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Using a 60-min TT to determine FTP doesn't always work

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01 / Original postUsing a 60-min TT to determine FTP doesn't always workZimboNC · 8 Nov 2006 02 / This pagePosts 1–13Page 1 of 1 · chronological order 03 / Latest replyPost #13rmur17 · 10 Nov 2006

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Power meters
Published
8 November 2006
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10 November 2006
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ZimboNC
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FTPGroup riding

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  1. Original post
    ZimboNC
    Archived post
    #1

    It seems obvious that the best way to determine one's 60-minute power (aka FTP) is to go out and ride all out for 60 minutes.

    My only "problem" with the 60-minute TT as the means of determining FTP is that I cannot seem to find a convenient stretch of road that long that would be conducive to such testing. I've been able to find a 20-minute stretch that works pretty well, but for an entire 1-hour effort I've found that the rolling hills, stoplights, numerous turns, and car traffic make it difficult to pedal all-out the entire time. Coasting of any sort absolutely destroys my average power number.

    Consider one of my recent 1-hour tests performed on a loop-course in a rural but populated area near me. Even though I was trying to treat it as a TT effort, the ride file shows that I wasn't able to pedal a whopping 8% of the time! The VI for the ride was 1.13! Call me a weenie but I'm not willing to run red lights, pedal hard down hills in traffic at over 35 miles an hour, or take up the entire road making a turn so as to be able to keep the power down.

    I know I could put the bike in the car and drive somewhere flat and remote to do my testing but that's not particularly convenient. What I've done instead is compare two measurements:

    - 0.95 x 20min AP
    - 60min NP

    Fortunately, these seem to correlate fairly well so that's what I'm using as my "working" FTP. Anyone else do this?

    --Steve

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  2. frenchyge
    Archived post
    #2

    Not using those specific measures, but I've never done any formal FTP testing because of some of the inconveniences you've mentioned. Still, I take the similar approach of using several different estimating methods to improve the quality of the estimate.

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  3. ZimboNC
    Archived post
    #3
    frenchyge said:

    Not using those specific measures, but I've never done any formal FTP testing because of some of the inconveniences you've mentioned.


    So how do you determine your working FTP and how often do you check to see if it has improved?

    --Steve

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  4. RapDaddyo
    Archived post
    #4

    You might want to do three max power test rides (e.g., 2min, 5min, 20min) and use the Monod CP Model. If you choose test durations carefully and ride the performance tests when rested and highly motivated, you should get a pretty good estimate. There are lots of ways to estimate FTP, especially for training purposes. But, if one is going to do a ~60min TT it's helpful to really nail it down with a 60min effort.

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  5. frenchyge
    Archived post
    #5
    ZimboNC said:

    So how do you determine your working FTP and how often do you check to see if it has improved?


    Last winter I would use my 3x20:5 routines to estimate FTP. I didn't really trust myself not to go too hard on 2x20:5's and overestimate my FTP. Since I did that routine 1-2x/wk, I had ample checks of my estimate. Once the weather warmed up and I got out on the road, I started noticing that the drop-off point on my power distribution was higher than my FT estimate by ~10-15w, and I would regularly hit FT+10w NP on spirited group rides (ie, hammerfests) of over an hour. So, I bumped my estimate by 10w and didn't have any problems.

    So far this winter, I have a guess-timated stick in the mud for 'SST locating' purposes, and I'm keeping track of RPE during higher-powered intervals to gauge where I think the stick is relative to my real FT. So far, I'm thinking it might be a tad too high, but part of that might be that I haven't put my game-face on yet. 😠 🙂

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  6. fastcat
    Archived post
    #6
    ZimboNC said:

    So how do you determine your working FTP and how often do you check to see if it has improved?

    --Steve

    How about testing it via an hour's all out effort on a trainer?

    (I'm considering this).

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  7. Roadie_scum
    Archived post
    #7
    RapDaddyo said:

    You might want to do three max power test rides (e.g., 2min, 5min, 20min) and use the Monod CP Model. If you choose test durations carefully and ride the performance tests when rested and highly motivated, you should get a pretty good estimate. There are lots of ways to estimate FTP, especially for training purposes. But, if one is going to do a ~60min TT it's helpful to really nail it down with a 60min effort.

