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Heart Rate in Cold Temperature?

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  • Heart Rate in Cold Temperature?

    I recently picked up a used Apple Watch that measures my heart rate. Figured I’d test it’s limits while pushing mine and took it out with me on a camping trip the other week. It seemed pretty accurate tracking activity during the day.

    It might have hit zero degrees during the night. It was a bit colder than I was expecting and I was a little chilly in the system I brought, but not super uncomfortable. The watch, however, kept waking me up with a low heart rate warning starting I was dropping below 40 beats per minute. It’s not unusual for me to hit in the 50’s at home in my sleep, but 30’s seems too low.

    Anyone else experience anything like this?

  • #2
    Could it be that when your sleeping cold the sensors are less accurate? The body constricts the blood vessels in our extremities when we get cold, that is part of the reasons feet can be hard to keep warm when sleeping. For the hands, they may not feel as cold because they are heated by the core but the blood flow might be dropping below the sensor’s limits at times.

    Just a guess, I would love to hear of anyone else has seen this.


    • #3
      if those are your "normal" heartbeats, I'd suggest getting to a cardiologist, you may have bradycardia, which can be magnified by the cold and lead to a stroke.


      • #4
        I have noticed a drop in my samsung watch while outside or when the watch is cold. Possible it's the technology that has an error factor at a given temp.

        Possible it doesn't read a pulse as well either when it's cold.


        • #5
          I’m pretty active, but was a bit worried about bradycardia. Long story short, don’t think that’s the issue. I also kept my hands and arms down inside the sleeping bag and pod system next to my body, and it seemed to be working well outside all of that during the day. Will test again, but this weekend is a bit to cold for such a test (sunny afternoon, but -11 with wind chill of -35, tonight is sure to be even colder). But


          • #6
            Been out several times since. Although I’ve changed my set up a bit and likely has a few problems adjusting and whatnot, I feel like I have everything working the way it should. However, still dropping below 40 bpm heart rate by the morning if the temp gets low. No other physical symptoms, or recognizable mental defects; besides continuing to sleep outside in a hammock while others are worried about their cars starting!


            • #7
              When a product is made with ho-hum everyday consumer electronics, it is likely to give whacked readings when temps get too high, or too low for the said device to handle. Mil-soec electronics will give you a much higher degree of accuracy in temperature extremes. That said, I say also err on the side of caution as it might be your body. Some people do have lower blood pressure naturally, and some higher, again naturally. Investigate your possibilities.

              You could test your electronics by subjecting to heat or cold whilst wearing the ‘watch’, while you are yourself at normal temperature. For instance have it check your heart rate, then subject it to an ice cube in a bag- if it goes haywire giving you alarms, it could just be those ‘top rated components’ in your device. 😬


              • #8
                several years ago I had a massive heart attack, which gave me the opportunity to wear a medical grade monitor over the winter, if anything I found that both heart rate and PB were slightly elevated in the cold. The cardiologists explained it was because the heart works harder to force your blood through cold, constricted arteries and veins. I would suspect the electronics and position of your watch are contributing to faulty readings, real monitors are placed over your heart, not 3' away, Even the O2 sensors can give different readings on different fingers due to injuries or variations in your circulatory system.
                Bradycardia is very serious and can very quickly and easily lead to organ damage and stroke, I have it (contributing factor for above), and MUST be taken seriously because if your heart is not pumping fast enough, you are starving your tissues for oxygen AND you're not carrying heat from your core to your extremities which can lead to cold injuries. Even an extremely fit athlete has an average RHB of 60, any lower than 50BPM is dangerous or even fatal and needs to be monitored and controlled.
                Take it from someone who's been there, you DO NOT want to go through what I did (and still am)