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Why does wrist based heart rate differ between profiles?

Former Member over 4 years ago

I did hope my 945 wrist heart rate would be better than 735. It's worse!

But what I have discovered is puzzling me. If I do a typical outdoor HIIT class using the cardio in built profile, my heart rate will be approx 20-30bpm to high. Now the other day I created a new profile, using the same metrics/data screens as cardio. It records heart rate about 30bpm too low! However, if I go cycling or running, heart rate is pretty accurate. I also have a chest HRM to check accuracy, but it's a pita for a lot of activities, falling down.

I know there have been plenty of threads about poor wrist based heart rate, but why the different readings per profile??

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0 gtom over 4 years ago

Did you try making a copy of running profile, rename it to Cardio HIIT and record your session? Is the reading still accurate or off again?

0 Dr Phil over 4 years ago

Because it would appear Garmin are trying to be clever and adjust the heat rate detection to suit the activity:

"Additionally, HR is calculated differently for each activity. Use the activity app that matches the activity being done. For example, using the Elliptical app while running outdoors could result in incorrect HR being recorded."

Best thing you can do is to contact Garmin Support and let them know.

0 Former Member over 4 years ago in reply to gtom

No, I created a completely new profile using "Other"

0 Former Member over 4 years ago in reply to Dr Phil

Interesting reading the article about different activities. Maybe the weights (often kettlebells) could be affecting the reading. I'll try downloading a HIIT app or I just found a Cross training one.

0 ForeKing over 4 years ago

Optical HR is known to be inaccurate when doing HIIT or running activities etc. Garmin uses software to make this better. For example if you select a running activity and you are resting with a 60 bpm HR. There is a very good chance the software will say your HR is 120 bpm because it assumes the sampling is off and it is impossible for any human to run with a 60 bpm HR.

You can extrapolate this thinking to other activities. Garmin mentioned activities that use your forearm muscles are calculated differently because flexing affects HR. I've tested this thoroughly while wearing a chest strap. Garmin HR is accurate, but if you select the wrong activity it WILL be off.

For best results 1) use a chest strap. These are extremely accurate and are not expensive but potentially uncomfortable. 2) make sure watch is tight on wrist but not too tight. If I wear my watch 8 notches during activity HR is spot on, but if I wear it at 9 it is off. This difference is a few mm. You need to figure out what is the right tightness for your wrist. The right tightness is NOT what is most comfortable but what gets the best reading. I highly suspect you aren't wearing the watch right for HIIT and it needs to be tighter. If you are non-white (like me) optical HR has the potential to be eve less accurate when not worn appropriately.