Heart Rate Drift, Temperature, Recovery

  • Creator
    Topic
  • #28603
    pshyvers
    Participant

    Hi folks,

    Tried to run a heart rate drift test of AeT today. Got pretty massive decoupling (20%), despite extremely easy breathing and very relaxed perceived effort. At the beginning I was running 8:00 @ 155bpm, by the end I was at 12:00 @ 165bpm and couldn’t get my heart rate down any lower. (MHR 204)

    I’m certain the results are bogus- I do not normally decouple anywhere near that much- but I’m not sure exactly why. I wasn’t totally recovered & fresh, and I was in a deeply fasted state, but that doesn’t seem like it would fully explain it. My chief thought is, it happened to be over 90F & I might have been slightly dehydrated. Temperature affects performance- but can it affect performance this much?

    Bonus question, I sometimes feel like my HR gets “hung up” in the low Z3 range and it’s difficult to get it to drop below ~160bpm. Is this a sign of anything particularly interesting? E.g., is the lactate shuttle falling behind and keeping HR elevated even as load drops?

  • Keymaster
    Scott Johnston on #28614

    Heat will have EXACTLY the effect that you saw in this HR drift test. When your core temp gets out of its normal comfort zone the capillaries in the skin dilate and much more of your blood volume get shuttled to the skin to dump heat. That leaves less for the working muscles. The heart responds by increase it rate of contraction to try to keep up the demands for O2 in the muscles. The result is increased HR and perception of effort.

    Getting your HR hung up in Z3 is usually a sign of aerobic deficiency.

    Scott

    Participant
    pshyvers on #28615

    Got it, so essentially the HR is increased in hot environments somewhat independent of the training load due to cooling needs. Fascinating bit about the blood vessel dilation, I can see how the dots connect. So in those environments, HR is probably not a very reliable metric (unless perhaps you are well conditioned to the heat?)

    Thanks, figures. Used to happen a lot more, much less common for me anymore but noticed it today. Perhaps one way to take it would be that my aerobic capacity is adequate in cool weather but not yet fully developed enough for the additional demands of hot weather.

    Participant
    briguy on #28638

    [quote]So in those environments, HR is probably not a very reliable metric[/quote]

    If you’re doing HR zone training, then you can still rely upon it. Just means you slow down to stay in zone when the temps require it. I run in the Southeast US, heat/humidity is a factor 9 months out of the year.

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