This likely has been answered in other posts but I could not find it so apologies if this is redundant.
My issue is that I fail at longer sustained intervals, for instance 2x20 at 90%, but don’t have an issue with short or medium punchier workouts. Of course my goal is to train at the right intensities for all workout but whenever I see a long sustained interval workout I am skipping them because I know I am going to fail. : (
My current Fitness Signature is:
PP - 972
HIE - 21.4
TP - 250
For reference my Strava power curve shows my best hour power in 2025 was 220. I know TP is not exactly the same as FTP but if I look at the “It Takes 2 - 90%” workout it is using 90% of my TP. So if my FTP is really 220 or 225, not 250, then I am working out at my threshold or slightly above and this would explain why I am failing on the longer sustained intervals. Also if it is using TP to set power for other workouts I may be working out at Zone 3 instead of the intended Zone 2 or the like.
Are you POSITIVE? Did you actually use your outdoor power meter indoors on the trainer doing the same workout to compare? It’s easy to overlook this if you just did a casual test by looking at a display in Zwift or Xert EBC while pedaling. You need to actually compare the real data output from each.
If you did this, and they agree, then apparently I’m the only one with power meters that disagree but I wouldn’t have known without testing. Judging by just casually looking at the numbers in real time in an app, I initially thought they were close enough, but it turns out they are off 8% at TP and probably 20% at PP!
Of course if you use the same power meter to control the trainer, this is definitely not the problem but it could be if you only just started doing that (could be a problem in your older data, before using a single PM, which developed your Fitness Signature).
Not 100% sure since they are different power meters (Wahoo Kickr Bike indoors and Favero Assioma outdoors). Here are the key numbers for inside vs outside for the last year. They track about like I would expect. I ride indoors about 4 times as much as outside. Most of my breakthroughs come from outside group rides though.
I had exactly the same issue until recently. My TTE was pitiful but I could smash out 450-700 watts for up to a minute no problem. I even googled how to increase TTE but was still getting wasted on Threshold/VO2 type efforts. So I ran aggressive decay from my last breakthrough and for a month and that sorted things out. XERT dropped my TP by 30 watts, though humbling and not something I wanted to see, everything suddenly lined up. Breakthroughs apart from repeated peak intensity efforts are happening. So my TTE wasn’t wrong, but my threshold was. So if you have signature decay set at none or small, give it a go.
You can revert back if you don’t like the changes.
To do that change decay back to original setting and recalculate.
If you don’t see a significant drop, there are other options to explore.
How many BTs in the last 90 days? (XPMC set to 3 months)
My next suggestion would be riding a couple over/under workouts and see how they feel RPE-wise.
On your next HIT day try this TP o/u: Until the End - 3x16
On your next LIT days try this LTP o/u: Save Yourself - 75
What % do you need to lower intensity to before these over/under workouts feel about right?
I’m not time-crunched and I don’t like to grind much so I will avoid selecting any traditional straight block sweetspot intervals like It Takes 2 - 90%.
I do select workouts that pass through tempo/SS but not hang there for too long.
Are you time-crunched and prefer SST as integral to your training?
Do you do fine on punchy HIT workouts with your current signature?
I will try those out and see what they feel like. My guess based on what I know of myself is I would struggle to get done with “Until the End” at my current TP. My guess is that I would just make it through the second major set.
I dont have trouble completing punchy HIT workouts. Earlier in the year my TP bumped up to 268 after a breakthrough and I was still able to complete all workouts except those that required sustained threshold, or even within 80-85% of threshold.
FWIW, I get much better recommendations from Xert when I only use the Availability to specify a Rest Day, not any particular times on actual workout days. Whenever I do the latter, it seems to generate more confusion than useful results. YMMV I suppose as this depends on so many things. Just my experience.
Seriously consider the power meter accuracy issue, especially if you train indoors for a block (like winter, duh?) using one power meter, then outdoors using a different power meter for the rest of the time (I think this is most people, by far). Consider that your Fitness Signature is set by your outdoor PM and imagine what happens to your indoor training as a result. You can waste a lot of time and workout energy if they aren’t closely matched!
My goal there is obviously just to let Xert know how much time I have to train that day so it doesn’t suggest a 2 hour ride when I cant do that. The time of day is set to “Use Advisor”. My day off is often necessitated by work and life and therefore changes week to week so I don’t specify it. Not sure if this is better or worse that what you suggest.
Since my outdoor bike has a pedal power meter I may try swapping them onto my Wahoo Kickr Bike and see how closely they track at some point.
Yeah, I’ve tried using the Availability that way for similar reasons - obviously that’s what it’s designed for! I just found Xert works best for me personally when I give it more freedom (doesn’t everyhing?)! The fewer constraints the better IME. Of course, we don’t all have that luxury so I definitely get it.
Don’t forget that if you do “free” Xert in this manner, it still provides a long list of Recommended Workouts so you can pick and choose whatever works best for you that day. I actually think this is where the real unique and powerful part of Xert lies - structured freedom? Anyway, it’s FAR more flexible than most other platforms at the very least. FWIW, I don’t think other platforms have the underlying training philosophy and metrics needed to pull this off.
Pedal PMs are really good in that respect - easy to compare. I have never owned pedal based PM but have read that it’s important to using a torque wrench and remember to Calibrate (zero offset) when installing to get consistent power data. Maybe you’ll also find you can calibrate (slope) your pedals to match your trainer PM after you compare the results.
PS. My 1% and 1.5% claimed accuracy PMs were actually 7.5% off (in slope). Imagine trying to do VO2 intervals indoors on the lower reading PM using a Fitness Signature built outdoors on the higher reading PM! Not going to be possible for most people.
so I will avoid selecting any traditional straight block sweetspot intervals like 