When people do exercise outdoors in winter at temperatures less than zero degree celsius, their hands are quite cold and hurt for about half an hour. Then, there is a sudden rush of blood into the hands and they are warm afterwards, just as if they are indoors all along. Why does this happen and is there anything one can do to trigger the warmth faster?

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    $\begingroup$ Probably because your body is now trying to get rid of heat after 1/2 hr of exercise. $\endgroup$
    – Solar Mike
    Dec 10 '20 at 22:23
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    $\begingroup$ Why is it not a gradual process and happens so suddenly, like a some valve is opened and warm blood flows into my arms? $\endgroup$
    – dinesh ygv
    Dec 11 '20 at 6:10
  • $\begingroup$ That valve being opened could be the capilliaries opening, well expanding, allowing more blood flow... $\endgroup$
    – Solar Mike
    Dec 11 '20 at 6:17

Cold extremeties are a reaction of endotherms where they reduce warm blood circulation to prevent losing core body temperature, otherwise the cold blood in your hands would lower your central blood pressure from 37'C, which makes the body less efficient and at risk of catching colds.

enter image description here

The reaction is called vasoconstriction.


Active cutaneous vasodilation occurs via cholinergic nerve cotransmission and has been shown to include potential roles for nitric oxide, vasoactive intestinal peptide, prostaglandins, and substance P (and/or neurokinin-1 receptors). It has proven both interesting and challenging that no one substance has been identified as the sole mediator of active cutaneous vasodilation. source

The above research can give you some clues about exercise and cold hands: enter image description here

When you have exercised for 30 minutes, the above quote applies, and perhaps there is also a hormone contribution from natural opiates, endorphins, and other chemicals like nitric oxide.


The endomorphin peptides, endogenous ligands for the mu-opioid receptor, and nociceptin (orphanin FQ; OFQ), an endogenous ligand for the ORL1 receptor, have substantial vasodilator activity. source

For some very good reading on the subject, search for "thermoregulation vasodilation", the corresponding pages give advanced general knowledge of the biology.


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