I pull my data from Strava. I understand that the estimated FTP (pink) graph as shown on the Fitness page chart is calculated by intervals.icu based on a single 60s+ maximal effort. But I can’t figure out a few things.
Where does the data for the black FTP line on the same chart come from? The Strava setting?
How does the Set eFTP functionality affect the FTP line?
Does Set eFTP override Strava or the other way around or something different?
The black line is your manually entered FTP which is taken from Strava when you first registered with Intervals.icu. After that you can change it on each ride and set the default for future rides in /settings and whatever is in Strava is ignored.
The eFTP value does not change your manually entered FTP. You can choose to update your FTP to match eFTP if you want to.
Your training zone ranges are derived from your manually entered FTP.
Its actually now at least 3 mins by default (configurable in /settings). 60s was a bit short.
Thanks, David! That clears it up for me.
Creo que en tan poco tiempo al ponerlo en el FTP estimado para viajes cortos si puede ser no estoy seguro pero el mío lo tengo en 1h y hay bastante diferencia con el estimado y para mi es más seguro el que tengo configurado de 1h para viajes que hago largos de fin de semana que son de más de 5h lo veo más fiable corregirme si hay algo que no entienda gracias
Certainly a 1h TT will work but only if you are very good at pacing and suffering! Also FTP is supposed to represent MLSS (max lactate steady state) but the 60m duration is fairly arbitrary … real MLSS duration could be anything from 30-75 mins depending on the individual. So I think there is a lot of value in attempting to derive FTP power from shorter efforts.
This is a good read:
Hi, seems like a very cool tool, few questions:
Thanks!
EDIT: now it seems Power tab just broke… the short end of the graph dropped much lower than the actual data, haven’t found a way to restore it. Also estimated FTP graph in Fitness tab sometimes seems to break… namely the drop over time isn’t always reflected. Had to re-enter FTP data for the new season (changed 1w) to get it to correct itself.
Tx! Ride stats (intensity, load etc.) are always calculated using the manually entered FTP for that ride. New rides get whatever FTP has been set in /settings (indoor rides get the indoor one if it is different and this is based on the info supplied by Strava).
Training load for activities without power is estimated from the HR data if possible. This works best if you have a history of activities with power and HR. If power is available for an activity HR is not used for load calculation.
Estimated FTP (eFTP) is calculated from max efforts of at least 180s (configurable in /settings). It is carried over from ride to ride and will decay slowly if you reduce training. You can also reset it (e.g. after an injury layoff).
The FTP numbers on the /power page are calculated using the power curves shown. The default algorithm is the same one used to calculate eFTP so should be similar. You can select different algorithms in options (for interest really, the default works well and doesn’t have special data requirements). You can also read off an estimate of your W’ (anaerobic capacity, nice to fill it in to get the W’bal chart on rides, like Xert’s MPA).
If you do end up with a problem (e.g. power page broken) try reloading the app. If that doesn’t work post here and I will have a look!
Thanks for a quick reply, and got my power curves fixed by this: Power Spike incorrectly clipping sprints . Set the clipping to 999%. Never seen a random spike on my power meters anyway. Or in other people’s data even.
FYI as the other guy said, FTP and sprint efforts are not related, but seeing 200-500% FTP for is normal. I’d actually turn it off by default if I was the developer to avoid confusion. 20% probably affects like… 100% of users 
When I did the FTP estimation I had to add power spike fixing. I just takes one dodgy ride and suddenly you have 450w FTP. My PowerTap is very reliable and doesn’t spike but many others do, especially when running out of batteries or whatever.
The 20% is 20% above the power curve for your FTP. So if you have FTP of say 300w according to the curve you should be able to do 1000w for 5s. So if you do more than 1200w it gets chopped. People with good anaerobic power might need to bump it up.
hi all, I’m new to structured training. Been using Trainerroad for the past 5 months (I did the sweetspot base high volume & am in the middle of the Build high volume phase). I started at an FTP of 243.
Question: 3 days ago i did a TR FTP test that gave me 266, after a 5 day rest week. Today after 3 days of non-activity I did a Sufferfest 4DP test that gave me an ftp of 279 (see screenshots).
Training peaks analysis from both tests gives me a 20min power of 279.
Do I keep a 279 ftp from hereon to carry on with the build phase? am a bit nervous so could use some advice.
Thank you
Sech
If your 20m power is 279 then your FTP would be 95% of that using the usual rule of thumb i.e. 265w which matches the TR number. So use that.
I’d say that the difference between 265 and 279 is not that much, you could use either one. This won’t lead to any problems, but threshold intervals might feel too hard or too easy. If you cannot complete a workout — lower your FTP by 2-3% as TrainerRoad guys suggest.
And one of the best ways to use the FTP tests is to track progress. Every test protocol is faulty, but if you see that after training and recovery you get a higher number — congratulations, you’ve improved! Just stick to one type of test — you cannot compare different protocols.
Though sometimes you can surprise yourself. The results of my 20 minute FTP on Zwift (95% of 20-minute effort, after warmup and priming efforts) and the 20-minute portion of the 4DP on The Sufferfest (this test is a bear, with the warmup, sprints, and the 5-minute all-out effort to empty the tank before the 20-minute portion) were only 3-4 watts different between the two (within 1.5%, probably within the margin of error), each done about 2 weeks apart. I was pretty shocked.
alright, thank you David, much appreciated. Fantastic work!
Thank good people. An interesting thought, so after taking a day off yesterday this morning I did a 4hr outdoor ride with the first 1hr TT.
Surprisingly I hit 299w for 21m so I see Int.icu recommends 286w ftp. Training peaks gives 284w. TP shows 1hr power at 245. I suppose it might not be a bad idea to run with the 284 ftp for my ego & continue into the TR build phase, if workouts are hard then I just decrease intensity by 3-5%
This is exciting & terrifying at the same time given that I’m going into threshold & vo2 max for the next 4 weeks, with my goal event in 6 weeks.