Feet = Thermostat?

Factual Questions
1

For my entire life, I’ve noticed something that I thought odd - essentially, no matter the temperature of the rest of my body, as long as my feet are at a comfortable temperature, I can bear the rest. Although it applies to all settings (Hot outside? Put my feet in the pool and I’m fine. Cold? Warm shoes/socks and I can go in short sleeves.) it’s most noticeable at night when sleeping, which I do with one foot out from under the covers so that if I’m too hot in the night, I still “feel” comfortable (mostly when the SO has a ton of blankets/comforters/heating blanket on).

I used to think I was alone in that regard, but I’ve mentioned it to others (usually men, but a few women too) and they all agree and have similar experiences. So, is there some scientific reason why feet seem to be temperature regulators (maybe like a heat exchanger?), or is it all in my head?

Speaking of head, it seems that the same effect would be achieved just by having my head out from under the covers, but that doesn’t work.

2

I do the exact same thing. I start out warm, but later at night, I get cooler, and pull the foot in.

3

My father used to do that same thing, Werekoala.
I am different, but he always slept with a foot sticking out of the covers to regulate his temperature while sleeping. :slight_smile: Thanks for the memory.

4

My feet can’t stand cold, but its my head which can’t stand being too hot.

Problems with your feet may be circulation related, eg blood flow cut off, eg frost bite,
so it pays to “answer their call” if they feel cold.

5

My feet are definitely the most temperature sensitive part of my body, and it’s not unusual for me to have a hot water bottle on them whilst I’m sitting on the couch of an evening. But I’m not like you, if the rest of my body is cold, warm feet alone won’t make me comfortable.

6

When your body is cold, it will concentrate heat everywhere but your extremities. Thus, when your feet are the right temperature, so is the rest of your body. That’s the only scientific explanation I can think of.

7

There’s a lot of larger blood vessels close to the surface on your feet too, which makes them great radiators for your body.

Too hot, expose them to colder air or water and your blood will shed its heat more efficiently and cool you down.

Vice versa for cold feet. Real cold feet, not the proverbial kind. Hot water or socks will never make marriage make sense.

8

This could be due to poor circulation too (or just your physiology).

With poor circulation, blood will tend to pool around your feet.

9

As it happens, recent threads have led me to read up on temperature regulation. I’ll summarize some relevant bits of what I’ve read, then speculate recklessly.

Body temperature regulation is directed by the hypothalamus. It secretes hormones that trigger various temperature-adjustment activities in the body based principally on two factors: blood temperature (which it senses directly) and skin temperature (which is relayed to it by the reticular formation).

Obviously, skin and blood temperatures can and often do differ, sometimes for reasons unrelated to temperature regulation. (For example, if you’re scared, the body tends to restrict blood flow to your skin and extremities–metaphorical “cold feet” may well cause literal cold feet.) When the two sets of temperature information are at variance, the hypothalamus has to weigh the importance of each. Logically, one would expect blood temperature to be weighted more heavily, and for what it’s worth, I found a study that seems to me to suggest this in rats.

That doesn’t mean skin temperature gets ignored however, and–WARNING: here begins speculation–it’s likely that it’s a proportional analysis. That is, the closer your blood temperature is to the hypothalamus’s target, the more weight is given to skin temperature. So, if your core temperature is right, you should be able to strongly affect the composite perceived temperature by relatively minor manipulations of the skin temperature information.

So, say you’re under the covers. Your blood temperature is spot on, but your skin is saying it’s a little too warm. You stick a hand or foot out from under the covers, and it starts sending back the message that it’s cool. The hypothalamus looks at a sort of weighted average of this information and says, “It’s just right.” As long as it thinks that, it doesn’t send out any of the hormones that trigger you to do temperature-adjustment stuff, so you stay comfortable.

Still more speculatively: Your feet are probably the part of your body most subject to external temperature variation: they’re farther from your heart and your hypothalamus than anything else, and they’re prone to circulation restrictions, as others in the thread have pointed out. It’s possible that the hypothalamus treats your feet as early warning sensors of a sort, weighting skin temperature data from them more heavily than from parts nearby, like your hands or face. That might mean you could manipulate your temperature perception more easily with your feet than with your hands.

10

I use feet for some temp control while sleeping.

Also shoulders. Take old “T” shirt and cut to about 6" long so just your shoulders & underarms are covered & between that & foot control of some light covering is all I need between too hot to sleep at all and so cold I need a comforter.

Female feet have used my back for foot warming ever since I discovered girls in my bed was a good idea…