How I overestimated my FTP - Lesson Learned

I did my first ever FTP test (RAMP TEST) with TrainerRoad back on July 3rd 2018.
I was using the Elite Turbo Power Muin B+, its a great trainer, direct drive and very quiet with an inbuilt power meter (not a real power meter), the Misuro B+. So…this is what I did my first every FTP test on. The result was 238 watts.

From there I started the full distance triathlon plan and my FTP numbers were as follows:

August 2018 - 273
December 2018 - 280
May 2019 - 312

I was very happy with these FTP numbers, I always put it down to the fact that when I was younger I was very fit, I represented Ireland in Tetrathlon [running, shooting (like the skiers in the Olympics), swimming and cross country horse riding]. So I kept telling myself “its muscle memory Phil, your body remembers, this is why you are pushing such high numbers”. I also climb some big mountains around the world so presumed I had a big base. Oh, how I was wrong.

Last week I decided it was time to get a Garmin Vector 3s. I’ve always wanted one as it would be great to have real power numbers for my commute. Around the same time coincidentally I moved from Base into the Build phase of a half distance plan, bring on the v02 max sessions!!! I started using the new power meter instead.
From here I was not able to complete any of the vo2 max sessions, I was able to get halfway and then failed miserably. I decided to get a powerful floor fan because I thought my RPE might be high due to core temperature…this got me a little further but I was still failing.
I decided to test both power meters together, the Muin B+ was reading at 200 and the Garmins were reading at 190. Ok I said, ill reduce my FTP from 312 to 302 and try again. The same thing, failing vo2 workout.

I decided that it would be best to do another FTP test, this time with the new power meter. I was a little shocked and saddened by the result (and embarrassed, only because I was sharing the wrong info all along). The result was 264, a full 48-watt reduction from where I thought I was. I was happy that I understood why I was failing workouts but sad that I was not as advanced as I thought I was.
Seemingly, when the Muin B+ goes above 300 watts, just like what would happen in an FTP test, the wattage number its produces can be way too high, in my case, it was 48 watts too high.

So now I’ve adjusted my FTP and am looking forward to actually getting through the vo2 max workouts for a change :slight_smile:
I started to doubt myself mentally, thinking that I was too weak to get through it, all sorts of things were going through my head, “am I sick? am I weak mentally? is this as far as I go?” I even started reading the book Endure to see if I could glean any info (its a great book by the way).

I decided to share this because someone else may run into the same issue with this trainer and or overestimation of FTP.

I love TrainerRoad and the community here. It’s such a great learning experience and I’m very grateful. Thank you all.

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Rule Number One: Anytime you change power measuring devices, you should redo your FTP test.

  • Personally, I think the “should” above is a “must”.
  • Even “good” power measuring devices (meters and trainers) can and will vary from each other. There are absolutely no guarantees that watts on one will match watts on another. This is even more true with “budget” devices that may or may not be giving realistic power data. Too often, we see results just like you experienced.

Somewhat off topic:

  • I had a look at what might be your Career page. You just did a Ramp Test with the new Vector pedals. It looks like that was a 340 watts max 1-minute effort. That is multiplied by 0.75 to get to an estimated FTP of 255 watts.
  • But you seem to have 264 watts set in your Career page. Did you get a different FTP result from the Ramp Test or manually adjust the value?
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It’s been said many times - new power source - new FTP test. Lesson learned :slight_smile:

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You are 100% correct, I was debating if I should add this info to my post or not, trying not to confuse things.
The FTP result came in at 254, I quit early when I realised what was happening so I have decided to bump the FTP up 10 to 264.

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OK. Just make sure to evaluate your next couple of workouts and be sure that they “feel like they should” for intended difficulty.

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Will do Chad thanks.

When I say I quit early what I mean is I probably only had 1 or 2 more steps of the test in me. Im equating 2 steps to 10watts, but i’m just guessing there, I could be completely off with that?

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2 full steps would raise FTP by .75 x 2 x the step size. Probably more than 10 watts, but I’d be really conservative with that, since it’s really easy to overestimate how much more you could’ve/would’ve done after the fact. I think most of us probably think we could do more about 15 minutes after finishing a ramp test.

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I already ran the numbers and expect 2 steps is highly unlikely. I didn’t post anything since the current manual adjustment is possibly a bit optimistic already, but workouts and proper evaluation of efforts should flush that out.

Overall, I would recommend a full retest to have a better gauge than guessing. It’s one thing if you think you missed by a few seconds and fudge a few watts to “round” the numbers. It’s a whole different thing to estimate one or more minutes into a test. I just don’t see it being practical considering how the test is manageable until it really isn’t. And that switch can hit awfully fast… :stuck_out_tongue:

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Agree. I would either test again, or run with the 264W and see how it goes. I would not recommend adding any more. If workouts are failed in the first couple of weeks, dial it back to 255 and train there.

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Yep agree with you both. I’ll get another test done soon I think.

Just wanted to share my overall experience so that it might help someone else.

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It’s a good reminder for sure. No doubt that it will happen again to someone else, so it’s worth discussing in the open to help others.

This mirrors my experience exactly with a Kickr 17 that wasn’t calibrated. Ate crow for a while when I realized my FTP was actually 60% of what I thought it was.

