Anaerobic? Nope.

4964205 said:

Why I think that, you may ask. Well, it's because 20 days ago I did a long cycling activity which was really easy but it got qualified as mainly anaerobic

The big difference is that the running and cycling activities do use pace and power to improve the quantification of anaerobic EPOC. 

For other activities, the only information used are HR dynamics. The watch is looking for rate of change of HR and repetition patterns in this case. For example, traditional strength training is almost 100% anaerobic, but no way for the watch to measure it through HR dynamics. Same thing for rock climbing, etc.

I am not a swimmer, but I was hoping that the criticial swim speed would be used to help identify anaerobic efforts, but apparently it isn't used?

https://support.garmin.com/en-US/?faq=h56ydwZxU8A7oi2OSh0y66

Question: how did you get a 2.3 anaerobic effect in an easy long bike ride? Just curious.

Etupes25 said:

Question: how did you get a 2.3 anaerobic effect in an easy long bike ride? Just curious.

Probably in much the same way as I did with a few incline sprints along the way.

Yeah, I was surprised by that too. It was more of a social event than a sports activity. It comprised of something-teen stations around the city with open air tasks and quiz-like questions. From station to station we were moving on bikes. It was a lot of fun, easy-going, it took almost 5 hours and apparently it was the biggest anaerobic activity I have done in my Garmin life :-)

Anyway, that and my interval swimming mean one thing to me: you have to take Garmin activity assessments and recommendations with a big pinch (or spoon) of salt. They have tracking acuracy disclaimers on their website as well as in the app. Being Garmin fan I want my Fenix 7to be my daily guide and sports oracle but it is not. Keep that in mind and "listen to your body" :-)

If possible you could try with longer interval to see if it has any effect. Even though you feel you are maxing out already from the beginning of each interval there is such thing as cardiac delay. It takes time for the heart to catch up with the output effort. Im a runner and i know its in a whole other ballpark, but if i do 200sprints my heart rate dosent catch up and i end up doing zone 3 training = no anaerobic effect but if i do 400m, oh man its another story 

mcbit said:

Probably in much the same way as I did with a few incline sprints along the way.

Yes, that would do it. I can see your time in power zone 7. I get this on long easy rides when I do "hard" starts at the light also. 

4964205 said:

Yeah, I was surprised by that too. It was more of a social event than a sports activity. It comprised of something-teen stations around the city with open air tasks and quiz-like questions

It is always hard to rationalize the results of the Garmin metrics, since there is little public documentation and the FirstBeat technology is a black box.

We can see that your heart rate was in zone 5 for a few seconds. That suggests that some HR peak periods were reported to the watch.

This high HR periods could be real or some aberrations from the wrist HR or even a chest strap). Maybe the pattern matched a repetition one that had the watch give you points for anaerobic EPOC.

entify said:

If possible you could try with longer interval to see if it has any effect.

That is a good suggestion, but remember running is helped by pace information. What I found is important also is to have long true recovery periods. For example if you do hard 1mn sprints with 30s walk or jog intervals, you will likely get tempo rating (but you will have anaerobic effect). However, if you run hard 1mn and jog for 2mn, you might still get overall tempo rating because the HR doesn't drop fast enough or your jog is a bit too fast. I found that walking at least at the beginning of the rest interval makes a bit difference.

Now this is all about getting the watch to reflect the intent, either form of training 1mn/30s or 1mn/2mn is a good one.

I guess a lot depends on the information recorded. If you look at my data above, my heart rate highest value is in Z3 but it probably only goes above Z2 on 2 occasions during the entire ride. The power data makes it clear that there are anaerobic efforts but if analysed without the power data I think the interpretation might be quite different.

Same issue here with Pool Swimming activities.

All my sprint workouts (for example 10x100 + 10x50) have anaerobic value of about 2.1  and always lower then aerobic...

The main benefit always target as "tempo", not "sprint".