Stress vs HRV Stress

The oHRM will not be as accurate as a strap.  Is the 18 reading in the stress widget after doing a stress test with the oHRM?  The HRV stress test with a strap will be your current level, where the widget is showing your all day stress level averaged from midnight to present time.

I have not seen an ability to do a stress test with the optical HRM; whenever I select the stress test activity it says that a chest strap is required.  I've only had the watch for about a month, so I am sure there are features I haven't learned yet. 

So if the widget is showing my stress from midnight to the time that I took the test, which was about 8:30 a.m. and it showed 18, and I did 3 HRV stress tests back to back at the same 8:30 a.m. time period which produced results of Moderate, High, and Very High all within minutes of each other, is this normal behavior?  What would cause such dramatic minute by minute changes to HRV stress when using a chest strap?  Even if the optical HRM stress measurement is less accurate than the chest strap, shouldn't they be somewhat in the same neighborhood?

Thank you

Fair question. I can indeed only use the HRV Stress app with a heart-rate strap attached. I haven't used a chest-strap for some time and it seems the battery has died, so can't check the difference now.

However, when not moving, the measurements from the oHRM and the chest stap shouldn't differ much regarding hart-rate. Only thing that I can think of is that the chest strap measures more parameters than the oHRM. That leads me to believe that the calculations in the HRV Stress app use an entirely different algorithm than the oHRM widget.

Given the wide variety that you see in your measurements, I would doubt whether the watch is actually able to provide reliable data on your stress level.

eberends said:

Only thing that I can think of is that the chest strap measures more parameters than the oHRM

The chest strap reads the electrical signal from the heart which has well-defined R-R intervals - think of these as sharp peaks and easy to 'see'. The optical heart rate sensor is looking at a waveform with rounded crests thus the P-P interval (pulse rate variability) is less well-defined requiring more 'interpretation' from software.

HRV is frequently analysed in a quiet environment for at least 5-minutes in order to remove some of the artefacts from instant measurement. It is quite possible to see changes from one reading to the next if taking measurements in a more dynamic environment.

I dont know the second device, but high HRV would indicate low stress. Is it possible that the chest strap is giving you values of HRV and not converted to level of stress?

There is no discrepancy.  When stress is low your HRV should be high.  When stress is high HRV should be low.