Brasstown - Stretch Workout?

My plan has Brasstown scheduled for tomorrow. This is also a Recovery week. I find it interesting that Brasstown is classified as a “stretch” workout under Endurance 5.2. Leading up to this I’ve done plenty of 1:30:00 rides that were considerably harder than Brasstown, and were all classified as “Productive”, albeit those were “Threshold” workouts. I might be inclined to think that Brasstown is classified as “Stretch” because the Plan hasn’t assigned me any Endurance rides until now, so my Progression Level is pretty low under Endurance; however, even the last Threshold ride I did was classified as Productive, even though it was +.4 greater than my current Progression Level under Threshold. Is the reason Brasstown classified as Stretch because of my current Endurance Progression level? I have no doubt I can complete this ride with a final report of “Easy”, but why would TR assign a Stretch workout during a Recovery Week?

  • Yes. The Difficult Level is a direct comparison between your Progression Level and the related Workout Level in all cases.

  • I need to search to find if there are hard values for each of the steps, but here is the basic article that covers the Difficulty Levels.

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After some research, here is some data on the steps based upon a couple of my current PL’s:

Sprint PL = 1.0

  • Achievable = 1.0
  • Productive = 1.1 to 2.0 = (0.9 delta)
  • Stretch = 2.1 to 3.5 = (1.4 delta)
  • Breakthrough = 3.6 to 5.5 = (1.9 delta)

Anaerobic PL = 3.9

  • Achievable = 1.0 to 3.9 = (1.0 to current PL delta)
  • Productive = 4.0 to 4.9 = (0.9 delta)
  • Stretch = 5.0 to 6.4 = (1.4 delta)
  • Breakthrough = 6.5 to 8.4 = (1.9 delta)

Endurance PL = 7.6

  • Achievable = 1.0 to 7.6 = (1.0 to current PL delta)
  • Productive = 7.7 to 8.6 = (0.9 delta)
  • Stretch = 8.7 to 10.1 = (1.4 delta)
  • Breakthrough = 10.2 to 12.1 = (1.9 delta)

I got these values by using the TR Android App, loading a workout in that zone, then using Alternates and looking at the Difficulty options. It list the actual ranges shared above for any workout relative to that zone.

There are some general trends to see but I wouldn’t be surprised if zones had different steps between the Difficulty Levels, not to mention it might be relative to your PL at that moment. Hard to say more with such a small capture of data, but it gets the general trend at least.


In my view, TR have a very poor implementation in AT of how levels in one zone affect levels in another. My hypothesis like yours is that 99% of those that can do level 5 (say) threshold can do endurance at that same level, especially for the same overall duration workout (it might not be true for say a 4 hour endurance ride). This does not translate the other way though (i.e. if you can do level 5 endurance it wont mean you can do level 5 threshold). I also dont think it necessarily translates for higher than threshold, for example if you are level 5 V02 max, not sure it implies level 5 threshold will be achievable with a high probability.

Edit: yes it is assigning it as stretch because your levels are low. However as per above it makes no semse that your levels are classed as low simply because you have not done endurance classified rides.

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I guess I can be grateful that the Plan didn’t try to assign me a Productive Endurance ride, which would have bee waaayyyy too easy. Probably 1.5 hours of 55% FTP.

I am purely guessing here, but the fact that you got a Breakthrough assigned may actually be a sign that AT IS actually looking deeper than the pure PL and WOL values. It likely depends on the zone in question, but it may well have served you a BT instead of Prod workout BECAUSE of your PL in one or more other zones.

We don’t have that info, and there may be a good reason TR is not making that selection more transparent. Or it could be a bug too. We just don’t know.

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Maybe but in reality it would not be “breakthrough,” . Its achievable for (>95%) of people in this situation so why not just adjust the model’s level correlations to more accurately calibrate where the person is estimated to be at and so that the workout rating is correct?

If i remember correctly there were no correlations between levels allowed for when At first released then they made some adjustments after ibthinkbfor levels in closer physiological proximity. So i suspect it just wasn’t thought through properly…

Perhaps part of the problem is that Endurance “levels” is actually primarly about durations that exceed typical TR workout times in plans (its not as much about intensity that you can hold for 60-90 minutes comfortably).

  • Yes, purely within the definitions TR has created with that set of levels I shared above. It is the simple PL vs WOL value, nothing more… nothing less.

  • What “makes sense” in a broader view is something that requires more discussion with TR specifically.

  • Great question, and one that only TR can answer.

I think of these as difficulty based on energy system. You might be able to it but at an effort/heart rate level greater than that work out is intended to produce. Finishing Brasstown at 160HR is different than finishing the same watts at 120 HR. So in some ways, I see these as breakthrough workouts when I can finish them at record low heart rate/breath/efforts, rather than just being able to finish it. Its a great day (especially as a triathlete) when I can do a 240w workout for 1-1.5 hours at under 120 HR