What is the technical reason wrist HR would produce an incorrect high HR?

Former Member over 6 years ago

I know this topic is well known, but I'm trying to understand how the wrist HR can significantly over estimate HR.

Example, if I slowly start climbing stairs, my HR jumps to around 155 and 160 within only 8 to 10 steps..

However, my true heart rate based on HRM run strap is only between 95 and 105. If I climb stairs for hours at that same pace my HR doesn't go above 115...

What is the technical reason wrist HR would produce an incorrectly high HR?

I understand low, but why would it over estimate?

Is there any possibility this wrist HR technology can be revamped to not be so awful? I'm starting to wonder if there is even a reason to use the watch without an HR strap at all times...

0 mcalista over 6 years ago

If the watch is too loose, external light can enter the sensor, which can interfere with the readings. If this happens rhythmically with your arm swing, you can get "cadence lock", where the sensors pick up on the frequency of external light entering the sensor with each arm swing.

Tightening the band, and positioning the watch on the fleshy part of the wrist can create a better seal against external light, and also provide a deeper blood supply for the sensors to pick up on your genuine pulse.

I find I need to have the band one notch tighter for accurate HR while running, than I do for 24/7 monitoring.