Wattage fluctuation in 20 minute ftp test

last night I was doing the trainer road ftp test on my Kickr. When I got to the 5 minute test and the 20 minute test in slope mode my wattage was reporting very inconsistently. It would go from 275 to 255 to 235 back and forth and so on. Is that normal? Is my pedal stroke that unsmooth? Is the reporting on the wattage to TR inconsistent?

I was also running Zwift in the background so I yanked the dongle for zwift incase that was interfering(both TR and Zwift were reading the same wattage) that didn’t make a difference. TR was running Bluetooth and Zwift was on ANT+ on different devices. I kinda got pissed off and gave up because I thought I was wasting my time and dropped my wattage for a couple of minutes in the middle. Then I decided I might as well finish out the 20 mitnutes for a hard workout and the experience for next time when I figure out the wattage. I ended up with a suggested ftp lightly lower than my currents so I’m sure had I powered through the 20 minutes I probably would have raised my ftp.

I know Zwift shows average fpt during a 20 minute test so maybe I should try that and not freak out about the inconsistent readings.


Can you share a link to the web site of your test, so we can review it.

My money is on the being a Wahoo ERG Mode Power Smoothing issue.
The 20-min test uses a combination of trainer modes.

  1. ERG Mode for all parts of the workout, except for the 5-min VO2 burn and 20-minute Test blocks.
  2. Resistance Mode for the 5-min VO2 burn and 20-minute Test blocks.

This matters if you have ERG Mode Power Smoothing enabled, because the ERG parts above will look super smooth (and are fake), and the Resistance parts (5m & 20m) will switch to very jagged looking power by comparison.

Example: This may not be your test, but it shows what I think may be your issue.

  • Note how smooth most parts of the workout are… and how jagged the 5m & 20m sections are.

Yet another reason I just learned… to justify why I HATE that Wahoo setting.

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@mcneese.chad so are you saying the in slope mode without smoothing my 5 and 20 minute portions look pretty normal?

Yes, the 5/20 sections in your pic are “normal” since they show real variation in power data. I am guessing you were in a higher gear (big ring on roadie?) which tends to show more fluctuation than lower gearing.

But that is what real power looks like vs the overly smoothed data in ERG from that Wahoo setting.


@mcneese.chad well i feel like an idiot. Yes I was in the big ring. I looked at a bunch of other peoples tests and mine looks about exactly the same.

Too bad I gave up in the middle. Chalk it up to a learning experience. I’ll do another test soon. I’m glad I finished it out so got most of the experience. I’ll know how to prepare for and what to expect next time!

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If you haven’t already done so, I highly recommend disabling the ERG Smoothing in the Wahoo app (see video above for instructions). This is the 2nd instance just this short week where we see that setting leading to confusion.

I hate it more than about anything else in this training world. That Wahoo offers it at all is a problem, but the fact that they default it to be enabled is so, so bad.

Switch it off, and get used to what “real power” looks like. You will be able to refine your pedaling and take more control than being fooled by that setting.


Sharing what I just made and put into the meme thread.

I do think we need to do a PSA of sorts, because it is just a bad setting. It’s been lightly mentioned by TR on the cast, but they take a soft touch considering their position.

I’m done being nice about it towards Wahoo. They are creating enough issues on a regular basis, I don’t see their position as defensible.

  1. It should be turned off by default.
  2. Even if someone chooses to use it, Wahoo should cut the settings so it is far less “smooth” and at least falls into the general realm of reality, compared to the fantasy land that it currently inhabits.

Thanks all! I read about power smoothing but until I actually looked at my ftp test and looked at others and read your responses on this thread I didn’t fully understand.

Guess I shoulda just pressed on with my ftp test. You live you learn I guess. I still got in a hard workout!