Inaccurate Exercise Load using Polar OH1

Additional test, rather easy bike activity - FR945/WHR vs Edge530/OH1, HR zone settings are the same.

Edge530 HR:

Edge530 time in zones:

Edge530 stats:

FR945 HR:

FR945 time in zones:

FR945 stats:

Everything but training stats seem to be quite close (although it's not as dramatic as during higher intensity activity). OH1 data are smoother.

Obviously I don't have 2nd FR945 for ultimate test but prior bringing this to attention of Garmin I'd like to test FR945+Garmin chest-strap vs Edge530+OH1, then probably other way round. Other ideas?

I did FR 945 + Garmin Chest strap vs. OH1 vs. Wrist with the same route and intensity. OH1 is much lower than Chest strap or Wrist. Chest strap is pretty much the same load as the one from the wrist. 

Have you tried to extract HRV from the .fit file for OH1 to see if this is recorded? At least the chest straps transmit the R-R intervals. I wonder if the OH1 does the same or transmits some averaged HR. Since R-R is need to calculate breathing frequency needed for EPOC and load, that might be the difference. According to Polar the H-series is neeeded for R-R....

Please could you give me some kickstart  how to extract the data? I've tried gebabbel on Linux and that complained about invalid data length. Neither some online tool for repairs able to export to CSV worked.

I can see RR with OH1 recorded activities (absolute figures are incorrect but it seem to be catching spikes). On the other hand FR945/WHR doesn't record that and provides EPOC estimates too. I can't find anything from FB saying it's taking into account RR.

5082041 said:

At least the chest straps transmit the R-R intervals. I wonder if the OH1 does the same

Optical HR does not and cannot measure R-R intervals; that's a function of the electrical signal of the heart. Optical HR detects the peaks, or interprets what it believes to be the peaks of the pulse wave which it detects by a change in the amount of light reflected as blood volume changes beneath the skin. This is actually called the P-P interval and unlikely ever to be as accurate as the R-R interval measured from a heart beat but software attempts to fill the gap.

Yes, you're right though it is beside the point. If Garmin load really is based on EPOC, they need intervals to estimate the breathing frequency, otherwise no EPOC. I can imagine that the OH1 data is not sufficient to do that properly or is not subjected to the "fill the gap" algorithms like for WHR.

There is a white paper from FB describing "Indirect EPOC Prediction Method Based on Heart Rate Measurement". It's all based on R-R intervals which are needed to get breathing frequency and HR. The whole load thing is strange, as I am not wearing my watch during exercise and the HR belt is switched off when I stop the activity. I still get a load, but can't be based on EPOC as the watch does not get HR data after exercise. And predicting an anyway model based EPOC during exercise sounds even more weird. I wonder if they have a programmed fall back strategy to calculate some TRIMP if data is insufficient.

I use the FitToCSV tool (written in java) from the ANT SDK from https://www.thisisant.com/resources/fit-sdk-beta/. It is free and will work on Linux but unfortunately the included Windows batch files will likely not. I've rewritten one of them to get the HRV R-R intervals out in a better format than the strange separation by the | sign you get natively. It's a great tool for me.

Off-topic, sorry: Basically the ability to get the fit files directly from the watch and convert them easily to CSV is the reason why I am staying with Garmin for the moment. Due to the complete black-box calculations of load from Garmin (and Polar, too) I calculate the load and other parameter myself. It works well and with an established excel table and it is even faster than upload the activities to Garmin connect. It also made a change from Polar to Garmin possible without thrashing all previous training data as the load calculations are different. Unfortunately wko5 and similar don't work for my sports.

Hi thank you so much! I'll have a try with BLE and see how it goes. No I haven't found out a solution yet but this sounds very promising!