Hydration, sweat response and temperature

[jbeegoode]

We got to writing about this topic and I began to think it important enough to warrant its own thread.
I found this: https://www.theglobeandmail.com/life/health-and-fitness/fitness/a-hot-drink-cools-you-faster-than-a-cold-one-myth-or-reality/article4474567/

There is some science in there. It does mention how sweat response is increased by cold liquid intake. Sweat response gets cooped up in clothing. I think what it doesn't address directly, but may be true by the given evidence, is that the body cools better naked. Clothing creates an inefficiency.

Air on a naked body just feels better, but it has been suggested here, that it also provides a difficulty ascertaining whether one is hydrated enough, because the moister drys and disappears so quickly nude. This may be a dry heat thing. I suggest that this may be true, but the best way to be sure is to be aware and know ones body and so practice, by being naked out there often as a norm. When a norm is transgressed, things are more easily noticeable.

Anyone care to add to this? Hot drinks on a warm day? Hot on a hot day. Hot clothed. There seems to be quite a variation and the science is arguing with each other.

With the summer temps dangerously high where I live and in the more swampy areas, this is good information. I'd also like to have evidence that what common sense tells me to be mostly true, that a nude body is more efficient and safe than clothing.

We drenched our shirts with water the other day in extreme dry heat and it cooled until it dried. A wet rag around the neck or head seems to cool, or does it actually cool?

There we go, I hope that we run with this curiosity.
Jbee

[jbeegoode]

A wet cloth at the neck, feet in a cool pool, etc.

http://lifehacker.com/5571072/know-your-bodys-cooling-spots

When hot, there is nothing so satisfying and quick than a breeze all over a naked body, or a patch of shade nude, or a passing cloud to shield, for a while, away from the direct heat. To take clothing off and experience these on a hot day's hike is to transform and be renewed.
Jbee

[eyesup]

The whole sweat/water needed for cooling mechanism is kinda complicated, obviously.

Out here that process can get short circuited because of the low humidity. Water needs heat to evaporate. When it’s on your skin your body expends heat to do that. It also is dependant on the relative humidity. In high humidity it takes more heat transferred to the water to get it into the atmosphere. You get better cooling but takes longer.

In a low humidity environment you lose less heat as the water moves quicker to the air. In a dry and hot environment you get less cooling as the ambient temperature increases the evaporation rate so your body contributes less heat to the process. That’s probably why there is more heat stress and heat stroke out here because people don’t notice that they are sweating just as much, if not more than, wherever they are from.

You retain heat longer and the sun is pumping more into you. It becomes a deadly cycle above certain temps.

Duane

[nuduke]

See my comment on the cooling effect of hot tea in the Everyday Occurrences thread. 
This is my understanding of a wet cloth:  A wet cloth especially a wet towel provides a large area that can be contoured to the skin and the wicking effect of the cloth fibres promotes rapid evaporation.  Evaporation is an endothermic process and requires the input of heat to the liquid which is drawn from the surroundings, some from the skin so that creates active cooling.  A towel does it better because towelling is meant to wick up the water (and does).  For a fever, a damp flannel on the forehead is comforting because it does cool the brow. 


When sweat cannot escape, say in high humidity you feel hot and sweaty.  This is why naturism is so comfortable:  The sweat can easily and quickly evaporate, keeping you cool and comfortable.


John


PS I think I've just repeated what Duane just wrote!  Didn't read it carefully enough, sorry!

[ric]

when your naked youve also got airflow over the skin , clothing holds a static layer of air which acts to stop heat transfer , in the same way a wet suit holds a static layer of water.   

of course this only benefits cooling when the air temp is lower than skin temp....body temp is about 37c ... its rare that  uk air temp exceeds that.

[nudewalker]

On my first experience in the steel industry as a young man I was shocked to see the old timers drinking coffee on a hot day between working around molten iron. Their reasoning was much the same, raise the core temperature to cope with the heat. Also water was frowned on as it may cause cramps; which was the thinking of the day. In fact, our school coaches frowned on too much water intake for the same reason not understanding that the cramps were from lack of water. Gatoraide was a God send to my college soccer team!

In this area humidity is more the culprit than heat itself. We have very few days near 90F (35C?) but the temperature combined with the humidity translates to a feels like temperature which I use to gauge my activity. If the feels like begins to near body temperature then the sweat mechanism is compromised because of evaporation, clothed or naked, but clothed makes it harder to cool down.

[jbeegoode]

Coffee is caffiend and a stimulate, and swells blood vessels and thins blood. I think maybe that this stimulates the sweat response cooling. Anybody have anything on that? The caffiend also keeps the workers working harder and longer, or is more fun.
Jbee

[Greenbare Woods]

My conclusion is that some people prefer hot coffee or tea, while others prefer cold soda or water.  People think of reasons to justify their choice.  I'm not convinced by any of the arguments except that cold is colder than hot.

[jbeegoode]

There was mentioned in what I have read so far of frequent controversy among the "science" studies. Cold is colder than hot, isn't contentious.
There seems to be many variables.
Jbee

[eyesup]

PS I think I've just repeated what Duane just wrote!

Most of us remember better if you repeat it. No harm.

Duane

[eyesup]

My conclusion is that some people prefer hot coffee or tea, while others prefer cold soda or water.  People think of reasons to justify their choice.  I'm not convinced by any of the arguments except that cold is colder than hot.

If I want to warm up in the cold, I drink hot chocolate. Brewed tea or coffee will warm you up initially but then cool you off. That’s ok if it’s not too cold. If I’m cold I light a fire. Also I don’t need the jolt in the evening. Coffee isn’t much of an issue for me, but tea will keep me up.

Duane

[eyesup]

Bob - I'm not convinced by any of the arguments except that cold is colder than hot.
Jbee - Cold is colder than hot, isn't contentious. There seems to be many variables.

Well, after I was banned from the Contrarian Society for having joined, I can say with some authority that there is always two sides to every story. Except for when there are more. Or less.

Duane

[JOhnGw]

Bob - I'm not convinced by any of the arguments except that cold is colder than hot.
Jbee - Cold is colder than hot, isn't contentious. There seems to be many variables.

Well, after I was banned from the Contrarian Society for having joined, I can say with some authority that there is always two sides to every story. Except for when there are more. Or less.

Duane

Or as Groucho Marx put it: "I wouldn't join any club that would have me as a member."

[eyesup]

That is the central tenet of being a contrarian!

Duane

[nuduke]

Steel and forge workers in Britain were well known in times past to drink prodigious quantities of ale (i.e. BEER) during and after work to replace the fluids lost in the fierce temperatures and great effort expended.


John