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Running and thermoregulation: the post-run “shivers”

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I’m sitting here, preparing to write a blog post on thermoregulation. I finished a good run a while ago. The temperatures outside weren’t too extreme (50ish degrees F, so comfortable for a good run), and I was sweating freely when I finished. About an hour later, here I am, in fleecey pants, shirt, socks, hoodie…and sleeping bag. And afghan. And cat.

I’m freezing. Really, seriously cold. My nailbeds are almost purple, my hands are like ice, and I’ve got goosebumps all over. I’m almost too cold to shiver.

This happens every time I run more than about 5 miles. It happens winter or summer (I think winter is worse, usually in summer it’s a relief!). I’ll go out, run 5 or more miles, come home sweaty and glowing with my happy runner’s high, and about 30 minutes later, once all the sweat is dried, I’ll descend into what I call the “post-run shivers”. They last up to two hours after the run, and are the reason I keep my sleeping bag close to hand.

(What I feel like right now. Source)

When I’ve asked other runners about it, many of them are mystified. Some of them have only experienced the hot feeling post-run, and tell me they can’t shower immediately, or they’ll come out still sweating! But a few others know what I mean. And I’ve always wondered, what is happening to me? Is it normal? Is it ok?

When I learned about how humans regulate their body temperature, I learned that we have a natural temperature “set point” of around 37 degrees Celsius (98.6 degrees Fahrenheit), based in the hypothalamus of our brains, and your body regulates its temperature around that set point. When you get cold, your hypothalamus senses the temperature change by getting information from “cold” and “warm” receptors in the skin, and starts inducing mechanisms to reduce heat loss (shivering to make more heat and constricting the blood vessels near the skin to reduce heat loss, for example). Conversely, when you are hot, the skin temperature rises, the hypothalamus senses the change in body temperature, and induces mechanisms to promote heat loss (such as sweating and dilating blood vessels in the skin).

So what causes my shivering, even though it’s perfectly warm inside? I thought that perhaps my hypothalamic “set point” was off. The idea behind this is that there is a “set point” temperature which causes the hypothalamus to induce shivering or sweating, in order to maintain a set core body temperature within a very limited range. So I thought that perhaps, while I was running, my body was hot and giving off heat to maintain its set point of 37 degrees, causing me to sweat. According to this logic, when you stop exercising, your body should quickly stop sweating in an effort not to lose too much heat. My thought was that maybe my hypothalamus was a little slower, not catching on that I’d stopped working out, and continuing to give off heat until my temperature got too low, and I ended up cold as a consequence.

But I wasn’t sure that this was really true. So I got in touch with Ollie Jay, who runs an exercise physiology lab focused on temperature management at the University of Ottawa. And it turns out that, while we used to believe that our hypothalamus controlled everything via an adjustable “set point”, that may not be the case. While our bodies do maintain a set point, our core temperature fluctuates a bit more than we used to think and there’s a much larger variation in body temperature responses than we thought, and it’s the dissociation between skin temperature and core temperature that’s causing my current shivers.

Let me explain. When I start running, my skin is cool. Once I begin to run, my body begins to produce a lot of heat (running is a terribly inefficient mode of transport). But my SKIN is still cool. So the heat ends up stored inside for a short time, until my skin heats up, the heat loss mechanisms kick in, skin temperature goes up to cause heat to be lost to my environment, and if I continue to produce heat by continuing to run, I will start to sweat (which will evaporate and help me lose heat). However, even though I’m now releasing heat, my core body temperature is still a little elevated from the beginning. My body can now keep up with my current rate of heat production, but it can’t get rid of all of it. This means that my core temperature has risen, and is staying at a new, elevated temperature, while I exercise. This happens to everyone, but will vary depending on how big you are and how hard you’re working.

But what happens when I stop??

When I stop running, the heat loss and sweating will stop fairly quickly. But remember, my core temperature is still elevated. This means my skin temperature, though I won’t be sweating, will remain high and I’ll still lose some heat to the air. And because my heat production is down (I’m not running anymore), my heat loss is going to be greater than my heat production. At first, this is good because my core temperature is a little elevated, and this will lower my core temperature. As long as I don’t lose heat too quickly, Everything will go back to normal.

But in my case, I may lose heat too quickly. This can happen if you have a smaller mass. In my case, my BMI is 21, which is in the normal range, but I’m also tall. This means I have a relatively high surface area for my mass. Dr. Jay hypothesizes that my relatively high surface area will dissipate heat rapidly, and that I may keep losing heat even after my core temperature has come down to normal, overshooting the mark and ending up at a lower core temperature. This causes my cold temperature mechanisms to kick in, and I get cold, the blood vessels near my skin constrict (hence my purple fingernails) and I start shivering.

