physically demanding evening, how much water should I be drinking, can i do it all today or should I have done it for the last 3 days, and if the last 3 days are more important, please explain why, as well as why you can't catch up today?
 

RocketMedic

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Gotta pre-hydrate. Most people are mildly dehydrated all the time, sugary drinks don’t help.
 

Gurby

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I am not an expert, and have been wrong many times before, but I don't think pre-hydrating is a thing (beyond making sure you aren't dehydrated to start).

In fact, drinking a lot of water beforehand is likely to INCREASE your chances of having fluid balance problems, because you lose some sodium along with the urine no matter how well your kidneys are working. Like if you're drinking and peeing, drinking and peeing... you are depleting your body's sodium stores and setting yourself up for trouble later on. I think this article does a pretty good job of explaining: https://www.trainingpeaks.com/blog/how-to-properly-hydrate-before-race-day/

It's very important to pay attention to your electrolytes. If you're sweating a lot, you need to be replacing salt+water. Water alone won't cut it. Gatorade is a step up from water, but still is mostly just sugar. Depending on what your activity is like, maybe water is fine, maybe gatorade is fine, but often you'd ideally be using an oral rehydration solution (like Pedialyte). I've become a big fan of this stuff: https://www.amazon.com/Liquid-I-V-Multiplier-Electrolyte-Supplement/dp/B01IT9NLHW/ref=cm_cr_arp_d_product_top?ie=UTF8&th=1

You can also make your own oral rehydration solution. The WHO has specific guidelines for a whole bunch of electrolytes that should be present, but the most important are sugar and salt. This website recommends 6 tsp sugar, 1/2 tsp salt, in 1L water: https://rehydrate.org/solutions/homemade.htm

So back to my original question, if I have a shift today at the fire house, and it's expected to be 87 degrees, and we are expecting a physically demanding evening, how much water should I be drinking, can i do it all today or should I have done it for the last 3 days, and if the last 3 days are more important, please explain why, as well as why you can't catch up today?
There's no set amount that you "should" be drinking, it depends on your activity level and ins/outs! Drinking too much can be bad, just like drinking too little can be bad. I don't see why you can't catch up today - consume something salty (instant ramen, etc), drink some water but not too much... should be fine....
 

Remi

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Your body does a good job of maintaining fluid & electrolyte balance and won’t hold on to any excess water for long. You can’t really “water load” the same way you’d load up on carbs before a marathon. Extra water means a lower sodium concentration, which your kidneys will correct promptly.
 

Jim37F

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I know that if I've been drinking water the day before, I feel better the next day.

Conversely if I wasnt drinking a lot of water on my days off and try to rehydrate at work, I feel like I can be drinking water all throughout the day but still feel the same thirst in the back of my throat, and def will feel dehydrated when we start getting busy.
 

gotbeerz001

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On a serious note:
Once we start getting into the hot time of year, I’ll drink an extra bottle of water and Gatorade in the late morning. That seems to keep me about right when we break afternoon fires.
 

Rano Pano

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I personally didn't realize how dehydrated I normally was until I made a effort to drink about a gallon a day. The first three days were a struggle to complete, but by the fourth I felt the benefits. My recovery after workouts GREATLY decreased. I no longer felt sore for three days, but a mild sore for about one. My taste became more sensitive to salts, and sugars. I was able to take in 1 to 1.5 gallons a day, and it wasn't a struggle..... I wasn't peeing every 20 minutes either.
Now for hyponatremia, let me state I have no medical conditions, and I don't have a diet that would be considered low sodium.
I don't think a gallon is the answer to everyone. I just wanted to share because I was going through my day to day very dehydrated and assumed it was normal until I made this change.
 

johnrsemt

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I work at a military base: soldiers who drink 1-1.5 liters per hour of water and Gatorade from wakeup to bedtime year round (it gets over 100 good part of the summer) seem to never get dehydrated. Also what the military is pushing.

Back in 2004 when I was in Indiana I was part of EMS group (in charge) that went with Boy Scout group, 350 Scouts and leaders on a 52 mile backpack trip in southern Indiana in July. We had a Medical Resident that was with us doing a couple of research projects (and sutures): and signing off on whatever I needed to do to patients, lol.
1/2 of the backpackers drank (what they wanted {Water, Gatorade, etc no sugar drinks or Soda}) approx. 2 quarts a hour; during hiking, 1/2 quart with breakfast, and lunch; and 1 quart with dinner.
1/2 of the group drank half a gallon before leaving in the morning, enough during morning hiking to keep mouth wet about 1/2 gallon during lunch, enough to keep mouth wet during afternoon hiking, and about a quart with dinner.
At a couple of rough hiking spots we did have someone show up with a Snowcone machine with sugar snowcone flavors, so everyone cheated a little.
No real differences between groups, except how much weight they had to carry: and how many times that had to go to the bathroom.
Doctor wrote a nice paper about that one.
 

Remi

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I also feel better in general when I make a point to drink more water. It may be true that many of us are often in a state of somewhat sub-optimal hydration, owing to our high sodium / high carb diets and frequent consumption of mild diuretics. Still, we are talking a small difference, physiologically speaking. As long as your kidneys (and hypothalamus and pituitary) are working and you are able to freely consume water and are not losing an extraordinary amount due to heat or exertions, your water balance is kept in a pretty narrow range.

There probably also is something to the idea that optimal hydration takes place over hours. When you drink water, it has to pass through all sorts of gradient-driven barriers in order to reach equilibrium between the serum, cells, and interstitium. That takes time and probably multiple separate "doses" of water above what your body is actually requiring at the time.

So I doubt it is necessary to start hydrating a day or two before you need to be optimized, because again, your body can't store "extra" water the way it can certain other nutrients. I'd guesstimate we're talking about a handful of hours of frequent water consumption in order to move yourself from the bottom of the normal range to the top.
 

johnrsemt

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I do think it is a good idea to start drinking a lot a couple of days early to get your body used to it. I have found that I don't pee as often when I am hiking heavy when I start a couple days early; than I do if I just drink a lot more the day I hike. odd, but for me true
 
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