Xert and intervals.icu estimated FTP way higher than ramp test. Is that normal?

I’ve been using intervals.icu for a while and it has a lot of awesome features, huge fan. But I notice the estimated FTP seems high. And I started using Xert (trial) while waiting for AT here and again, it’s estimated FTP is way higher than what I’m getting with TR. Is there a setting I need to change to get a more accurate FTP? My thought is that my power curve skews the FTP calculation somehow.

I can’t count how many times I’ve read on this forum that the ramp test overestimates FTP, so it struck me that both Xert and intervals.icu are giving me a much higher number.

Ramp test FTP: 314
Intervals.icu: 335
Xert: 342

Same bike, same PM (Assioma Duo). Can I just suffer more outdoors as that’s the only thing different. I’m not new to the ramp test and can bury myself to the point I’m falling off my bike and have to lay on the ground for 5 minutes or so before I can do the cool down.

The reason I’m curious is that the weather is getting nicer and I want to do outdoor workouts, so it would be affecting the power targets I go for. If I’m able to hit higher numbers outdoors, should I adjust my targets accordingly? Or use the ramp test indoor FTP? Or am I overthinking this?

Post your power curve and we can help you

The Xert one has way less data points since it’s the trial, so that could be a big factor.

My 5 min power test usually overestimate my FTP by 10W in intervals. My record overestimation from xert was 15W. This is why any short (ramp test included) effort is only estimation of FTP. The only way that works for me is ride for 40-60 min at threshold and then you know your FTP. The other thing is the more you ride near your FTP you feel if it is lower or higher.

WKO mFTP if PDC is filled ok’ish is usually spot on.


Yea, I haven’t done any long sustained efforts for a while. I mostly race CX and now some crits. I was doing longer and longer SS intervals back in Nov-Jan, and got up to 1x55min @90%. But since then, I’ve been shortening the duration and going for higher power as the crit season is starting up. More anaerobic and VO2 stuff. Longest SS or threshold interval in the last month or so I’ve done is maybe 15 min.

Somewhere in the 310-320 range seems right but it looks like you haven’t given it a good solid effort in the 30-40 minute range so it’s tough to say exactly.

It’s definitely not 335

TTE is probably low but given your training focus recently that wouldn’t be surprising.


Agree with @stevemz - hard effort 30-40 minutes would be helpful but your ramp test estimation seems closest to the truth.

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That’s quite a difference but for the majority of people outdoors is higher than indoor FTP. Outdoors you have better air cooling and benefit from momentum. There’s a few other items which I forget. My shorter term power is a bit higher. For longer efforts I am not the norm though, as I can psychologically push harder when I don’t have to worry about traffic, falling off a speed etc.

I am also unsure what time periods that intervals/ xert calculate using. Say it’s based on 3minutes hard interval can you actually sustain it for an hour. I certainly couldn’t sustain what intervals was calculating for me for an hour last year.

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Thanks for the input. I did a few of the Kolie Moore Baseline tests when I was building up my SST intervals, but it’s been a few months since I’ve done any TTE efforts. I think my recent training focus on shorter efforts is messing with the calculations a bit. As much as I’d love for my FTP to be that high, I’m realistic in knowing it’s not.

For intervals.icu, you can change settings so that CP is estimated on 1800 sec efforts to avoid basing the estimate on short efforts.

For xert, your experience is different from mine. My TP keeps slipping since I switched to a polarized approach with harder shorter efforts. My HIE gets higher, but it’s definitely not overestimating my FTP.



Interval.icu calculates your eFTP from a max effort in the 3 to 12 minute range, afaik. So if you have good 5 min power, it will overestimate. As @_Matthew says above, you can change the time setting to something longer to prevent that.


Just do a 40+ minute test and find out for sure :slight_smile:

Honestly based on the power curve it looks like the ramp test number is pretty accurate for you - it could be a little low but not 20-30 watts low based on the curves

Side note - you see tons of people complaining about overestimation from the ramp test because these people get assigned workouts that break them. You don’t see tons of people complaining about underestimation because their workouts aren’t breaking them, so they still can make progress and it doesn’t frustrate them to the point of coming to the forum to complain. Statistically speaking - it should be overestimating for as many people as it is underestimating


This reads like riding with power also outside is rather new for you? Because, if it wasn’t you would already have a good impression of your capabilities indoors vs outdoors and you would most probably would have discovered said discrepancy of test results earlier.

I don’t think it’s too broad a generalization to say that all three tests are prone to rather the same errors or rather either a) reliant towards a medium distribution of capabilities of riders in regard to their energy systems or b) the contribution of anaerobic to aerobic energy systems. Can’t say for Xert for sure (haven’t had a look into that for quite a while) but we all know the ramp test very well and Intervals uses a mix of Morton’s 3 parameter critical power model or a maximum effort of a recent activity of required lengths and looks how they compare - than takes the higher one.

So my assumption is: yes, you seem to belong into that very big field of people (personally would guess it’s the majority but don’t know any source which would quantify that) who can produce more power outside than on an indoor trainer.

Should your respective targets indoor vs outdoor reflect this? Absolutely.

I’ve been cycling less than 3 years so yeah, I’m still pretty new to the game. And only training with power for a little over a year. So I’m still getting the hang of it.

And honestly, it’s not an ego thing wanting to take the highest FTP, it’s that I want to train accordingly. If it was 5-10W difference I wouldn’t really pay much attention but it was a big gap that had me thinking, “Hmm, maybe I should set my outdoor targets a bit higher.” I’m going to experiment with outdoor targets and see how it goes.

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You shoud post your signature in order to better understand how the ramp test will play out. Your Peak Power and High Intensity Energy contribute to the effort and without them, FTP cannot be estimated. Also post previous Xert Breakthroughs since they will help inform how the signature variables work for you.

Unfortunately a ramp test is a poor assessment of your 3 variable signature in Xert since there isn’t sufficient information in the maximal effort to understand their relationship. Ways to improve the assessment is to have older breakthrough rides with more than 1 point of failure or, if you’re going to do a test to failure like a ramp or 20-minute test, hold on to your power at the point of failure. The way in which your power declines (MPA) at the point of failure is a function of your signature.

Here’s a good example of an effort to hold on, after failure is reached. MPA is the purple line:

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Here’s the ramp test

Unfortunately, I don’t remember what the Xert FTP was after the ramp test (from Tuesday). The Breakthrough ride was yesterday.

And the last “Breakthrough”

If you click “advanced mpa” on the ride activity with the breakthrough, you will see what changed (it’ll list prior values) as I find that easiest to look at. Gold will have all 3 parameters change, Silver is 2, Bronze is 3. Then there’s the fakethrough where there’s an adjustment (most likely down).

Some people recommend going for breakthroughs every 4 weeks (or maximal efforts).

Tried that, nothing changed.

And the Breakthrough was silver.

It’s impossible for your FTP to be 314W. You would not be able to sustain the 5 minute effort in your last breakthrough if that were true.

There was a bit of a discussion on the Xert FB group about ramp tests. Seems like quite a few people have a lot of trouble with them and find other efforts to be better in getting their maximal effort out. You may want to go back to 20 minute tests or see if Xert can properly pick up changes in your numbers during regular riding. If the changes are small, it’s usually a good indication things are spot on.

It’s not impossible for his FTP to be 314w with a 400w 5MP

My power profile in 2019 was similar to OP, with slightly higher 1MP (660) and 5MP (414) and my FTP was 290w

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