How is the estimated FTP being calculated?

[SIMMN]

I did the Zwift Elevation Evaluation route yesterday to refresh my FTP. Afterwards, I received this email from intervals.icu, screenshot below. But how is the estimated FTP being calculated?

I thought generally the 95% of 20-minute avg. would be considered as FTP. In my case, it would be around 284w which is kinda what I think is correct but where does the 293w come from?

[MedTechCD]

Search for ´eftp calculation ´ turns up this amongst other:

Eftp calculation formula based on effort

When looking at a workout the top row is populated with all sorts of values. Among them are eFTP en ride eFTP. If you click on one of them the following text is shown. “Estimated FTP is calculated using power curves from FastFitness.Tips and Morton’s 3 parameter critical power model. The algorithm requires just 1 maximal effort of between 180 seconds and 30 minutes. Your estimated FTP will stay the same if you maintain your training load and decline slowly when you reduce training. To get it to…

[SIMMN]

Thanks for the info and I would have to read those link in detail. But which FTP I should base on to plan my fitness training? The eFTP or the 95% of 20-m avg.?

[MedTechCD]

What is used as minimum duration for eFTP calculation in Intervals?
I would advice to use at least 5-6 min for min duration because otherwise people with high anaerobic power/capacity will get overrated eFTP.

You could play with that setting a bit and re-analyse the activity to see how it changes. If there’s a big difference with the default 3 min compared to 6 min, you may have high anaerobic power/capacity interfering with the model.

[SIMMN]

Thanks for the info! I do think I got over estimated…I tried to adjust the eFTP duration and check the eFTP changes for a particular workout, here are what I got…
3-6min eFTP duration: 298w eFTP
7-12min:293w
15min:289w
18min:288w
21min:281w
24min:273w
27min:253w

I think my ftp (measured on pedal) is around 282-ish…so what eFTP duration should I use then?

[MedTechCD]

If you plan to test regularly with longer all-out efforts, set minimum at 12 minutes or longer. But do remember that efforts shorter then what is set will not yield any result.
FTP estimation within about 10 watts is accurate enough. Don’t forget that FTP is not a static number. It changes day by day with your fatigue/mood/stress etc…
And you train in Zones, not to a fixed number. As long as you’re in the right zone, you’re training the right target.

[SIMMN]

Understood, thx!

I set it for 10min for now.

[Gerald]

I would say your FTP is about 255-260W, but without seeing your specific workout, and your recent history, it’s really a guess, and very difficult to say for certain. Also, it depends what your intention is w.r.t. training, or rather riding/racing.

It appears, from reading the few posts that your anaerobic contribution is quite high.

[SIMMN]

I know my FTP is higher than 260w but eFTP of ~290w gave to me from intervals seems high for me as well…I changed the mini-interval for eFTP to 15-min.