Why threshold suggested workout have 1.0 of estimated anaerobic target ?

How quickly do you accelerate to the target pace? And does the workout consist of several threshold intervals, or just a single longer one. You mainly get anaerobic effect when you accelerate to a faster pace quicker than your hr can follow (forcing muscles to work more anaerobically for a moment).

Here is was one 18min segment@5:05min/km and i went from 6:30min/km to 5:05 almost instantly. But with that pace it doesn't require lot of effort.  

Piotr said:

My question is, why does Garmin estimate this anaerobic effect at 1.0

Because an effort at the "anaerobic" threshold is still mainly powered by the "aerobic" system. Of course, by definition, this is the point where multiple relationships have an inflection point (Speed vs HR, VCO2 vs VO2, Blood lactate concentration vs Speed, etc.), so the "anaerobic" system is sollicited. However, when the interval is completed. only a small proportion of it will not be covered by the pathway using your ventilation oxygen, and the EPOC will be essentially "aerobic".

For more info about the Anaerobic Threshold, there is a comprehensive read here:

https://www.ncbi.nlm.nih.gov/pmc/articles/PMC3438148/

Piotr said:

am I performing my threshold runs correctly?

The best way to execute them correctly is to perform a threshold test run (do not rely on the auto-detection) and to verify that the targets are matching the results of the test.

I would not worry about matching the expected Training Effect too much. If you curate your training data, have the HR Max spot on, then, with a balanced training, your EPOC evaluations, and therefore your Training Effect, will be accurate enough to ensure a decent match. Garmin's estimation of EPOC is HR-based which has a good correlation with actual EPOC. However, Garmin doesn't publish the std error rate fo the EPOC in %. From the data I saw, estimating from the R2 correlation factor, it is about 8%, which is pretty good (the VO2 Max std error is about 5%+)

https://assets.firstbeat.com/firstbeat/uploads/2015/10/white_paper_epoc.pdf

Piotr said:

Should I occasionally push myself a bit harder?

If the overall TE of the workout is "threshold", you are good to go for training purposes! If it is "tempo" or "VO2 Max" then the data is off. If it is "tempo" it could be because your threshold pace was too low or your recovery periods were still too intense (don't hesitate to wallk during those).

If it is VO2 Max, you were probably going too fast. If you are well trained, your capacity of using more of your VO2 Max capacity during "longer" efforts may be well developed and it is "easy" to exceed your threshold pace during these workouts.It is better to hover exactly around the threshold than to push your pace above.

Thank you very much for you answer and for the link. Interesting read indeed.