I’m a bit confused about the workout I just completed. Bird: VO2 Max, 3x (5x 1/1).
It’s clearly labeled as a VO2 Max workout and I got a large boost on my VO2 Max progression chart (plus a small Anaerobic boost).
However, during the ride, the post interval result always showed “Anaerobic Capacity X/Y”. In the workout analysis all the intervals are labeled Anaerobic Capacity.
Why this discrepancy?
Yeah, they are conflating VO2max and anaerobic capacity a bit with these. Per the standard Coggan zones, zone 6 Anaerobic Capacity would start at 121% and VO2max would be 106-120%. However, Coggan later advocated for above threshold zones to be customized to the rider, using a proprietary method (WKO iLevels).
Another way to look at it (and my assumption about how WKO determines iLevels) is based on the time frame of interest. Coggan also defined time durations that an athlete should be able to manually last (TTE) in each zone. VO2max TTE is 3-8 minutes, AC is 0.5-3 minutes.
You can look at your PD curve to see what %FTP is sustainable for you for that amount of time and reduce it by 10% or so to account for the fact that you’re doing multiple intervals. That was suggested by Kolie Moore as a method to ballpark appropriate intervals.
In general, TR blurs the lines between zones at the upper PLs. For example, Pap is a Tempo 10.5 but it’s essentially Sweet Spot given that it’s 82 minutes between 87-89% FTP.
I wouldn’t sweat it too much though. Aside from LT2 and Pmax, our bodies don’t really have distinct zones, it’s a spectrum. Training VO2max and AC will have very similar effects.
Thanks for the very thorough reply. Most of it is above my knowledge in this subject, but I get the gist. I’m going to trust the process and not sweat it too much.
(although, I still don’t get why the software calls it VO2 Max workout and calls the intervals AC. I’ll just ignore that and continue the suffer fest 
)
The small Anaerobic boost in this case would be a boost in a secondary Progression Level 
In some cases, workouts will have you riding in multiple complementary power zones. For these, you may also see a Secondary Progression here displaying the additional changes to your Progression Levels.
Bird is on/offs, which means they use a series of shorter higher intensity intervals to stimulate more time at VO2 max (which is the state of maximum oxygen uptake, which is slightly different to a power zone…). If you did the on parts in the power zone defined as VO2 max (106-121% I think it is in TR), you’d never reach that state with intervals that short - that power zone will only get you to max oxygen uptake if you keep going for a longer duration (i.e., 1 minute at 110% is not going to get you to that state of maximum oxygen uptake, even if the power zone is called “VO2 max”).
If you look at other on/off VO2 workouts you will see the same thing.
I don’t know if I worded that very well, but what I am trying to say is they use lots of sets of short intervals at a higher intensity to try and get you in that state of max O2 uptake for longer than would be possible for VO2 long intervals.
Yeah, I’ve posted this before, but it seems to be a frequent source of confusion that we have both power zone AND oxygen uptake workouts that are called “VO2”. Often, just being in that power zone isn’t enough to significantly impact the oxygen uptake. This isn’t a TR issue, but it is a regular source of misunderstanding in the training world and I think it’s important to clarify whether your workout goal is to spend time in the power zone or to maximize oxygen uptake.
I see. That’s a very succinct way to put it. The only thing I’m not sure about is my workout goal. I’ve been letting TR plan building do that.
I’m currently building fitness back up after an extended hiatus. So, I’m in the middle of very rapid improvements as my body comes out of amnesia.
When I did Bird, which was listed as vo2 max level 5.5 (from my previous 3.4), I didn’t ever doubt I would finish it and didn’t really “feel the burn” until the last set. I wonder if it would be a good idea for me to pick an alternate vo2 max workout next week, with longer intervals. It’s scheduled for a 6.8, another huge jump, which seems to indicate that the AI is still a ways off from knowing what I can do. (according to Garmin vo2 max estimates my vo2 max has gone up 32% in three months). I’m thinking maybe bump it up to something with 2 minute intervals, around 6.0. Does that make sense?
This is EXACTLY the confusion I was referring to. Garmin telling you your VO2 Max is improving is them looking at your heart rate.
TR prescribing a VO2 Max workout is looking at power output. I don’t mean to imply TR aren’t aware of (or don’t use) the HR data, but the last time I remember discussing this topic, @Caro.Gomez-Villafane gave this answer (click to see her whole reply for the relevant part):
BTW: That’s a pretty interesting (and short) thread, if you have time to read the whole thing.
Thank you! I read the thread you recommended and it was very helpful.