Should I pee or hold it to stay warm?

[sophiecentaur]

That's not a scientific view, that's political view

I couldn't disagree with you - particularly if there were some really hard facts to the contrary.
That 40% figure is not associated with any particular conditions and, of course, it basically advises people,in an overstated way, to wear head covering. If I were to try to sleep out of doors in a proper five season sleeping bag with my head uncovered, it wouldn't surprise me if my head was losing the 40%. I have been in milder conditions than that and my head actually hurt with the cold.
But this isn't Physics and I don't think it can be made into Physics.

 

[DaveC426913]

... this isn't Physics and I don't think it can be made into Physics.

Except that's what it is sold as - what with quoting studies and providing percentage of heat loss.

Those are verifiable - and, notably, falsifiable - claims.
i.e. to state it as fact that "studies have shown 40% etc. etc." is actually a lie.

 

[sophiecentaur]

is actually a lie.

I think you are taking this too seriously for a bit of idle chat.
The 'studies' have not been cited but that doesn't mean they don't exist so calling the statement a lie is over the top, I think. Incorrect doesn't mean a lie. The Science may be bad and the evidence may be dodgy so far but I reckon I could arrange an experiment in which the 40% figure would apply. Insulation fabric can be pretty damn good and the ratio of surface areas of body and head is not great. A 'study' along those lines would produce quotable results which would not involve a 'lie'. Bad Physics and with possible H and S risks but on the right side of safe information.
Isn't this along the same lines as recommended maximum salt and alcohol intake figures and a whole lot of other medic - driven rules? Erring on the safe side is forgivable - much more forgivable than telling people that smoking is harmless. etc. etc.

 

[Laroxe]

Hmm.. I've never really thought about this one but as I read through the answers I thought there was some strange responses. The physics of the rate of heat lost from urine is all really irrelevant when you consider how the temperature is controlled carefully in the body, it is essentially irrelevant to our thermoregulation. Very cold conditions cause vasoconstriction this changes various psychological parameters which our body compensates for by increasing diuresis. So give it time and no choice will be needed. Someone mentioned that opening your pants will effect insulation but even this will depend on the amount of flesh exposed and anyone who claims this is significant in their case clearly isn't worth listening to.:)

The stuff about heat loss from the head is also interesting, its true that someone just in bathing trunks only looses around 10% of their heat through their head but again someone commented on the value of this information in the average survival situation. In a well insulated person the head is often the least well protected and it does have a very rich blood supply it does seem that following heat loss from the head the core body temperature drops more quickly than would be expected presumably because of the blood flow. It also seems that if only the head is exposed to the cold this doesn't activate shivering.
Its hard to identify a single factor that has the most important impact on the risk of hypothermia but if you have a pee and manage to pee all over yourself, being wet must be among the top contenders.

 

[Rive]

Someone mentioned that opening your pants will effect insulation but even this will depend on the amount of flesh exposed and anyone who claims this is significant in their case clearly isn't worth listening to.:)

It's just you likely not had a good all day hike in weather below -20°C, with both trousers and under trousers, paired with a long, thick coat, sweater and stuff.
Takes its time both to loosen all that up and to warm up afterward... And you will think twice next time to hold it or not

 

[DaveC426913]

I think you are taking this too seriously for a bit of idle chat.

I think the reason it's been brought here, to PF, and put in the Bio/Med forum is to separate fact from myth. This wasn't posted in GD.

The 'studies' have not been cited but that doesn't mean they don't exist so calling the statement a lie is over the top, I think.

The studies are cited, lending a false air of authority to the myth that makes it look like it's fact.

Incorrect doesn't mean a lie.

I am not deliberately blowing this out of proportion just for drama's sake. I didn't start out using the word 'lie' until I started to see internet urban legend being defended - and here on PF no less.

This is exactly the opposite of what PF stands for.

The Science may be bad and the evidence may be dodgy so far but I reckon I could arrange an experiment in which the 40% figure would apply. Insulation fabric can be pretty damn good and the ratio of surface areas of body and head is not great. A 'study' along those lines would produce quotable results which would not involve a 'lie'. Bad Physics and with possible H and S risks but on the right side of safe information.
Isn't this along the same lines as recommended maximum salt and alcohol intake figures and a whole lot of other medic - driven rules? Erring on the safe side is forgivable - much more forgivable than telling people that smoking is harmless. etc. etc.

I'm not sure why you're defending such methods. PF is supposed to be a refuge of rationality and fact over emotion and myth.

 

[Rive]

I'm not sure why you're defending such methods.

Your lack of understanding about what 'practical approach' is starting to be rather disturbing.

Taken the study you prefer to call 'fact' as a starting point it takes a lot of completely unnecessary, hazy and dubious calculations over unclear data (clothing and temperature details and such) to get back to the usable 'around 40%'. It would be very refreshing to see you attempt to follow through with all that before so easily calling a direct attempt to provide an useful result a 'lie'.

