Um, no.

I don't know where you live, but I'm in texas. We don't get mongolia cold, but it gets below freezing. I train in the heat in the summer here up to a heat index of ~110*F or so. I monitor my dehydration very carefully. I weigh myself before and after almost every training event, and include fluids consumed to calculate loss-rates. I weigh myself every morning, when I wake up to make sure I start every day fully hydrated.

My peak dehydration rate in the summer is on the order of 7 pounds an hour. Its so much that it isn't possible to absorb fast enough under some training conditions---and I have to replenish several pounds of fluids post-workout.

My peak dehydration rate when the temp is below 40*F, is about 1 pound an hour. That's for a tempo run. Anything lower intensity than that, and the loss-rate is below the noise floor of my scale: essentially zero. There's so much cooling on the bike, that even an hour long threshold workout doesn't always register on the scale. I haven't used a water bottle on the bike since October.

I'm one of those dorks who spends a lot of time on my fat bike.

check out something like this.... https://www.arcticinnovations.com/

but yeah, get the water out of the bite valve too. I (usually) wear my pack under a shell - or a smaller pack closer to the body - to keep the stuff warmer and tuck the tube in when finished.

Maybe one of those thermo flasks, they hold temp (hot and cold) really well for a sustained period. Those flasks are a tad heavy though, but the small model might fight in a jersey pocket.

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Team Zoot 2023

Mostly yes.
I have exercised in some extreme conditions of 40C+ where I thought I was going to die.

But a -26C 2.5hr ski race... no problems.

Yeah, but we're talking running outside in extreme cold no 40F.

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Washed up footy player turned Triathlete.

+30c to -30c sweat rates would be insanely different.

There's no magical source of water loss due to "extreme" cold.

Respiratory water loss goes up as temperature gets colder, but we are talking about mili-liters per hour....like a delta of 30 ml/hour. Not LITERS. So, that's an extra couple of tablespoons. 2/3rds of this effect occurs by the time you reach 32*F. It amounts to roughly 1 1/2 cups over a 24 hour period. Hardly worth writing home about.

The other major factor is how much sweat is being produced based on the appropriateness of the clothing for the temperature. Too much insulation = excess sweat. So, dress appropriately and use layers so that you can shed as you warm up. if you aren't sweating (inner layers aren't getting WET) you aren't loosing water at an appreciable rate. Its really that simple.

5F isn't extreme cold by any stretch. -20F is certainly colder than I would want to go run. But, you do what you gotta do. Wear the right amount of clothing, and sweat rate is controlled and total dehydration is much lower than in the heat.

Well, my experience in Alpine Warfare Training tells me you still need a whole lot of water. That's anecdotal, but you're basically stating he doesn't need to drink. And I disagree. You need water in the cold just like you need it in the heat. We've had heat casualties at (-10F), so there's that.

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Washed up footy player turned Triathlete.

No, I'm saying someone, anyone only needs to drink to match their perspiration rate. if you are sweating (hot or cold), drink. if you are thirsty (hot or cold) drink. If neither, you don't need to. But, there is nothing magic that happens in the cold that makes the water just dissapear. Its sweat, plain and simple.

The easy way to answer the question is, go do a training run in normal training clothes....for an hour or so (don't drink). Weigh before and after---skivvys only. Any difference is water loss.

We aren't talking military operations for 8-12hours or whatever, in full gear. Its a 2 hour run in the cold in whatever clothes are needed to prevent frost-bite.

Today in Minnesota it's negative 34 degrees celsius. I skip camelbak hoses entirely when it's this cold. I either use my xc skiing belt, which is insulated and has a big mouth that screws off, and I fill it with warm water, or I use an insulated handbottle, the nathan speedshot plus. The latter is better for running, the former for cycling and xk skiing. I think the combination of the insulated hand bottle and it being so close to my hand keeps it from freezing completely, and there's a large flow area that doesn't freeze solid if I tip the bottle upside down before drinking.

It's stupid cold today. The mail is not even being delivered. So much for the "nothing stops the mail" saying.

You're not counting the water lost through respiration. More of the body's water supply goes towards heating and hydrating the cold air during inhalation. Or cold-induced diuresis, which blocks the kidney's signals to retain water in the cold (it's why you feel the need to pee when you're in cold water).

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Level II USAT Coach | Level 3 USAC Coach | NASM-CPT
Team Zoot | Tailwind Trailblazer
I can tell you why you're sick, I just can't write you an Rx

Try wearing the Camelback under your jacket or layers and after you drink blow air back into the tube to push all the water in the tube back in to the reservoir.

You people live in some f*cked up places.

It is 60 degrees right now outside and I am in a synthetic down backpacking jacket because its f*cking cold.

The rest of the country is experiencing record colds but here in southern florida - 60 degrees - but to us - that is bloody cold. Like I can't wear flip flops. Its bullsh*t

That was mentioned above, in my previous post:



For Moderate to heavy exercise, water lost to respiration is on the order of 60 ml/hr at room temperature. That goes up to 80 ml/hr at freezing, and only an additional 10 ml (up to 90 ml/hr) at -4 F. So, over a two hour run in the cold, one could expect to expire roughly 1/10th of a liter of H2O. If you want to say that -4F isn't -20, fine double it...that's excessive but ok. Still that's only 2/10th of a liter---just under 1 cup.

For CID...if you're not pee'ing while on the run, its not a concern. If you ARE, then there is an obvious clue that you are loosing water. A full bladder is roughly 1/2 liter, so you'd have to pee a couple times before its significant in dehyddration terms.

My point was NOT that there aren't cold effects. My point was that they are small (when compared to heat induced effects), and that the predominant contributer is, in fact, the SAME contributer as the heat induced effects....ie sweating. The only effect that is "invisible" is respiration loss, and that is not enough to be a concern. Sweating and peeing are obvious. If you are sweating enough to be a problem, your clothes will be WET, not moist or damp, WET. If you pee 5 times on a 2 hour run without drinking...yeah, that might be an issue to manage.

The effects in the cold are NO WORSE than the effects in the heat, and generally are MUCH less, and are easily detectable as either sweating or urination. Same as summer time.

Again, all this is easily manageable by simply tracking body weight before/after a shorter run...and deciding if that weight loss rate is enough of a concern for longer efforts in similar conditions. If so...put a martini in your flask and go for a run. :-)

Shutup and have a frozen, adult beverage.

I ran in Naples yesterday morning and people were out wearing PUFFY COATS AND GLOVES. They looked aghast as I was in shorts and a tank top. You people are cray.

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Level II USAT Coach | Level 3 USAC Coach | NASM-CPT
Team Zoot | Tailwind Trailblazer
I can tell you why you're sick, I just can't write you an Rx

Lol. Puffy coats.

It was 39F here yesterday...still ran in shorts and a tech T. Heck, last month Toby was running WITHOUT A SHIRT in 35F and rain.