Body battery accuracy increased with chest strap?

Hello Daniel.  I just noticed something while looking at my past activities that I find intriguing and have no answer for and I'm hoping you'll look to see if you have the same.  I went into health stats in GCM on the days of my activities and checked stress. I DO NOT have any stress readings during those activities and I'm using my FR 945 with a HRM-Tri.  I then checked body battery for the same activities and I see on the graph where it started to drop. Here's what I found interesting. On that body battery tab you can select stress to add a graph to the body battery graph.  I noticed during every activity, that body battery dropped, but then plateaued (flatlined) at the halfway mark of the activity no matter the duration.  Do you have the same? 

Hi Tess,

Yes mine behaves exactly the same..

I think there are still a few kinks in their algorithm experience.

If you read Brooks post on the latest firmware he verifies this with the sleep algorithm experience, so I am guessing stress and body battery are experiencing similar issues - just harder to pick up as it seems like "black magic" and not science to most people.. 

https://forums.garmin.com/sports-fitness/running-multisport/f/forerunner-745/243374/forerunner-745-sw-3-10---live-to-100

I am actually in the process of alerting Garmin-Brooks to the same issue you just asked me about as he asked for my reply then closed the thread so I had to PM him.  (The below link)

https://forums.garmin.com/sports-fitness/running-multisport/f/forerunner-745/242815/beta-forerunner-745-sw-3-09

Would probably help if it was all public.. 

Below you can see my 3hr bike ride, my heart rate was constant just over 150bpm for the entire ride yet there was a plateau in my body battery half way through??

https://www.dcrainmaker.com/2020/09/garmin-hrm-pro-chest-strap-depth-review.html

In the comments section Ray replies that no body battery or stress data are transmitted from the HRM Pro when connected to the app but HR is.  This is a different use case but the same results as I suspected (only HR is sent) when connected to the watch.  

Again with the New Garmin HRM Pro my Body Battery plateaued during a hard 2hr ride with a heart rate in zone 4 yesterday. It was on the fall all day long even when I did resonance breathing very relaxed (50 Heart Rate)... so how does it flatline during a hard effort??

The last test I did was go into the watches settings and connect the HRM-Pro chest strap. I still noticed that the sensors were flashing on the watch which in the literature says should be disabled.

As of today I am convinced that a chest strap does not in any way increase the accuracy of the body battery metric. In fact there is an issue where there seems to be a flatline in activities while wearing a chest strap..

Will still do a few more tests in the future but I think this question has been answered. I still believe body battery is a valuable metric and I hope a firmware update can make it more accurate and even more valuable one day. Thank you to all who have contributed in this forum and others.

The comments in this blog post are relevant:

Garmin HRM-PRO Review | The greatest ever could still be better (the5krunner.com)

Crispin Ellisdon states that the HR Straps data is appended to the end of an activity file.  So only after it is process in Garmin Connect is when the Chest Straps data is displayed.  Interesting for anyone that follows this thread. 

This would mean in real time much of the metrics eg. Stress are derived from the watch, and Garmin would only use the essential metrics that require the accuracy of the chest strap (HRV Stress TEST) to use the live data.

He is talking about swimming, where there is no connection available during activity. 

Hi Pavel, I did not get this from the comments section. It says this is normal behaviour every time the chest strap is attached which makes total sense for all activities. Try this test, put your chest strap on someone else (get them to sprint or do some push-ups) and check who’s Heart Rate your watch is displaying... It is exactly the same as the stress widget, this is displayed from the optical wrist sensor. It looks like the watch writes the HR as an extra field and this field takes priority over the optical heart rate when the activity is saved.

Check this post Pavel

https://forums.garmin.com/sports-fitness/running-multisport/f/forerunner-745/247693/no-stress-numbers-after-workout

There is even simpler test. When doing activity check whether LEDs on optical sensors are flashing (they don't)