 

[Mark44]

One way of looking at it, is when you pee, you increase the surface area of your "body (+ pee)" and therefore increase the rate of heat loss.

This makes no sense. Your volume is decreasing, so there will be a (marginal) decrease in surface area.

 

[Mark44]

That's not a scientific view, that's political view

How is that a political view?

to state it as fact that "studies have shown 40% etc. etc." is actually a lie.

I think you are taking this too seriously for a bit of idle chat.

I agree.

The 'studies' have not been cited but that doesn't mean they don't exist so calling the statement a lie is over the top, I think. Incorrect doesn't mean a lie.

I agree with this, as well.
It could be that the 40% figure overstates the amount of heat loss when the head is uncovered, but I doubt that the figure is off by as much as a factor of 2.

Newton's Law of Cooling states that the rate of change of cooling, per unit of time, is proportional to the difference between the object's temperature and that of the ambient environment. Even though the head's surface area is relatively small in comparison to the total surface area of the body, the difference in temperatures between the head and environment vs. those of the rest of the insulated body and environment are much greater. This means that the head will be losing heat at a greater rate per unit area than will the rest of the body.

In any case, all of this discussion of how much heat you lose by not wearing a hat is off-topic.

 

[jedishrfu]

I think you are taking this too seriously for a bit of idle chat.
The 'studies' have not been cited but that doesn't mean they don't exist so calling the statement a lie is over the top, I think. Incorrect doesn't mean a lie. The Science may be bad and the evidence may be dodgy so far but I reckon I could arrange an experiment in which the 40% figure would apply. Insulation fabric can be pretty damn good and the ratio of surface areas of body and head is not great. A 'study' along those lines would produce quotable results which would not involve a 'lie'. Bad Physics and with possible H and S risks but on the right side of safe information.
Isn't this along the same lines as recommended maximum salt and alcohol intake figures and a whole lot of other medic - driven rules? Erring on the safe side is forgivable - much more forgivable than telling people that smoking is harmless. etc. etc.

From LiveScience they debunk the myth of 40% heat loss, A more recent experiment in 2006 showed it to be 7-10% in the British Medical Journal:

https://www.livescience.com/34411-body-heat-loss-head.html
https://www.bmj.com/rapid-response/2011/11/02/head-cover-cold

 

[DaveC426913]

Your lack of understanding about what 'practical approach' is starting to be rather disturbing.

I do not have a lack of understanding of what 'practical approach' is - and yours is not exclusively the argument I am addressing.

This is PF, and this is the Bio/Med Forum, not Farmer's Almanac. To quote you quoting me (post 15):

"This heat-loss myth probably came from experiments in the 1950s..."

How is that a political view?

I don't mean government politics; I mean it is an attempt to manipulate people into doing what you think is best for them by not trusting them to understand the facts for themselves.

Perhaps a better term is superstition.

I think you are taking this too seriously for a bit of idle chat.

I agree.

Again, this is Physics Forums, not Farmer's Almanac. And this is the Bio/Med forum, not GD.

Not exactly the place for myths.

The 'studies' have not been cited but that doesn't mean they don't exist

I agree with this, as well.

Sorry, you misunderstand. My concern is that the studies are being cited - the debunked studies. This lends a false air of authority to what is now a debunked myth.

This means that the head will be losing heat at a greater rate per unit area than will the rest of the body.

So one might think - if one ignores the scientific evidence to the contrary. The later study essentially debunks the myth, despite it being widely-accepted. i.e. the definition of apocryphal.

 

[Rive]

"This heat-loss myth probably came from experiments in the 1950s..."

It should be long clear that this is not a myth and it is not being debunked, despite some journalism claiming so - falsely.

In general, you cannot debunk a special claim with a very loosely connected general one. It is the same story that SR or GR did not (!) 'debunk' Newton, not in the slightest, despite being claimed so so often by some nerds. They have extended the applicable limits of knowledge, but given the same circumstances (and within the applicable range of Newton's) they do, and: they are even expected to provide the very same results, with even mathematical identity.

Ps.: to push it even further, based on physics the first step to even consider the validity of the later heat loss study they would be expected to prove that with the right clothing added and in similar circumstances their results are able to provide the same 'about 40%' results from before.

 

[DaveC426913]

In general, you cannot debunk a special claim with a very loosely connected general one.

What started this, in post 10, was the general claim:

@hutchphd While you are correct and humorous, consider that about 40% of human radiative heat loss is through the head and neck.

Without clarifying context - including important conditionals - the above statement is misleading at best. It's widely held as a fact but, alone, is not useful.

It reads a little too closely like 'don't walk under a ladder because it is bad luck'.

Sure, in some conditions, it might technically be true (getting crowned by a hammer), but superstitions certainly do not belong in the Bio/Med forum of PF, even with the poster's intent for a "practical approach".

