Strange RHR Formula by Garmin

Former Member over 8 years ago

I was trying to figure why Garmin calculation of RHR was so different to the manual one I was taking at the beginning of each day..... then I found this!

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

I really don't understand the logic of taking an average of you heart rate throughout the night (12am - getting up). Your heart rate is always higher at the beginning of the night as the liver and kidney's filter out toxins and stress hormones fall to a normal level. For me, it's normally 3:30-4:00am when the heart rate levels out and remains at a steady level until I get up. The time you would normally take a manual reading. I haven't found anything online that would suggest taking an average of your heart rate while sleeping.

This issues has also been discussed on the forerunner 235 forum

What it means is the data collected isn't as useful as it could be. it always seems to be about 4-5bpm out on average. This wouldn't be a problem if you could manually override the figure with the heart rate immediately after waking, or even have it as a menu option to enter manually or take reading X amount of minutes before first getting up. There is also the issue of increase heart rate during REM that is perfectly normal but could also affect your RHR.

Interestingly though, one option (if you want to record sleep data) is to sync the watch when you wake up and then restart the watch. This clears the data and forces it to record the lowest heart rate for that day.... which is far more accurate that then nighttime average (form me). There are a number of times during the day when my heart rate falls below the current RHR calculation but is completely ignored.

Anyone else noticed this?

0 ThiagoSian over 8 years ago

Yes, I also get lower RHR during the day lower than the "RHR" of the day.

BUT, if every day its measured with the same logic, I guess it does still valid, as you still able to detect higher RHR measurements and then try to figure why that happened.

0 Former Member over 8 years ago

Yes, I also get lower RHR during the day lower than the "RHR" of the day.

BUT, if every day its measured with the same logic, I guess it does still valid, as you still able to detect higher RHR measurements and then try to figure why that happened.

I know what you mean but, the Garmin average is up and down like a yoyo at times but the reading taken in the morning is fairly steady. Also, when using the RHR to work out HR Zones, you want to use an accurate one otherwise it can throw out other performance and recovery stats. If they just made it editable like the sleep start / end times it would be spot on. People who just want to take the average can leave it while others who want to use the waking RHR can adjust it.

Edit. Incidentally, restarting the watch after syncing sleep data does seem to work. The watch has now picked up the lowest (1 min avg) heart rate from during the day, which again was 5bpm less that the night time average.

0 mcalista over 8 years ago

If they just made it editable like the sleep start / end times it would be spot on. People who just want to take the average can leave it while others who want to use the waking RHR can adjust it.

Actually, you can directly set it. Settings> User Profile> Heart Rate> Resting Heart Rate

You may also want to set this in Garmin Connect.

Note that the little graph in the widget will still show the Garmin overnight formula.

0 Former Member over 8 years ago

Guys, really true RHR - it's average heart rate 2-3 minutes after wakeup!
Not daytime measurements at rest, not night. Only morning. Better also measure blood pressure.

Moreover, the measurements made by the optical pulsemeter are complete crap. In comparison with HRM Tri, lies an average of 3-4 beats higher.

+1 but to start with, it would be good for Garmin to provide the option to take the RHR in the morning as you say. Forcing it to look for the RHR throughout the day is the best out of a bad bunch but atlas it seems more accurate than the current "Nighttime Average"

Actually, you can directly set it. Settings> User Profile> Heart Rate> Resting Heart Rate

You may also want to set this in Garmin Connect.

Note that the little graph in the widget will still show the Garmin overnight formula.

Yeah I do this now but that doesn't keep a record of the past RHR's, just the current one.

0 thigger over 8 years ago

Has anyone noticed this change since 4.1?
I didn't deliberately update my watch (5X) but it's suddenly on 4.1 and my reported RHR has plummeted as it's now using the lowest during the day rather than the overnight average.

0 meste7 over 8 years ago

Has anyone noticed this change since 4.1?
I didn't deliberately update my watch (5X) but it's suddenly on 4.1 and my reported RHR has plummeted as it's now using the lowest during the day rather than the overnight average.

Yep, found myself updated through BT. Re RHR I cannot say, my figures seem to be as before. But will keep an eye on it.

0 thigger over 8 years ago

Today it seems to be back to normal again (ie overnight average HR). Presumably when it updated the firmware it "forgot" that it had already calculated RHR from overnight readings and decided to go to the other algorithm (ie lowest average for a minute or whatever it is). Makes the graph look very confusing as my resting HR from the daytime is about 10 beats lower than my overnight average.

0 Former Member over 8 years ago

Today it seems to be back to normal again (ie overnight average HR). Presumably when it updated the firmware it "forgot" that it had already calculated RHR from overnight readings and decided to go to the other algorithm (ie lowest average for a minute or whatever it is). Makes the graph look very confusing as my resting HR from the daytime is about 10 beats lower than my overnight average.

I've just started to sync the watch as I get up and then restart it. That way I get the lowest 1min value for the day without losing sleep data. That seems to be closer to my actual RHR than the overnight average which is about 5-8bpm more than my waking HR.

0 thigger over 8 years ago

Do you mean restart the watch as it's syncing?

I'm not quite sure which I prefer - I quite like having a value in the morning, and my average HR overnight seems to be meaningful in terms of whether I'm recovering from training (though if I do a late session then I can see it takes a few hours overnight to settle down which skews the average). Also I work in a hospital and having the watch off my wrist occasionally gives strange readings (I could manually turn the OHR off but that's a pain). I'd probably prefer "lowest average for a minute overnight" or something. I guess the best solution would be for Garmin to let us choose as it's strange having both types of data in my charts - like you my overnight HR and resting HR are quite different.

0 Former Member over 8 years ago

Do you mean restart the watch as it's syncing?

I'm not quite sure which I prefer - I quite like having a value in the morning, and my average HR overnight seems to be meaningful in terms of whether I'm recovering from training (though if I do a late session then I can see it takes a few hours overnight to settle down which skews the average). Also I work in a hospital and having the watch off my wrist occasionally gives strange readings (I could manually turn the OHR off but that's a pain). I'd probably prefer "lowest average for a minute overnight" or something. I guess the best solution would be for Garmin to let us choose as it's strange having both types of data in my charts - like you my overnight HR and resting HR are quite different.

No. Let it complete the sync so all your nighttime data is store, then restart. You'll have a RHR figure in the morning but, it will then adjust it should your HR fall under that amount for one minute that day (12am - 11.59pm). It's the 2nd of two options in Garmin manual (see below).

For me, this has been closer to my actual RHR as the night time average is normally 5-8bpm more. When you look at night time stats, you'll see your heart rate is higher as it recovers from the days stresses and filters out toxins. It then stabilises, between 2am-4am depending on whether I've been out on the bike the previous day.

The ideal would be able to enter an amount manually taken just after you have woken but before getting out of bed. An accurate RHR is helps get the right HR zones. Using max HR only I found I was sat in Z4 & Z5 a lot, even though I didn't feel like it was that high. Now entering an accurate RHR the percentages in each zone reflect the effort I feel I'm putting in.

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