So, Tuesday I had on my schedule “Snowshoe Fire” which is categorized as a VO2 Max workout. In simple terms, it has 4 X 5:00 intervals at 105% FTP. A total workout of 90 minutes.
Today I have Mansfield +3 which is 7 X 5:00 intervals at 105% FTP and it is categorized as Threshold, also a 90 minute workout.
I’m confused, same power targets, same interval duration, different zone designations (number of intervals not withstanding). Enlighten me, please.
Gerry
It " could " be because the 7 x5min intervals add up to a total of 35 minutes in zone.
Where your first workout which was 4 x5min add up to a total of 20 minutes in zone.
Typically anything pushing into 30 minutes plus in zone would take you out of the VO2 zone and be considered more in the line of threshold, even if the work intervals are only 5 minutes long which sounds short when thinking of threshold but doing enough of them would get you over 30 minutes of zone time.
If you can accomplish the 7 x5 minutes in zone, it could potentially mean you’re going in the right direction as far as fitness is concerned which is a good thing.
Snowshoe work out is 106% the other ones 105%
Numerical values were same…
The zone analysis you are making is backwards, it seems. As VO2 Max would be considered greater effort / power output, the longer work load would equate to VO2 Max, not threshold (lower zone) in your scenario. But I understand how you were thinking.
For me, it shows a 2-watt difference between the interval power targets.
I think I explained it right?? But to add to it, I see Mansfield is listed right at 105% which is top end of threshold and Snow shoe fire is listed at 106% which is theoretically VO2.
I’ll stand by my time in zone explanation but a more accurate answer is simply the workout stating a 105% for threshold compared to a 106% for VO2.
zones are an artificial construct, and you are dealing with two workouts on the border between two zones. From what I read so far (one is 105% and the other is 106%), just ignore it and go with whatever TR assigns.
I disagree. The two watts push it entirely into VO2 and is no longer threshold 
But on a serious note, if you nail 7 intervals that are effectively the same, that could inform picking a harder VO2 workout in future planning so your workout levels match more appropriately. 7x5 @ 105 is gnarly. But maybe 4x5 at 110 or 112 would be more appropriate for a VO2 stimulus, or pick billats or hard starts. Whatever addresses your fitness goals better
Maybe @IvyAudrain can explain but agree seems weird. To be honest…in my view anything under 110% is v unlikely to be v02 unless quite long (10-15 mins) durations.
Hey Gerry! Thanks for the question. @RobertSims this one is for you too 
Snowshoe Fire is categorized as a VO2 workout as it is at 106% of FTP. This is the percentage at which our workouts at the lower end of VO2 Max begin – and those lower percentages are often paired with longer interval durations to really focus on building sustained power.
Mansfield +3 is categorized as a Threshold workout since its intervals are at 105% of FTP. This is what we would categorize as “suprathreshold,” or just above threshold while not quite breaking into full-on VO2 Max.
Additionally, while power zones do overlap with one another, especially at very close intensities, the distinction between zones does have to be made at a certain percentage of FTP so we can categorize workouts appropriately.
Hopefully this helps clear things up! Let us know if you have any other questions 
I’m not new to training with power, or TrainerRoad for that matter. Perhaps my question could have been better worded. It makes little sense to have two nearly identical workouts, such as these, only two days apart. If there is to be a VO2 Max workout scheduled, give me 110%, truly in VO2 Max zone. Seems redundant to have it scheduled as such, particularly when the acceptable variance for workout can be up/down a few watts and both be considered successful. Just my thoughts on the schedule lay out / work out structure.
Maybe this is an odd interplay of adaptive training with a workout plan? If your Vo2 zone is 4.8 (snowshoe fire) and threshold is 3.9 (Mansfield+3), those similar workouts could have nuanced adaptations simply because you have much longer rest in the vo2 workout.
Using workout alternates to push the threshold workout to 4.9 the work time bumps up and the rest intervals get much shorter, resembling more of an threshold endurance workout.
There’s a lot going on in the trainerroad software to account for the “bell curve” of cyclists and while we can probably set it and forget it, I’d recommend to take the plan with a grain of salt at times and use an alternate to get what you’re looking for.
The intensities and durations of the intervals in each of these workouts in question are indeed close. That said, this is an instance when your Progression Levels for VO2 Max and Threshold (combined with the type of plan you’re on) happen to align in such a way that you get two similar workouts.
While the workouts are similar, both will be beneficial in building the fitness you’re looking for with the plan you’re on. As you progress through your plan, Adaptive Training will move you forward independently in each zone, continuing to dial you in with workouts that will increase your abilities in VO2 Max and Threshold.
Additionally, as @odpaul7 mentioned, you can always use Workout Alternates to find a different format for the workout you’re looking to do!