I read that blog post years ago, skipping to the end it states:
- 0–3.5 percent: The workout was within your aerobic intensity zones, but you should do the test again at a starting heart rate that is 5 beats per minute (bpm) higher.
So they suggest ratcheting up to a higher heart rate on subsequent test. Over time I’ve done it at a wide variety of durations and power, just a few examples:
- 3 hours at .73 IF (140bpm)
- 2 hours at .79 IF / 1.02 VI with 0.05% decoupling and then I ran out of road and water on a hot day (148bpm)
- ~1 hour at 1.00 IF / 1.00 VI with <3.5% decoupling and HRavg just below lactate threshold HR (156bpm)
Those were outside, I’ve done them inside as well. At least for me, its not the best functional measure of my aerobic fitness. Not sure what going a lot longer would accomplish, perhaps it would be interesting if I was doing full distance triathlon.
Here is a 50+ minute (51:33) threshold effort outside, about 10 days after a 20-min field test that bumped up my FTP:
That last one has 1.005 variability index and decoupling of 3.1% at a temp of 68F. Honestly I don’t think its misleading or wrong, or that I should reject the result and go inside to “clamp power” using Erg.
It is after all a Functional measure of aerobic fitness.