Im a flatlander settling in Copper mountain (9600ft), acclimating for the leadville 100. I was going to do my structured workout tomorrow, and wanted to adjust the power targets down by 20pct to account to account for the power loss at elevation. When I changed my 340ftp to 272, I just got a workout with insane progression levels, not the intended one. Is there a way to adjust? Or am I better off just riding on my own by feel from now on?
As far as I know, the TR system does not have a mechanism to select appropriate workouts when you are significantly changing altitude. It has an idea of how many watts you can do based on your history, but I’m not aware of a way to reset that besides manually adjusting down the intensity of the prescribed workout after it’s been prescribed. I’m up in Leadville now and adjusted my ftp down by 18%, mainly just to keep tabs on tss and time in zone. Any intervals I’m doing, I’m manually picking appropriate wattage and duration. Changing ftp in the system and letting it pick workouts will not adjust the difficulty of the workouts down, the system will just try to find an appropriately hard workout (for your normal altitude) by bumping up progression.
Yeah thats what im seeing. Im thinking of writing the workouts down at 340, then lower the ftp, and just load them manually
Yeah, in this case, it might not make a ton of sense to adjust your FTP so significantly. As you’ve already discovered, you’ll just get higher-level workouts.
Keeping your FTP where it was and then scaling the prescribed workouts based on RPE is likely a good option. 
I would not adjust in TR. Just take your wattage targets and multiply by .8 as a starting point, then adjust by feel / RPE.
How do you “write the workouts down”?
“How do you scale the prescribed workouts”? Like, which parameters do you do/change?
Multiply FTP by .8, then use same wattage target by percent.
If it’s 90% of FTP, then it’s still 90%, just of a lower number
Okay, but I’m wondering, once you have the target number, do you just go for that number during the interval, or do you make some parameter adjustment in the trainer road app/workout so you are still following some prescribed workout?
No, ignore the levels in the TR workout. No adjustments other than above
With a pen and paper.
In all seriousness thats exactly what I was proposing to do tho. Write the name of the workout down at sea level altitude ftp. Then adjust the ftp in the app, which will result in TR AI giving you new high progression workouts. Then you replace these workouts with the one you wrote down, and voila, you have the workouts scaled.
The above advice is good if you want to scale to a specific number. You don’t have to do anything serious in that case.
My suggestion was to use RPE as a factor as well. Altitude affects each of us a little differently, so starting with your workouts at 80% of what they were before could be a good place to start, but allow yourself to fine-tune things when you’re out on the road. You might need to go even lower at first, or maybe you can do more power at altitude than others. 