    Just to clarify you would then interpolate a value for 60 minute power and use that as your FT, or are you advocating using CP itself as FT?

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  8. RapDaddyo
    Archived post
    #8
    Roadie_scum said:

    Just to clarify you would then interpolate a value for 60 minute power and use that as your FT, or are you advocating using CP itself as FT?

    No, I'd use the values in the CP model and extrapolate FTP or MP for any other duration of interest. That's in fact how I do my performance testing -- routine testing of three durations.

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  9. Roadie_scum
    Archived post
    #9
    RapDaddyo said:

    No, I'd use the values in the CP model and extrapolate FTP or MP for any other duration of interest. That's in fact how I do my performance testing -- routine testing of three durations.

    Right, but FTP being 60 minute power and you not having tested for 60 mins, you would use the predicted 60 minute power from the CP model as FTP in cyclingpeaks and hence in your NP and PMC calculations. You wouldn't use critical power (the gradient of the line in the CP model) as FTP. I think you answered my question, but I don't think the answer was no. Perhaps I'm confused?

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  10. acoggan
    Archived post
    #10
    Roadie_scum said:

    FTP being 60 minute power and you not having tested for 60 mins, you would use the predicted 60 minute power from the CP model as FTP in cyclingpeaks and hence in your NP and PMC calculations. You wouldn't use critical power (the gradient of the line in the CP model) as FTP. I think you answered my question, but I don't think the answer was no. Perhaps I'm confused?

    Actually, I'd argue in favor of using critical power, i.e., the gradient (slope) of the line. At least, that's what I had in mind when I, e.g., posted the "Seven Deadly Sins". The reason for this choice is that the inherent assumption of the critical power approach, i.e., that there is a linear relationship between work and duration, isn't entirely true. Consequently, extrapolating from shorter efforts (i.e., ~3 to ~30 min) to longer ones (i.e., ~60 min) results in some overestimation. Ignoring the contribution from anaerobic work capacity (i.e., the intercept of the work-time line) tends to correct of this effect.

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  11. Roadie_scum
    Archived post
    #11
    acoggan said:

    Actually, I'd argue in favor of using critical power, i.e., the gradient (slope) of the line. At least, that's what I had in mind when I, e.g., posted the "Seven Deadly Sins". The reason for this choice is that the inherent assumption of the critical power approach, i.e., that there is a linear relationship between work and duration, isn't entirely true. Consequently, extrapolating from shorter efforts (i.e., ~3 to ~30 min) to longer ones (i.e., ~60 min) results in some overestimation. Ignoring the contribution from anaerobic work capacity (i.e., the intercept of the work-time line) tends to correct of this effect.

    Cool, thanks Andy.

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  12. Pureshot78
    Archived post
    #12

    [quote="acoggan"]Actually, I'd argue in favor of using critical power, i.e., the gradient (slope) of the line. [QUOTE]

    Interesting.. so to confirm, the CP is expressed in w/kg so that:

    CP 3.1
    AWC 231
    KG 86.4

    Time Work Watts W/Kg
    [font=Times New Roman]60[/font][font=Times New Roman] 11,445 [/font][font=Times New Roman]275 [/font][font=Times New Roman]3.18 [/font]


    But without the AWC my estimate would be:

    86.4 * 3.1 = 269 watts

    Correct?

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  13. rmur17
    Archived post
    #13

    [quote="Pureshot78"][quote="acoggan"]Actually, I'd argue in favor of using critical power, i.e., the gradient (slope) of the line.

    Quoted post said:

    Interesting.. so to confirm, the CP is expressed in w/kg so that:

    CP 3.1
    AWC 231
    KG 86.4

    Time Work Watts W/Kg
    [font=Times New Roman]60[/font][font=Times New Roman] 11,445 [/font][font=Times New Roman]275 [/font][font=Times New Roman]3.18 [/font]

    But without the AWC my estimate would be:

    86.4 * 3.1 = 269 watts

    Correct?

    yep. Of course CP doesn't have to be expressed in w/kg ... plain ole W is fine.

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