Importance of an Accuracte FTP

Within reason, how important is an accurate FTP? For example, is +/- 3% close enough to set appropriate training zones?

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2x8min test, been doing it for years. Questions/answers regarding the validity of FTP testing formats isn’t really the point I’m getting at though. The question how accurate does an estimation of FTP need to be to provide effective training zones?

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Considering the difference between working in sweet spot and working in Tempo is such a small difference, I’d say it’s pretty important to get as accurate number as possible.

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In a thread I posted in this morning about ramp tests over estimating your FTP, if you think you over tested, it’s alway better to err on the side of caution and use what you think is realistic.

If you are experienced with indoor training and have a really good gauge on your RPE, then try a classic 2x20 min threshold workout at 95% to see how realistic that FTP test is of 324w may be a good idea. Do you think you could do 308w for 20m without too much trouble? This could be a good guide for you.

@Ian747 That’s a good suggestion regarding the 2x20 Threshold workout. A week ago a did 310W for 20min without too much trouble, and I certainly think I could’ve handled another. Thanks for the input!


If you are working in the threshold zone the same adaptations occur at 100% and 95% of FTP as far as I know - so 307W to 324W, you have power meter error zone (usually 2%). So there is no point of pinning your FTP to the single watt. I would go with 310-315 and see how it goes. And if you want some more confirmation about this:
Empirical Cycling Episode 3
Empirical Cycling Episode 16

The other workouts I have found to be a good gauge are are over/unders where I’m able to average approx 103-105% or so for a 4x12min. or 3x16min. These require a little more depth in fitness but still should be doable for you if it’s an accurate FTP.

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I have this feeling this is one of those humble brag threads. Anyway, sure, start at 315 and nudge it up, it’s not like anyone will be racing any time soon.


I have nothing to add but …

On behalf of all masters athletes around the World, I hate you. :stuck_out_tongue:

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Nice numbers, have also had big jumps and as I’ve stated elsewhere, when things like this happen, big jumps I find I start “yoyoing”… so I would be wary, increase by half , follow your instinct, get a feel on how well your doing your workouts and adjust as required.

My N=1 on doing this, is that my training has only suffered when I’ve gone with the big jumps and have ended up failing workouts, which has had a detrimental effect on my fitness and head! Therefore now I’m aware of this and ramp up more steadily, spend a week with that added few percent and if it feels good move FTP up towards the tested one… if I’m having a week of the intensity being set to 97% to complete, then after a week I move ftp down by 3%.

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I deleted the part about my threshold numbers so we can focus on the actual question. I just figured it provided useful context as to WHY I was asking the question, but I guess not.

For what it’s worth, just because a number seems unrealistic to you doesn’t mean that it’s impossible for everyone else.

Once I started believing that successful riders were no different than me, and started doing the kind of work that I knew made them successful, I started seeing big improvements.


I don’t think second guessing results is necessarily a bad thing especially if they illicit an ‘oh shit’ response. At the end of the day, if you prepped everything and kept your training setup consistent then the numbers don’t lie. It could easily be that you were on a flier that day and may not be able to replicate those conditions for your workout, but I sorta doubt it. Usually those kinds of efforts happen on race day.

As for setting zones between daily fluctuations in performance, precision and accuracy of the electronics, and the nature of reporting the data, I wouldn’t worry too much. Try your workouts, and if they’re too hard bump 'em down.

What phase are you starting or in the middle of?

I just went through SSB HV 1+2, and now I’m revisiting SSB HV 2 since racing has been postponed.

I think I’m going to set it at 315W and nudge up if necessary. Appreciate all the feedback though!

Often times people see a pretty big bump through base, you might be one of those people! Rock on!

IMO this is why knowing (as best as possible) LTHR is useful. Meaning, all things equal, when more “fit”, power will be higher at the same HR.

As for % power +/- in the OP…I think the PM accuracy is reasonable. So for my Quarq it’s 1.5% and I’d error on the conservative side at the most. So -1.5%. With that said, I’ve found that the power I can during the traditional 20 minute protocol -5% is too high. I reduce by 10% and that seems to align with my TTE perfectly…HR metrics also align.

Bottom line, everything I’ve read and listened to indicate most over estimate FTP and zones are set way high.

I don’t disagree at all, that’s why I have my view on the next steps.

I think the answer is probably yes but also no. Yes in the sense that like, you want to have a valid test result so that you can get a picture of this particular component of your fitness and track progress via that metric (“valid” meaning it actually approximates MLSS). So in that sense, yeah, you don’t gain anything by overestimating (or for that matter, picking a test result from a day when you were really on a tear and it’s a performance that’s not generally replicable).

But also i think “no” because remember that (i) all of these “zones” are really ranges; (ii) these ranges can be a little different every single day, so no matter what, you have to get a feel for what the workout is supposed to feel like and adjust if things are off; and (iii) when prescribing training above FTP, % of FTP starts to become kind of a crapshoot. So like 120% may or may not be the power YOU should be working at for Vo2max intervals, in other words. So no matter what, you have to adjust any plan based on your unique physiology, and approach it as like “is this the right power and duration for these intervals” rather than “is this the right percentage of my FTP.”

TR and other canned plans set themselves up based on FTP %, my guess is because it’s accessible and it lets people get started easily. Simplicity is a value. The downside is I think it gives an illusion of precision that really cannot be achieved, no matter how accurate you can estimate MLSS on a given day.

If you really are into cycling and serious about racing a lot, consider getting a Wko5 license. Provided you are feeding it quality data at various durations (and if you’re racing, you probably will be giving it plenty of good data). There’s a learning curve to it but it can provide some pretty deep insights.

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