Threshold power and MPA

Hi all, I’m new to Xert currently in my third training week.

I have a question around my figures, especially I’m trying to understand my current MPA and the depletion under load.

I had a quite good training year in 2020 and I occasionally used The Sufferfest when there was no time for bigger rides outside.

I did the Full Frontal Test twice, one in May and one in October and improved ftp from around 250 to 290W.

However, if I look at the chart, I can see MPA decreasing for the two Max Power Intervalls (15 resp. 18min) and for the max 5min Power (at 23min), but at the 20min all out Intervall (32-52min) MPA is not changing at all.

Since this really was all out, for my understanding MPA should show a depletion to below my threshold power. But its not even decreasing by 5 points….

I wonder if at that time my signatures PP or HIE was calculated too high and what to to to adjust it?

Thanks for your replies!


To me it looks like your TP is too high.

You could open the activity, go to the advanced MPA tab and then lower at least your TP, maybe just to see what happens your PP and HIE as well, select refresh, then you should see blocks above MPA colored in yellow towards the end of your all out 20min intervall and finally select extract signature and see what Xert comes up with.
If you think it might be right you can save and lock the result, or discard and try again with other manually entered start values. As long as you don’t hit save nothing changes.

From the pattern (sprint, medium and long effort all in one activity) I would think Xert should be able to extract a resonably correct signature if it didn’t start too high as it apparently is.

Maybe there are better ideas from more experienced people or you could always ask support or look at the following help page:

I would venture to guess there is something off with your signature if you are not getting really close to a breakthrough in that workout. It is definitely one that should take you to your limits and that is what a breakthrough is.

If these were all out then your MPA graph line should be getting very close to your actual power output line, and really it should touch. My understanding is if your signature is correct then your full out hard efforts should be close to a breakthrough is all is perfect, as you get stronger then breakthroughs reflect that new fitness and therefore adjust your signature values.
Scott is really good at tweaking signatures that are not just right. There is a warning against resetting your signature because if you do not know what you are doing it will screw things up.

The alternative is to let you signature decay and do some full on hard efforts so that the system can zoom in on the right settings.

Just to offer a different perspective, breakthroughs are only meant to be possible when fresh, so to me it’s normal not to be able to ride above threshold (which is what’s required to bring down MPA; below or even at TP will not draw down MPA) for 20 minutes after the sprints and all-out 5 minute effort. Also, believe SUF is using that 20min as an estimate of FTP (hour power) while TP is typically a bit above that… and you weren’t that far below TP in that effort. You can check your 20 minute power (power curve) which is roughly what you’d need to hold to breakthrough for that time, and you’ll see it’s quite a bit above TP. Super tough when fatigued.

Also, if this is from October, hopefully you have some more recent BT efforts. The signature will reset itself so I wouldn’t be looking to make manual adjustments. For BT suggestions it’s worth searching the forum as there’s plenty of good advice :slightly_smiling_face:

Hey guys,
thanks for all the input.

I have been playing around a little bit and came to the conclusion that there is something wrong with the calculated ftp value. I should have realised that 1h FTP should be lower than mean power during the 20 min interval.

So I used to extract the mean power during the 10s, 5 & 20 minute interval and calculated the power curve from this to get tweaked MPA, HIE and TP. The result looks much better to me.

BTW, degression of MPA looks now similar to the ftp workout which can be found in the workout section.

I will continue training with this signature until I am able to go for a BT to reset my signature.
The last calculated BT was somewhere in November and I was not able to train properly between end of December and February due to illness. Now I’m in the base phase of the training program and last week I badly cut my finger so that I can only do endurance rides for the next 4-6 weeks on my trainer… :sob:

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Take note that using your MM( (mean maximal power) data can work okay for efforts like this that are performed at (relatively) the same intensity throughout until failure is reached. However, where you’ll start to see that method failing is with more complex patterns of fatigue, such as stochastic group ride (or race) data - check out this other thread: Xert Breakthrough TP vs Ramp Test discrepancy - #22 by ManofSteele

I would think this should be close enough to use as a starting point for your base phase. You might also think about switching to ‘no decay’ for the 6 weeks, otherwise your probably already slightly low signature decays further and your workouts might be too easy.
This signature might not be completely accurate and on the low side because all values are from one activity. Like Wesley said it’s probably not your very best 20min effort because you already did so much before that.

Wish you a speedy recovery for your finger.

I couldn’t resist. Taped the finger and participated in a crit race on Zwift. I had a BT at the final sprint and TP increased by 26 points to 276W.
I’m not sure if these 18min effort is representative, but as my LTP also increased to 206W I expect workouts to get too hard. I will check it tomorrow…

Check the usuals. Same power source. Calibrated. If it lelf-sided only, monitor more closely. If there are sharp stoppages in pedaling, especially at the end of BTs, be suspicious of the result. Some unfortunately can struggle with inconsistent data for a variety of reasons making it harder for them to accurately identify signatures.

If everthing checks and you still dispute it, flag it and see if it’s repeatable. If it’s repeatable, then so are interval targets. :slight_smile:

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A quick way to post a BT with signature changes in the future is to click on the BT badge icon and upload the report PNG.


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