You can see that the temperature regulation mechanisms are the same, but what’s interesting about this relatively new idea of temperature regulation is that, while the mechanisms are the same, there is much more variability than previously thought. The core temperature of our bodies can rise and then fall a little as our conditions change, and there’s more variability in core temperature and in the degree of core temperature changes from person to person. It also means that we can’t just do research on things like exercise and body temperature in athletes. We also need to do it in unfit people, normally fit people, exercisers, non-exercisers, young, and old. Each of these groups of people is going to have a temperature response that could vary in a different way, creating different risks for different people. And these are further complicated by differences in body mass and exposed surface area. In my case, this variability means that I go hot and then cold after my run. And while it’s nice to have science explain the phenomenon, it’d be nice if it would get rid of the shivers as well!!

Thanks very much to Dr. Jay for giving me so much information and the reference for this post! For more on Ollie Jay and the work going on in his lab, you can visit his website here, and his Facebook: (I have to admit I’d love to participate in a study!).

Romanovsky, A. (2006). Thermoregulation: some concepts have changed. Functional architecture of the thermoregulatory system AJP: Regulatory, Integrative and Comparative Physiology, 292 (1) DOI: 10.1152/ajpregu.00668.2006

Scicurious About the Author: Scicurious is a PhD in Physiology, and is currently a postdoc in biomedical research. She loves the brain. And so should you. Follow on Twitter @Scicurious.

The views expressed are those of the author and are not necessarily those of Scientific American.

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  1. 1. yannisguerra 1:22 pm 03/28/2012

    Interesting. Do you have a prolonged warm-down period? That may be a solution, to increase the time after you finish the high intensity workup, so it gives time to your core temperature to lower slightly, while you are still producing some (but not as much) energy.
    Also, the website link for Dr. Jay is not correctly set up.

    Link to this
  2. 2. scicurious 1:47 pm 03/28/2012

    Thanks for letting me know, I think the link should be fixed. I do generally do a cool down period of about 10 min, but I guess it’s not long enough!

    Link to this
  3. 3. deevybee 2:56 am 03/29/2012

    This is fascinating! I’m intensely interested in human thermoregulation as I have an insane physiology that means I am often either too hot or too cold, or sometimes my head is too hot while the rest of me is shivering. And when I get into such a state I have a strong risk of migraine, so consequently I am very nervous about doing aerobic exercise for longer than about 10 minutes. In the past, when I tried jogging for longer periods, my face would go brick red and stay that way for an hr or so after the run, but then I’d get shivers – and an hour or two later a very bad head that could turn into migraine. Even now I’ve decided I’m just destined to be one of nature’s couch potatoes, I can still get this overheating and then shivering thing after a brisk walk of 30 min or so.
    My temperature control is also bad at night – often freezing despite multiple blankets, hotwater bottles etc when I go to bed, and then way too hot and sweating after I’ve slept about one hour. I don’t fit your BMI theory as I am overweight. I’ve often thought I must have some kind of reptilian genes.

    Link to this
  4. 4. Bee 9:48 am 03/29/2012

    I have this too, but I thought of completely other reasons. I’m not particularly tall, but my blood pressure is in the low regime and my rest pulse is also quite low. Running brings it up, but then it drops quite suddenly, leaving me shivering with blueish nails and goosebumps. I sometimes have this also without the running. But after running, you can add to this warm showering and cold drinks, probably contributing to heat loss. What helps me, somewhat, is showering cold (well… coldish) and drinking something warm, or at least not outright cold.

    Either way, interesting post. I hadn’t even known there’s a name for it!

    Link to this
  5. 5. ktarvin 12:18 pm 03/29/2012

    Thank you for this post! My husband and I both experience post-run shivers. We are both physically fit and healthy – we swim, bike, run, crossfit and and do crossfit endurance on a weekly basis. Our lab values and lipid profiles are within the normal range. The post-run shivers occur for us after a long run (>1 hr) or high intensity run/workout. We experience this less often after a bike or swim. Showering, changing clothes or adding layers, and hot tea help. We are usually cold for a few hours post-event/run. Overall, it’s a nuisance.

    Link to this
  6. 6. ollie_jay 2:46 pm 03/29/2012

    Hello Bee. May I suggest that your experience is not necessarily all that different from the phenomenon described in the post? It is still an issue with heat dissipation exceeding heat production to the point that your body sheds too much heat after finishing exercise and your core temperature consequently dropping below normal. However, the cause in your case may be that a greater amount of peripheral blood pooling (associated with your post-exercise hypotension) which would maintain muscle and skin temperature at quite high levels once you stop exercising. If this is the case, a high skin temperature would lead to higher rates of heat loss via convection and radiation and despite a reduction in sweating, your body ends up going into heat debt and your cold thermoregulatory responses kick in to defend a lower body temperature?

    For those interested in the work in our lab, you can also visit our facebook ( page (link in article does not work)

    Link to this
  7. 7. scicurious 2:50 pm 03/29/2012

    Sorry Ollie! I edited that Facebook link TWICE. One more time! :)

    Link to this
  8. 8. storm55 9:30 pm 07/15/2012

    Actually this might be a solution to that problem. Watch the video that talks about “Sports gear to turn sweat into energy”

    Link to this

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