Xert decreasing LTP and TP after a moderate (RPE4) but long group ride (200km)?

Quick question:
Why when I do my Sunday group rides at relative easy pace I see my LTP and TP drop several W? Why is Xert not “smart enough” to understand that an easy ride should not count as a real workout, without messing up the LTP/TP ? Is there a way to have Xert not counting the ride for LTP and TP calculation? Am I doing something wrong?

See below example:
(16) Xert - Activity | Difficult Polar Rouleur Ride (xertonline.com)

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What is your current status stars count or TL value?
When was your last BT?
What is your decay setting?

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I have 3 stars, LTP187 dropped to 173w and TP 238 to 235W.

I’ve been training to raise my LTP and succeeded to a certain extent. But once I do a normal ride, Xert kicks me down constantly, even if I’m, seriously much more fit.

Decay is set at Optimal/Defaut.

Same happened a couple of months ago while doing the virtual ride Espresso:

It seems that if you don’t push, constantly, Xert believes you losing fitness, which is far from being true.


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Hard to tell but looks like you had breakthroughs in those activities (?), and they came from sprint(ish) efforts, which increase PP and HIE. That can be offset by a slightly lower TP, but even if not, will reduce LTP (Xert now thinks you rely more on HIE at threshold so your lower aerobic power is less). You need to look at the whole power curve and all signature elements together to judge…

Your fitness signature will be reduced every day because of reduced training load. After each workout it will be adjusted up because of the training load. In summary, if you increase your training volume it will go up, if you decrease it will go down.

In addition, your signature might change if you have a breakthrough. That happens if you exceed the capabilities predicted my Xert. Furthermore, if you almost reach the max, Xert might adjust down your signature because it assumes you tried to set a do a breakthrough, but where not able.

Also note that the fitness signature has three parameters. A breakthrough can be that you increased the peak power, but reduced the other parameters…

Also. LTP will only be increased if you increase your TP or decrease your HIE…

My load is increasing and the drop is immediately after the workout. Doesn’t make any sense to me.

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These sprints are 2 sec effort after a red light catching up with my pals… after a 200km ride at most zone 2 . it’s not a real sustained effort “all out”. My LTP (real lactate threshold, tested) is well above 170s (tested for real).

I really don’t get how a easy/moderate ride gets converted to a difficult ride and downgrades your LTP lower after you demonstrated the opposite by riding 200km.

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I didn’t know that. Thanks for sharing this.
So is LTP a function of TP then.
If a person can hold 100w for 1br, then can hold a percent of that for 4-6hrs?

Appreciate you might not know, but a question for the hive mind?

Hey. Thanks for this … @wescaine

This is maybe helpful for my wider understanding.
Also seems to backup my ‘feeling’ that a lot of the numbers are based around peak power, which can have a wildly different relationship to threshold and 4-6hr power for different people.

Thanks for the explanation.

So from an algorithm point of view I’m not sure why a few sprints inside a 200km ride would result in a lower long term power.
Unless the execution of that ride just isn’t hard enough for Xert so it just assumes a decay in long term power irrespective of whether you do a 2, 4, or 12hr ride, if the LTP produced during it was less than signature?

@MilesAway thabjs for asking these questions - this is really interesting.

MPA, rather than PP. Peak Power is your 1 sec power at the top of the curve.

MPA™ – Maximal Power Available – Xert (baronbiosys.com)

LTP = TP - 2.5 x HIE

250 = 300 - 2.5 x 20

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Difficulty rating/score represents the highest difficulty achieved during a ride/workout.
In your example the majority of the ride ranged from Easy to Moderate but your MPA pull-down moments bumped the analysis results to Difficult Polar Rouleur.
If you highlight sections of the chart you’ll see a different focus duration calculated.

In particular the last 90 minutes of the ride looks like this –

Notice shaded difficulty portion of the chart rises to >75 (cusp from Moderate to Difficult score).

Easy	Less than 45
1.5		Easy	From 45 to 50
2		Moderate	From 50 to 62
2.5		Moderate	From 62 to 75
3		Difficult	From 75 to 90
3.5		Difficult	From 90 to 110
4		Tough	From 110 to 130
4.5		Tough	From 130 to 150
5		Hard	Greater than 150

The ride appears to be 10+ hours with lengthy stops.
You could flag the activity to block signature recalculation.

Thank you :+1::+1:

The sprints maybe short and you’re right that if it was a one-off effort, I would expect only PP to increase. But as you can see from the screenshots lasted by @ridgerider2 you were not recovering between those sprints, so you were also using some high (HIE) and low (TP) components. So the BT seems to have increased PP and HIE which lowers LTP.

I’d also not that if you had a BT after 200km (well done) it is highly likely you can do more when fresh. So if you want to really dial your signature you could do some hard efforts when fresher. You can also do some longer efforts which draw MPA down for longer, which will more likely result in TP and HIE adjustment only, and give a more robust LTP estimate.

Finally, LTP is not necessarily the same as lab tested values… partly because many labs have different definitions / turn points etc. I’m also not sure if you are referring to LT1 (first rise in lactate) or LT2 (threshold, but harder to see in practice) in your lab test, but sounds like the latter as you also refer to lactate threshold. Generally Xert LTP seems to be (a bit) above LT1 and Xert TP seems to be around LT2 or lactate threshold. If your lab LTP is LT2 it is to be expected to be well above Xert LTP and should closer to TP (assuming recent etc)

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Hopefully clear from @hpbieker but LTP is not actually a signature parameter (PP, HIE, TP), but the result of the formula he posted. There is no decay of LTP with duration (though apparently the next version of Xert will have that - different topic!). So it’s just that if sprints increase PP and HIE without changing TP, your LTP must go down.

LT1 is above Xert LTP and is the first rise in lactate < 2 mmol
LT2 is first rise above 2 mmol and is way above Xert TP for 20 min effort (which is expected since I don’t train or push for breakthroughs, so the signature is not updated).

My reflection was only on why LP decreases for a one effort of 2 secs with so many stops during the ride. The system should be able to see that those are too short efforts to be counted for a breakthrough and should not update the signature. This is why I’m not training anymore with Xert AI, I was being constantly being pushed down due to constant re adaptations of the LTP and TP .

If I follow Xert AI in a 1.5 month I would end up at LTP 180W… while I’m currently around 195-200W. In 1.5 month I’m likely to be at 220-30W inline with my current LT1 if I continue to follow my personal training plan.

Thank you , I flagged it.

I suggest you run one of the Xert Fitness tests to update your signature. It could very well be that your TP, HIE or PP is higher than you think.

I think if you are not working with an accurate signature, most of the value of Xert disappears… and it makes some sense that you are seeing some ‘strange’ breakthrough behaviour. If your signature was correct, the short efforts after 200km would not cause a BT (you would be tired and not able to exceed MPA most likely).

I will add that once your signature is updated, if you put it on no decay or slow decay, you will get the behaviour you expect i.e. your TP and LTP will actually go up after a long ride, due to the increase in training load. In my experience this works pretty well. But again, you need to fix your signature to start with

Agree with this. Just to add, would do them in slope mode (even the ones that say they are OK with ERG… it’s best to fully go to failure to express your signature naturally)

Yes, or at least modify them to allow for extended breakthroughs. If your signature is a bit off then you can easily complete the all out interval before you run out of steam.

Also note the importance of a correct PP.