 

[Rive]

Some questions still can be basis of useful answers and discussion despite lacking exact details: sometimes, they can get useful answers because they lack some exact details.

Of course it can be an expectation to choke the discussion right at the start with some 'please state your weight, clothing, amount of pee you are planning to dispose in exactly what kind of weather' type of response, but I do not think that is the aim of this forum. It is usually possible to keep being scientific without specifics - or just asking for details and clarification when it is actually not possible.

The original question was not a big start, but still it is quite sad that this topic ends in such zealous style despite bringing up such wide range of relevant extras.

 

[sophiecentaur]

From LiveScience they debunk the myth of 40% heat loss,

The "myth" is not based on specific conditions so it probably needs to be de-bunked. I still hold that there will be conditions where the 40% figure applies.
On the 'political' issue, it is sometimes in peoples' interests to be frightened into good / sensible behaviour and I think this is one example where a bit of overstatement can't do much harm. Death in cold weather is not just an experiment so Physics may not Rule in this case.

 

[Rive]

A more recent experiment in 2006 showed it to be 7-10% in the British Medical Journal:

For me that link opens with the following text on top:

I agree that the simple statement that "40-50% of body heat" is lost
through the head is inaccurate. The true statement is that at – 4 degC half the
heat production of a resting (clad) man may be lost through the head and that
at -15 degC this may rise to 70%. Also in normal circumstances people do not
venture into the cold wearing only swimsuits.
...
To summarise, covering the head in cold weather can produce a marked
effect in subjective comfort and reduction of heat loss. I would hate
to think that this myth-busting exercise, while discouraging them from
venturing out in swimwear, may lead to people going out in very
cold weather (cold, windy and wet) without bothering to protect their
heads.

I believe for those who has access to the article itself this part might be available through the 'response' tab there.

Ps.: check on the author of this response please!

 

[jedishrfu]

We have a mens clothing store here which propagates a similar myth to get men to dress better:

“You only use 8% of your brain…don’t dress accordingly”

which while cute is not quite correct unless you're a student wanting to play video games. :-)

https://en.wikipedia.org/wiki/Ten_percent_of_the_brain_myth
Interestingly, they think the quote came from an experiment on William Sidis, a child prodigy who was raised in an accelerated learning environment.

https://en.wikipedia.org/wiki/William_James_Sidis
The other one they quote is:

“You are the product of 4 billion years of evolution…your clothes are ready”

which is harder to refute since our best estimates say 3.7 billion years ago life started here.

 

[jim mcnamara]

Let's move this to GD.

 

[DaveC426913]

Let's move this to GD.

Wasn't expecting that, but this is a perfectly cromulent resolution to my 'zealous' objections.

GD is a much more appropriate place to discuss opinions of 'what's good for people even if it's not quite factual', in my view.

I hope I didn't seem strident or hysterical. I disagreed with the direction of the thread, expressed it and defended it, but I took pains to be calm, polite and civil (no sarcasm or exclamations, etc.)

Carry on.

 

[Evo]

Everyone is correct, depending on the CIRCUMSTANCES. Please read the entire short article, I can't post it all due to copyright, so will highlight portions.

(45% of body heat dissipates through the head ) This myth likely derives from a misinterpretation of a decades-old US military experiment in which subjects were exposed to extremely cold temperatures while wearing arctic survival suits. However, the suits only covered the subjects from the neck down. Therefore, naturally, the majority of the heat loss occurred by way of the uncovered head.

Since heat loss from anybody region is largely dependent upon surface area, you can see why this belief isn’t logical, because your head comprises only about 10% of your body’s total surface area. Therefore, it’s probably more correct to say that about 10% of body heat is lost through your head—and that’s if your entire body were to be equally insulated.

In reality, the relative amount of heat you lose from your head will vary, depending on a few factors: the clothing you wear, your physical activity level, and the various bodily functions that govern temperature regulation. It’s true that there may be some situations in which one might lose a tremendous amount of relative body heat through the head, such as when it’s the only uncovered part of the body. But in general, the head isn’t a significant area of heat loss—at least not disproportionately more so than any other part of the body.

https://www.onemedical.com/blog/live-well/body-heat
So you are all correct, DEPENDING on the situation. In other words, if it's cold out, keep your head covered!

 

[Dr. Courtney]

Pee. Staying warm is only one aspect of survival. Making good decisions is much more important. The stress induced by not peeing is an enemy of good decision making. The heat loss issue is minor by comparison.

Pee. Take a deep breath. Consider what to do to improve survival odds.

 

[WWGD]

Well, how would one go about testing this more carefully? Fitbit data, then regress it to a 5th degree polynomial? Again, do we have reason to believe peeing is a factor of high importance?

 

[jedishrfu]

I think we about to go off the edge of the world here so I think its time to close this thread.

Thank you all for participating.