# How accurate is e'FTP?

I bombed my ramp test on Tuesday and got just 238w. On tonight’s session (albeit with ERG switched off) it was obvious that it was too low, my first 10min block was 283w and my 20min max (including a 2mins 50% recovery) was 262w which calculates (@95%) an FTP of 249w. Intervals.icu however calculates an e’FTP of 256w is that an accurate enough number to train off ?

Just take the ramp test again - 30 minutes of your time?

Or, since there is hardly any difference between 249 and 256 you could choose either or split the difference and then increase it later if you think workouts are too easy.

I’ve found it pretty close. Close enough that if one is very different it’s time to test.

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Ramp test has both underestimated my FTP and been pretty close. Haven’t used intervals.icu recently, when I did it overestimated FTP and I had to tweak the setting.

Personally I think everyone is better off learning to ride at FTP for 20+ minutes, ‘walking a tight rope’ just above and below your threshold is valuable skill in addition to helping you estimate FTP. If you are going to put in hard work training, why take the easy way out and be guessing? Put in the effort and learn to feel where your threshold is, keeping in mind it can fluctuate a bit from day to day (and IMHO another reason to turn off erg).

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I would not use 95% of a 20min effort from a workout as the 95% calculation assumes a specific protocol (5min max effort prior to 20min effort) and then a maximal 20min effort. None of those apply to this situation.

My knowledge of most modeling approaches is that they are looking at maximal efforts of a sufficient duration(s) to feed into the model to generate the estimate. I would not use the modeled FTP based off of data from a workout as those efforts are likely not ‘maximal’.

I would either redo the ramp test or find a way to repeatedly generate maximal efforts of a similar duration to feed the model (I use 10mile zwift TTs events.) I believe intervals.icu, with the default model, overestimates my FTP so I do not use it directly but use it as a guide for adjusting my estimated FTP and then use feedback from Threshold or Over/Under workouts to make sure I’m in the right ball park. I felt GoldenCheetah was a little closer, but I had to do two maximal efforts in a short timeframe and I guess I’m lazy and wasn’t always doing the short interval which messes it up.

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In my experience, no, it’s not accurate. It consistently overestimates by a large margin for me.

I wouldn’t mind if it were right though, since it says I have a 360w FTP.

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According to this study, the warm-up protocol doesn’t make any difference.

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For me it is apples and oranges. I use the ramp result to calibrate my indoor workouts and eFTP to track my outdoor load and performance. Both work well in their space, but do not compare directly because their are measured with different sensors (PM vs. trainer), at different locations (pedal vs. wheel), on different bikes and in different environments. The fact that the offset between the two is reliably 10-15w, which probably accounts for drivetrain losses and better cooling, tells me that both are reasonably accurate in my case.

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My understanding of the 20min test protocol that the 95% is derived from is there is a warmup, then a 5min max effort to deplete anaerobic ‘stores’, then a specific rest period, then the 20min max effort.

Taking 95% of a random 20min max effort and calling that your FTP is like doing a random 1min max effort and saying your FTP is 75% of that power. 75% of 1min power is the FTP estimate in the context of a specific protocol (ramp test) but without the protocol loses its relevance.

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No matter what the study suggest I think most people would think there is a difference. If you are putting a full effort in for 5 minutes prior to the 20’ test even with a recovery window then that will make a difference.
I know I would (and have) found I can produce better numbers without the 5 minute effort.

I would have thought so too, but apparently not, at least based on the only formal study that seems to have ever been done.

Did you even read the abstract? FTP wasn’t determined from a ramp test, but from 20 minute tests done following various warm-up protocols.

Now it is true that the abstract doesn’t describe the subjects’ training backgrounds, but they had to be reasonably serious cyclists to have an average VO2max of 66 at age 35.

Sorry I’ll delete my message , talking shit, miss read “Participants performed a ramp test for determination of RCP and maximum oxygen”, and the miss understood the whole point of this test to examine the relationship of RCP and FTP, regardless of the warm up

It’s not at all accurate if the increase in your short power relative to your long FTP power is significantly more or less than average.

The estimates I get are consistently too high because on the percentile charts, my max power at 3-5 mins is relatively higher than 20-60 mins. Just like ramp test sets ftp to high if I’ve been training shorter high intensity power, but is ok in winter if only doing base/SS for a while.

I wish it was the opposite for me as I spent all spring doing high volume SS and sustained power plans, but I cannot quite hold the eftp value for a completely fresh 20 min effort / 10 mile TT, much less 40+ mins for a true ftp/tte!

Separately I finally did a 1 hr SS effort for first time ever recently, kind of preparing mentally to try a Kolie Moore style ftp test. I’m now a convert to that mindset and need to post in that thread - it’s well worth a read.

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Ps… If you highlight in TR just from first of the main 4 intervals to end of the last one, what is your average and NP for that duration? That is probably the most meaningful starting point you have to set a FTP and TTE. It’ll tell you what you can definitely do for ~46 mins as a baseline, assuming you were well worn out I’m this workout, which I’m guessing may be the case as the later intervals declined a bit from the first.

That could be a good starting value for one of the Kolie Moore style tests to confirm or find out if you have a few watts more beyond that.

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For me the eFTP was 1w off my Ramp Test FTP… and when I didn’t do a Ramp Test for awhile and did a new PR effort for 25 ish minutes, it raised the FTP 3w on the eFTP…

Same thing when I had to take 2-3 weeks off cycling due to my knee, said my eFTP was 280 when coming back, changed TrainerRoad to 280w and felt very correct during my first SSB workouts

YMMV I guess…

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Thats about right. If your short duration power is relatively good then you need to configure a longer minimum estimation time in /settings. I have mine set to 5 minutes because my 1m and 3m power are good. I have a 7-8 minute climb near my house that is a good test.

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So how well feed is your power duration curve? Since eFTP is derived from the PDC, lack of true efforts are going to skew the prediction (e.g. descriptive vs prescriptive). And do you or anyone besides Intervals.icu knows the critical duration that determines the fit? What is the estimated CP on the site for Morton’s 3 parameter or Monod & Scherrer’s 2 parameter? If you are a seasoned athlete, it should be around 5% but you should do the test for each model to get a “good” estimate. So at least two more tests (CP tests spans multiple sessions) over at least two weeks to tell if “your” eFTP matches reasonably.

If it was me, I would just redo the ramp test or the Kolie Moore’s Baseline FTP test (mainly to determine my TTE).

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agree if you are talking about mFTP (WKO)… some terminology:

• WKO uses mFTP (modeled FTP) and relies on a well fed PDC (max efforts for short, medium and long durations)
• intervals.icu uses eFTP and its based on a single short/hard effort (Morton’s 3 parameter model last I looked)

better yet, if you do the ramp test then use results to set pace for a longer test (Friel’s 30-min test or Moore’s or time trial). Find your actual limits on a longer test.

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Good call. 46min NP is 250w which is close to my 0.95 the 20 min max (249w). eFTP is marginally higher at 256w. For tomorrow’s 10mile TT I’ll aim for just below 20min max (260w) and perhaps up it slightly in the last bit if I feel I can.
I used to know my body better but I’m having to start again post losing 3inches of my bowel in a bowel/colon cancer op. The subsequent chemo and things have made it harder too. My legs still feel they can push more but I think the mind is stopping me

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