How to setup auto detect heartrate and lactate treshold?

The HR auto detection probably takes into account past runs (who knows?!) so lowering it manually might be a good way to allow for another round of estimation. But then poisonous data from the past will still throw it off, I guess.

I'd still recommend you do an HR Max test, if your doctor lets you. One way is to do a committed anaerobic or VO2 Max interval workout and add last maximum-steady-effort intervals of the same length as the previous ones until exhaustion at the end.

How do you do an "easy" run and get a new max HR of 194? Either the run wasn't easy or your max is substantially higher. 

LinAlan said:

How do you do an "easy" run and get a new max HR of 194?

My thinking exactly. One explanation could be that false peak data was part of the easy run (dry chest strap, etc.). Another is that the watch is considering historical data to validate/propose/predict a new HR Max (I don't think it is the case).

I didn't find any publication detailing how the HR Max algorithm works in details on Garmin watches, but for another tool, Firsbeat recommends that users double check in their training data that there is a valid segment at the proposed HR Max.

The following excerpt is about another Firstbeat software tool, but I suspect it is the same or similar on the watch, emphasis added.

"The program calculates the default maximum heart rate with the following formula

210 – (0.65 x age) = maxHR

If the analysis finds a higher value from the measurement period than what the formula provides, the program notifies that the newly found maximum heart rate is updated to the background information. If the program suggests, for example, a max heart rate of 220, it is a good idea to visually inspect the data and make sure that the value was found from a reliable data segment (and not e.g. from an error peak). This can be easily checked from Lifestyle Assessment from the Measurements view."
https://support.firstbeat.com/hc/en-us/articles/360015387173-How-is-the-maximum-heart-rate-in-background-information-determined-

Yes, my run was suggested as easy, 36minutes@6:15/km. Very easy for me, although it was pretty warm.

The 'algorithm' is very basic. It uses the age-based formula bit if you reach a higher value in a workout then it sets this value as your new maxHR.

It is always best to test your maxHR in a field test

And how do you explain my situation then? It gives me max heart rate of 194 after an easy run, with max 156 and average 146 bpm. So well below the age-base formula (177,5), but still max heart rate adjusted to 194.

Today I had my first lactate treshold test. It went fine. As two weeks ago, I set the lactate treshold to 150 manually. After the test today, it was set to 158. Accepted on the watch and synced with GC. Curious what it will do to my training intensity, because I think Garmin is still keeping it very easy for me.

There was an 'official' bug reported about this. Not sure it was also fixed

DaKo said:

Do I need to use ANT+ or BT connection? With BT connection, I am probably not able to use the music player with by BT earbuds right?

Doesn't matter. You will be able to use your earbuds any way. Note that the downside of BT for the HRM pro is that you might have difficulty connecting both to the watch and your phone. Whenever I used BT for the HRM pro and it was set up on the phone, I had to forget the device on the phone to be able to connect to the watch. I am using Ant+ all the time now.

DaKo said:

Do I need to run with the strap forever? Or just to do the test, and the intensive trainings like treshold runs? And if I do run without strap, but with wrist based HR, how does that interfere with the automatic update?

Always recommended to use a chest strap. You can get wild readings with wrist HR so if you care about the accuracy of your HR metrics, keep using a chest strap.

DaKo said:

There is no faulty peak in the data, my run yesterday shows max heart rate of 156, and average of 146.

DaKo said:

Today I had my first lactate treshold test. It went fine. As two weeks ago, I set the lactate treshold to 150 manually. After the test today, it was set to 158. Accepted on the watch and synced with GC

With a threshold at 158bpm, your easy run was at 92% of threshold (average of 146), I would expect more like 75% of threshold for easy. So something is not quite right about your metrics. Also note that for most, but not all, people, threshold is around 90% of HR Max. That would put your HR Max at 158/0.9=176bpm.