More Garmin Connect weirdness: Training Effect numbers

Can anyone suggest why Garmin says my last ride (an FTP test) showed a Training Effect of 0.1 when I spent over 18 minutes in Zone 5?

Am I misunderstanding what anaerobic is?

I presumed anytime where HR is in Zone 5 is classed as anaerobic….

No. I’m not sure exactly how it calculates this but I’ve noticed that what seems to matter is not so much how long you spend at a high heart rate but how quickly your heart rate changes. I can do a run where my heart rate is as high as I can maintain for most of the run and it still gives a low anaerobic effect. But if I do a run that is mostly gentle with a number of very short (say 30s) flat-out sprints with a decent amount of recovery (to allow the heart rate to go back to a low value) that can give a much higher anaerobic training effect.

You have to do intervals to get a decent anerobic training effect score. Don’t know if this reflects reality when it comes to improving fitness.

Realistically would you expect a single FTP test to have much of a training impact? I wouldn’t, so I guess Garmin is probably not far off. They use Firstbeat algorithms and you may find more information on the Firstbeat site, not Garmin’s.

How have you determined your heart zones and do you evaluate them every 6-8 weeks, to account for fitness changes, just like power zones?

Strava’s automatic algorithm, based on your observed max heart rate, used to give me very different zones compared to https://intervals.icu/ using 98% of your highest 20min average to estimate my Lactate Threshold Heart Rate.

From my experience, a ramp test like the one on Zwift (20W target increase every minute, starting at 100W iirc) will create far less fatigue than a more traditional 20min FTP test.

My understanding is Anaerobic is not using oxygen to produce power, ie short sprints you can’t keep up for more than say 5 so seconds. So a session that has a duration of minutes isn’t training that muscle energy system especially.

Zone 5 is your max aerobic zone. Need to dip into power zone 6 and 7, ie beyond vo2 max, to be anaerobic.

It say’s Indoor Cycling. It doesn’t count you know ! LOL.

My understanding is Anaerobic is not using oxygen to produce power, ie short sprints you can’t keep up for more than say 5 so seconds.

Its anything up to a minute or so (the problem is burning glucose without oxygen produces a bunch of byproducts especially lactic acid and once it gets too high you crash out).
Definitely something like that graph shows isnt anaerobic.

Garmin give a rough guide of how activities map across.
Even more roughly sprints/intervals == anaerobic and anything else aerobic.

For op your max heart zone definitely seems to low.
Zone 5 should be impossible to keep up for more than a few minutes.

Garmin give a rough guide of how activities map across.

Even more roughly sprints/intervals == anaerobic and anything else aerobic.

Ah, ok. That Garmin explanation covers it and I was wrong to just assume Z5 = anaerobic. That session wasn’t intended to be targeting anaerobic but I was kinda surprised it barely registered…

For op your max heart zone definitely seems to low.

Zone 5 should be impossible to keep up for more than a few minutes

I’m 60. My heart ain’t going any faster than the final push at the end of an FTP session (and I’m more of a big diesel than a Ferrari)