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its not a great feeling is it? :sob::sob::sob:

Don’t feel embarrassed at 264. My most recent test was 265 and I consider myself to be a strong local rider. Not a racer or a triathlete, but 264 is nothing to be embarrassed about.

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Hey Russell,

I wasn’t embarrassed about the number, I understand its a good number :slightly_smiling_face:
I was more talking about the embarrassment of having told people I was nearly at 4 watts/kg. For example, im in talks with a coach and now Ill have to go back to him and tell him im 3.4 w/kg and not 4 :rofl::rofl::rofl:

But this experience and lit a fire under me so Ill get there!!!

Cheers,
Phil

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I had a similar experience. I’ve been using a dumb trainer and TR since 2013. My virtual power/FTP (since i don’t own a PM) was 260. Finally purchased a Tacx Neo & immediately completed the 8 min FTP test. My new FTP is 194. I’m going to try the 20min FTP test next to see how I go. Riding on a smart trainer is very different to using a fluid/dumb trainer. It’s definitely a game changer…for the better!

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I’ve also been there…

Just take a look at my power curve early 2018 (light blue) measured with my Bkool Pro trainer and late 2018 (dark blue) measured with a powermeter Rotor Inpower (close to 100W difference in a 20m test)

At the end of the day, it’s very difficult to compare different power meters (even “real ones” vary a lot depending if they are one leg, two legs, crank, spider, hub, …). For me, the power meter is useful to measure your own progress, but not so much to compare against others.

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I recently switched from Stages L/R to a Quarq DFour and immediately did a new ramp test. Was bummed to see a 10 watt drop in FTP but that’s how it works!

Side note: make sure you create a new “season” in the TR Analytics web platform so you can effectively compare new PR’s against your current power meter rather than all time. I was getting discouraged after big efforts that I wasn’t hitting any all time power PR’s but realized it’s wasn’t apples to apples since the stages read so much higher.

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Permit me a bit of a grumble about the commonplace that the absolute accuracy of power meters is irrelevant if a particular power meter is consistent with itself, since the latter will show you how you are doing in your own training even if not how you compare to others. At my age there is little point in comparing myself to other (younger) riders, so the only thing that does matter to me is how my training affects me.

But the data for even that can be seriously misleading if I change measuring device — which of course we regularly do, as I have, and as this thread shows. Do the math. The high end of Sweet Spot is just 10% of any given FTP from the low end of VO2max. A 10% absolute discrepancy between two devices — seen in the posts to this thread and in my own experience — could result in a TR blue hill claiming to be in my Sweet Spot, which I should be able to sustain for the better part of an hour, day in and day out, when it is actually in my VO2max zone, which I can’t maintain for more than a few minutes at a time without good recovery. Or vice versa. Those are really different training prescriptions for the same “real” FTP, and at least one is the wrong one.

The advice given here — to retest if you change devices, and also to check how your workouts feel when you do them with the new meter — is practical. But there is some irony in it. You’re doing the #% extra ramp test — using your body as the standard! — in order to measure the pricey new gadget which you bought to measure changes in your body. You’re using RPE, an acronym for “how it feels” to calibrate an “objective” meter. Imagine this very indulgent attitude applied to the accuracy of thermometers to measure body temperature. “Is a temperature of 106 serious?” “Well, thermometers are different, so it depends. Use that same thermometer for the next couple weeks, see how you feel, and adjust the numbers accordingly."

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I think that’s a bit of an incorrect summary of the comments above. Most of those types of comments relate to CHANGES between power devices.

  • If you are planning to use 2 different power measuring devices in the course of training and racing, it is best to use them together, at the same time, at a variety of power levels (below & above FTP) to see how they compare to each other.
    • Something like the DCR GPL comparison graphs is nice, but even a quick side-by-side of two power displays is better than no comparison.
    • That process is not always possible depending on a variety of incompatibilities (2 sets of pedals, 2 sets of bike specific power meters, or any other mismatch that prevents them from running simultaneously).
    • Using a 3rd power meter or smart trainer as a go-between can and does work, but not everyone has that option either.
    • That leads to the final option being using the rider as that go-between and using a Ramp or FTP test being one practical (and hopefully repeatable) option to try and gauge the differences.

Each one of the options above has a level of accuracy that can and will vary. Some are better than others, but people may well be restricted in what they can do. So having the rider be the intermediate may be less than perfect, but the only way to make it happen.


Somewhat off topic: It would be amazing if we could take all the power measuring devices at face value and trust their numbers. But I think we all have seen enough examples that we know that is not a practical or safe assumption. I don’t see people arguing against accuracy, but more dealing with the fact that we can’t necessarily trust the wide range of meters and trainers in all cases.

That leads to some level of testing or evaluation by the owner of multiple devices if they hope to use each one to the best of it’s capability.

If we want more accuracy from the manufacturers, that will require the continuation of testing by many people (especially the guys like DCR and GPL to make any issue more widely known), but also from any of us that may have access and ability to do testing on our own. Broadening the sample size and demanding the level of accuracy claimed from the makers is a requirement and part of the whole free market exercise to force them to give us what we want and what they claim.