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Resting heart rate - how is it calculated?

tboooe
over 5 years ago

According to the Garmin website, resting heart rate is calculated during sleep (see below).  However, I have found that the RHR can sometimes decrease if during the day my heart rate is lower than what the watch calculated during my sleep.  For example, the other day I had a really restful period where my HR according to the watch was 43.  Up to that point my daily RHR was showing as 48 but afterwards, it changed to 43.  The odd thing is that this does not always happen.  Sometimes the watch seems to take my lowest HR throughout the day as my RHR, while other times it only seems to only use the calculation method described below even though my HR during the day drops to below it.  Anyone know exactly how RHR is calculated by Garmin?

RHR: This value is for the current day. It is calculated one of two ways. For users that wear their watch while sleeping, the watch will read and record the average of all readings while they sleep, excluding periods where any steps were detected or the measured heart rate falls outside reasonable bounds. A minimum of four hours of sleep time is required to register a reading. For users that do not wear their watch overnight, RHR will be far less accurate and a rough estimate will be determined based on the lowest average reading over a one minute time period during the day.  

  • 0 over 5 years ago

    one thing i know for sure: totally different than Apple (usualy 4-5 bpm lower) or Fitbit (usually 4-5 higher, even though the RHR for sleep period is identical to Garmin)

  • 0 over 5 years ago

    I believe it takes a rolling time-average and looks for the lowest sustained HR over a period of time. It allows for non-sleep HR because it is possible to have a bad night (illness etc) and for the daily RHR found in daytime. I've had a Garmin for a number of years, and it's RHR for me is far more believable than other devices I have had (such as Samsung) because it samples more frequently

  • 0 over 5 years ago in reply to Ɛpsilon

    I agree.

    Despite Garmin's information posted in the OP suggesting otherwise, it has always appeared to me that the RHR is whatever your lowest HR was that day, as averaged over the course of a rolling minute.

    So your HR might get as low as, say, 39 BPM at one point, but it will not register that as your RHR unless it averages 39 for a whole minute straight. This is to prevent it from registering anomalies in your variable heartrate as being your actual RHR. The rolling 1-minute average mimics the way you would check your own RHR manually, with a finger on your pulse and a stopwatch, where you're not timing how long between each pulse, but rather counting how many pulses there were over the course of a minute.

    While RHR typically happens during sleep, it can happen sometimes where you actually achieve a lower heartrate while awake than you did in sleep. In those cases, in my experience, the Garmin will always use that as my new RHR for the day, rather than what it measured earlier in the day during my sleep.

    So it appears that Garmin is actually slightly incorrect in their information above, because when RHR is taken during sleep it does not appear to overrride any lower RHR's that get registered throughout the day. And I'm fine with that, I think that's the way it should be.

    This is also, by the way, the reason why your daily "high HR" is often lower than what an activity you recorded that day says your max HR was. The activity is measuring the time between each individual pulse, and the fastest time between any 2 pulses is what your max HR for that activity was - whereas, your daily high HR measurement is measured using the same rolling-minute-average as RHR uses, so it will almost always be slightly lower than the max HR you recorded in an activity that day.

  • 0 over 5 years ago

    Thank you everyone for the replies.  While I agree that it seems the watch uses the lowest heart rate achieved during the day for at least 1 min, this does not happen consistently for me.  Sometimes my lowest heart rate during the day is several beats lower than what was measured during sleep but the watch still reports my RHR the one calculated during sleep.