More evidence that heat is in your head (or neck)


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- Alex Hutchinson (@sweatscience)


In the last month, I’ve posted about palm cooling, face-warming, and a study that suggested that some of the slowdown we experience in hot weather is attributable to the brain rather than body overheating. The latest addition to this theme: a study on neck cooling, published online in Medicine & Science in Sports & Exercise a few days ago.

The gist: Seven cyclists performed a 15-minute time trial in 30 C heat, after riding for 75 minutes to heat themselves up. They did it once as a control, once while wearing a “cooling collar” (essentially an icepack that fits around their neck while riding), and once with the cooling collar being replaced every 30 minutes to keep it colder. As expected, the cooling collar improved performance in the time trial by about 7% (this has been demonstrated before); but replacing the cooling collar didn’t produce any further gains, even though any cooling effect had disappeared long before the time trial started.

What’s most interesting is that there were no differences between groups in any of the physiological variables they measured — rectal temperature, hormones like seratonin and dopamine, lactate levels, etc. The differences appeared to be purely perceptual:

It has been proposed that during self-paced exercise the intensity is regulated by a complex network of feedback and feed-forward systems regarding the physiological state of the body to allow for the completion of the task within homeostatic limits. The data from the current study and from a previous investigation using the same protocol suggest that cooling the neck enhances preloaded time-trial performance in a hot environment by masking the extent of the thermal strain…

Or, to put it simply, it’s in your head. That doesn’t mean that heat doesn’t have real physiological effects — just that, in most cases, our brains take the heat into account to slow us down prematurely.

strain9The critical core temperature and central governor theories are the two main theories proposed to
explain the impairment in sporting performance observed in hot temperatures and both models propose that there are
mechanisms in place to prevent the onset of a dangerously high internal temperature

7 Replies to “More evidence that heat is in your head (or neck)”

  1. Do you think there could be any downside to this – e.g. is there a good reason why the body shuts things down in the heat? In general I think people spend a lot more time worrying about heat stroke than they should, but I’m wondering if this might still be a bad idea, as compared to something that actually reduces whole body temperature.

  2. I am profoundly disappointed there was no “hot under the collar” joke. Otherwise, great work as usual.

  3. Thanks, Todd! And John, I can’t believe I missed that one. Brutal!

    Travis: Good point — and really, I need to emphasize that heat is real! People really do get heatstroke, and in rare cases even put their lives in danger from overheating. It’s one of those messages that needs context. 99% of us are more cautious than we need to be in heat, but there’s still the chance of running into physical limits.

    In fact, I blogged about some research last year that seemed to do exactly what you’re warning about: allowing people to push beyond the usual “critical temperature,” thus potentially endangering themselves. From the results I’ve seen so far, interventions like palm cooling and neck cooling simply aren’t that powerful. Their biggest effect is to alter your pacing strategy early in the bout of exercise (so you don’t slow defensively before you’re actually hot), rather than allowing yourself to push farther into the danger zone once you’re already hot.

    Bottom line: your concern is a good one, but my sense is it’s not an issue with these relatively minor interventions, compared to taking drugs like bupropion.

  4. Hi Alex,
    Great timing for this, as I and a lot of folks are finishing off some “long runs” prepping for marathons, with the summer heat going up. On two recent runs of 16+ miles in 80+ degree heat, I “bonked” even though my legs were strong. To me, it felt like fatigue in my head, with some light-headedness (don’t worry, no cardiac issues!) I chalked it up to dehydration, but still aren’t sure.
    I’ve been reading interesting, similar stuff in Matt Fitzgerald’s book “Brain Training for Runners”, where he discusses how the brain will shut you down with fatigue messages well before your physiological tank is on empty. This, according to Matt, is a self-preserving safety switch that runners need to learn how to extend with training, but not ignore. Your thoughts?
    How’s the book doing?

  5. Apologies in advance, but am I the only one who thinks of the South Park “It” episode when this study’s protocol is discussed?

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