# Warm Shower VS Cold Shower

Why do people prefer a warm shower vs a cold shower? I can walk right into a warmer than body temperature shower easily, a cold one not so much. Are we conditioned to like a warmer temperature? Is temperature tolerance/avoidance taught/learned?

I do enjoy a colder shower if I have been doing yardwork outside or have just got in on a hot summer day after exercising.

From my understanding, hot showers opens up your pores while cold showers closes you pores. I know people who prefer cold showers for no other reason than that it is to their liking. Either way you get clean. Though I would think you would have to scrub a little more if the cold shower route is the way to go. However, if you come in from outside, whether exercising or otherwise, it is best to let your body cool down naturally before jumping into the bath.

Your pores don’t open and close; that’s a myth.

I think it’s because relative to our own body temperature, 98 degrees, a hot shower isn’t really that hot, but a cold shower is really cold.

Hot tubs are usually set at 102 degrees and shouldn’t exceed 104. That’s only a +6 degree variance which we remain comfortable.
Go -6 the other way and your at 92 degrees. Still a very comfortable shower.
However, drop down to say 76 degrees or lower, your typical cold tap water, and your talking a variance of -22 degrees. That’s pretty damned cold.

To put some rough numbers to what Hampshire said:

Skin and fat have a thermal conductivity of about 0.2 W/m/K. (For reference, water is about 0.6 W/m/K.) The surface area of a human is about 1.5 m[sup]2[/sup]. Now sit in a bath. Say the separation between the bath water and your body’s 37-degree-C core is about 1 cm. Then,

2 C[sup]o[/sup] difference ==> (0.2 W/m/K)(2 K)(1.5 m[sup]2[/sup])/(0.01 m) = 60 W
10 C[sup]o[/sup] difference ==> 5 times higher than above = 300 W

Under normal conditions, a human outputs about 90 W of heat. So, a 35 degree C bath feels refreshingly cool (helping you get rid of 60 W out of the 90 W you have to get rid of). A 27 degree C bath, though, is sucking out your very soul.

A hot bath at 39 [sup]o[/sup]C (or 102 [sup]o[/sup]F) is a little different in that you need to absorb 60 W of heat. That’s not too bad, though, adding as much internal heat as you would by, say, jogging.

So you estimate the soul at 300W?

Incidentally 27 degrees is just right for a swimming pool, where you will be moving around a bit and generating your own soul-replacing heat. But it’s always damn cold for the first 2 seconds after you jump in.

Thanks for the replies. After reading them it makes alot more sense.

So wait, are you saying that if I take showers at 16C I will need to generate about 600W to maintain body temperature? If we normally dissipate around 90W that would leave 510W extra. That’d be almost 500 kcal of energy an hour to maintain body temperature. That’s disregarding the convection properties of water in a running shower. Is that right?

Sounds about right. It’s possible to die of hypothermia in as little as an hour in 16C water.

I have a little booklet on hypothermia in my desk, it gives the following survial statistics for an adult in 16C/60F water:
[ul]
[li]Exhaustion / unconsciousness: 1-2 hours[/li][li]Death: 1-6 hours[/li][/ul]

From an earlier SD article: “Rinse with warm water, to open the pores.”

From: http://www.straightdope.com/mailbag/mshave.html
titled: Shaving seminar: (a) With the grain or against it? (b) Hot water or cold?
05-Aug-2003

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The shower v. bath part matters a good bit, since the surface area in contact with the cold water is much reduced in a shower. (It’s only hitting one side of you, and not all of that side – factor of 4 reduction in heat loss maybe?)

However, a shower will have a constant water temperature and convection as opposed to a bath, no?

I think the most efficient cooling would be bobbing up and down in the surf of the Pacific