400m Intervals - Inconsistent Anaerobic Training Effect

From what I have seen regarding training effect, it's nor linear.

Going from 0.0 to 1.0 takes much less effort than going from 3.8-4.0.

That looks to be the norm. I use a FR945 and did some intervals today and have similar results with a anaerobic TE of 2.7.

Mine wasn't as structured of a run as yours was. I tried to run .15 mi and rest .1 mi after about a .75 mi warm-up.

The Anaerobic TE algorithm looks at the RATE of HR increase. HR is a lagging indicator, and even in you don't reach LTHR in a short interval, if the HR spiked very quickly, the algorithm concludes it was an anaerobic effort.

In most of those intervals, the HR spiked very quickly, and you saw the appropriate TE. Except for the 1st 2 intervals. The first shows HR ramping up more gradually than the subsequent intervals -  With a more gradual ramp up, you were credited with a lower anaerobic TE. Perhaps it doesn't truly reflect the effort, but this is a pretty normal HR response to the first interval in a workout. You can see the same thing happening in Former Member interval workout also posted in this thread.

You also kept the pace high between the 1st and 2nd intervals, and HR didn't decline. So as you started the 2nd interval, your HR didnt have much to gain from the 1st recovery trough. 

The start to the 3rd (and subsequent) intervals shows a nice rapid climb in HR from a gentle recovery pace, and you got the appropriate TE. Each peak is slightly higher than the previous peak, which again is normal over the course of a workout.

In short, this is a pretty normal HR response from the workout you have done, and the TE seems in line with that.

Thanks for the comprehensive response, it makes sense.

How do you know the T.E. per interval, where can I see this data? 

There are real time Aerobic and Anaerobic TE datafields (under the HR datafields heading). I am assuming the OP just looked at their watch at the end of each interval. I don't think this is written to the .fit file per lap.

Thanks for clarifying. For me it still doesnt explain the Indoor cycling DSW I had today.  5min @135 1hr @200W, 15min @135W.  The estimated Anaerobic TE is 2.0.   My FTP is 240 and my LTHR is 156.  So basicly I only have one opportunity where my power and heart rate will increase which is after the warming up. From there on it is 200W constant but they will stay way below my FTP and LTHR. You could say that it is only one spike. But how could I ever reach an Anaerobic TE of 2.0 with only one spike?   And therefor form me it was no surprise that after the workout my Anaerobic TE was *0*  (zero).  So I am still confused how Garmin calculates the Anaerobic TE estimates for these kind of DSW's.

With an FTP of 240, I would expect to see zero Anaerobic TE from a steady state 200W interval. I suspect this is a labelling error.