Actual Stamina in basic running training has become noticeably lower than Potential Stamina

I turned off Stryd and turned on Garmin's native running power. True, I did a not very long workout at the stadium - Basic workout from Garmin's daily recommendations. Training efficiency corresponds to actual sensations. Stamina decreased at the same time as Potential Stamina. I think the main problem with false data and estimates is the use of Stryd

Interesting. I am also using Stryd. Have contacted them? They tend to respond fairly quickly if you report a problem. I will try what you did and see if it makes a difference. 

But as I see it Garmin is overestimating the hard runs and underestimating the easy ones. Stryd power is lower than Garmin based on how they compute. But it would seem peculiar that the effect would be opposite at hard runs vs. easy ones.

I can confirm your finding that Stryd is causing the problem. Here is training load and effect with and without stryd.

I was also surprised by this. but it is not clear how the algorithms work

it seems that you are underestimating the load with Stryd on

Yes it seems. This could be reasonable if power was used in calculating training load as Stryd power is about 70% of Garmin values. 

But I though training load was using EPOC hence related to heart rate and VO2max. But it looks like Garmin has made some major change to the algorithm.

Anyhow, I have reported the problem to Stryd. Let us hope for a response from them.

they'll say it's not their problem, it's Garmin's, and that's true. And Garmin is unlikely to meet Stryd users, especially since they are their competitors in terms of running power. I really like Stryd in terms of providing a consistent instantaneous pace display and in terms of identifying running power zones. But if its use will spoil the running statistics, then I will rather stay only with the power of Garmin. If I were only running, I'd switch to Coros, which currently has full Stryd support. But I also swim and cycle, have a Garmin bike computer and a bunch of other gear, so it's easier for me to ditch Stryd

I am only running, so I actually looked a lot at Suunto Race S as an alternative.

I am not heavily into power based training. I tend to run pace based and then X-check against HR and power. But Stryd is great for instantaneous pace and the race prediction has been more accurate for me than Garmin. Still struggling with how to make best use of all the running metrics.

But one thing struck me. When I checked the watch, FTP it was set to auto detect and had picked up the threshold power from the higher Garmin values. So if that higher threshold is used with instantaneous power values from Stryd that will of course lead to a very low percentage of FTP, well below the recovery zone. I normally only look at power in Stryd PowerCenter so I have not really noticed this before. Still would not explain why high intensity runs seem to be overestimated.

I will enable Stryd pods again. Set Garmin FTP to Stryd Critical Power and try in another run tomorrow. Lets see if that makes any difference.

I am starting to wonder if Garmin is preparing some new physiological model to come out together with the next generation of FR watches. That could explain the many issues we have been seeing in the last version soo the software.

I always have the automatic detection of maximum heart rate, lactate heart rate and FTP functions enabled. Accordingly, for running it is now 367 watts, while the Critical Power of the Stryd is 275. At the same time, FTP for running was determined for me when the Garmin running power was disabled. Perhaps this disabling only affects the fact that the corresponding data is not displayed on the watch, but the data itself continues to be collected and analyzed by the watch. Perhaps the data from Stryd is also taken for analysis, perhaps this happens somehow arbitrarily and unsystematically. This has not happened before.

By the way, I have noticed that Garmin's race predictions have become more realistic lately. For me, they are almost identical to Stryd's predictions