When I was using it, intervals did a not-so-good job of estimating my FTP.
See my edit. Basically any piecewise model would have to show a sharp transition, but the WKO model doesn’t.
ETA. Just to be clear. Something’s different between 1000 and 2000 seconds.
Where is that screenshot from?
Edit: Ah right, just an overlay from the article I linked I guess?
Let me try explaining the inflection point without derivatives: FTP is the hardest intensity at which you can go “for ever”. That gives an almost flat line, until “for ever” ends, that is the inflection point and power starts to drop faster.
Correct, from your link.
Why should power suddenly drop faster? Where do you think you have a greater drop, when you increase duration from 30 to 40 min or from, say, 100 to 110min?
Ok, but that’s really a very localized difference. If you have two pieces of a piecewise function you can just glue them together in a smooth way. Looks nicer and closer to the real world. Actually I had not noticed this (minor) difference between WKO and Peronnet Thibault. Maybe they just smoothed things out a bit. It would be a natural thing to do.
PS: I’m really just guessing! I have no insights into the actual WKO model.
Okay, thanks. It’s a head scratcher for sure, at least to me.
The way I see it is, there are two different types of fatigue kicking in. The max power curve drops quickly up to let’s say 10 or 20 min. That is the lactate level that prevents you from continuing at the same pace. Then there is the “for ever” moment, lactate is not building up and the next minute is the same as the previous minute. Until some other type of muscle fatigue kicks in at the TTE point, that makes the power then drop again faster. That’s what I make of it.
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Here is what Tim Cusick had to say…
and now this is what I stated (right or wrong):
And you and @Anna_K should feel free to correct what I said above.
I think this would be true if you were specifically talking relative to FTP, but when you look at a bigger picture it doens’t quite hold. Obiovusly, the power curve drops a lot faster leading into 10-20 minutes because the closer to your “max” overall power you are, the more lactate you will accumulate and consequently fatigue more rapidly. However, FTP is a pretty generalized number which is “hour power” but there stands to reason many people can’t hold their FTP for an actual hour and some could probably hold it a bit longer, based on what type of a rider they are. Let’s just call it an hour though because that’s easier. So if you paced a 60 minute effort as evenly as possible, then you would obviously start dropping off after 60 minutes IF you were riding all-out. But a power curve isn’t talking about the same ride. So you would expect that your 61 minute “all out” would be pretty dang close to your 60 minute “all out” because it’s only a 1.7% increase in total time. Whereas earlier in the power curve, you see big drops (usually) from say 5 to 10 minutes because that’s doubling the time.
Right, I get the difference of a power curve taken from 1 ride vs the max for each interval over various attempts.
We are talking about various attempts. I thought that the entire idea of that inflection point was how they define FTP over at WKO.
BTW is the discussion here just if the max power curve is differentiable at the FTP TTE or is it about that the slope before and after FTP TTE is the same or not?
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Anna, not sure where to reply here as so many questions above also. I will say a lot of the model assumptions inn this thread are wrong. I know the comparison was made between WKO model and the PT model but they do not match. Dr Coggan did an exhaustive 4 part webinar series to really set the background of all the work but lots of effort to watch them all. Focus on webinar 3, you will see the model testing and some good info there https://youtube.com/playlist?list=PLOhzd0zmrJzk9lahl9clZxUWgiwk2fBpu
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The hero bar metrics which are derived from the model are from the previous 90 days. You can use the RHE time ranges to for customizing the time in charts and reports which can be useful in comparing.
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@TimWKO yes that is another feature of WKO5 that I love.
We tested the model against all known existing models, here is a summary of results (there is more info on this in the webinars I linked above) but in reality, the WKO model tests best.
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I scanned the thread and maybe I can help a little with a few replies to some of the highlights.
- “FTP is a fuzzy area not a specific number” - Someone said something similar to this above and is something I say often. FTP is not a specific number, not a toggle switch that flips over on 1 watts, it is more “transitional”. The issue I see in a lot of discussion of FTP is this one watt toggle approach pushes an over precision that does not result in better coaching / training. As a coach, I always round my FTP (when I use it) to 5 watts; 270watts or 275 watts, never 273 watts. Just my system and not becoming overly precise.
- FTP is an inflection point, which simply means that power duration curve drops off the the “flat” (as referenced above) and “it ain’t coming back”. The rate of such decline can vary (see stamina). FTP is most closely related to MLSS which most people can sustain anywhere between 30-70 minutes. This is why we released TTE so people can see there FTP and how long they can hold it.
- The Power Duration Curve is actually smoothed by a few watts in that area. Look at the contribution chart and think about it this way. The Power Duration Curve is the sum of your aerobic and anaerobic power and the numbers will add up neatly everywhere except right around FTP as there is a few watts of smoothing there to better discern TTE and some other reasons.
4, FTP is not power you can hold for an hour. That was an easy way to observe FTP way back when we were figuring out ways to use power and could not determine TTE yet, the technology evolved years ago that lets us be more precise now so no reason to keep estimating at an hour. As someone noted, a fair amount of people cannot hold FTP for an hour and in my observation, that is more and more true NOT due to software but current approaches to training. - And finally, training has moved way beyond FTP now. As a coach, I am not sure I really use it for anything except TSS set points and as part of the whole athlete view. Ask yourself why do you use FTP for? It is a nice physiological marker but in reality, the whole athlete view of Pmax, FRC, Vo2max, mFTP and Stamina is robust and easy to determine now with power and give coaches much better tools. Do you use FTP for targeting zones? To general of an approach, way better to use iLevels or some other way of developing training intensity distribution targets.
Ok, sorry for long post, I am sure I missed a lot. Can follow this link to list of some webinars on the topic https://www.wko5.com/wko-educational-webinars
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PS - sorry for typos, my Mac keyboard is dying
Oh hi Tim. What an honor 
. The sun is just rising here. I’ll have a look at the webinar you mention during the day.
Perhaps one question before doing so (regarding point 4 of your answer): TTE. As a mathematical parameter in the model it makes sense (I’m sorry but without a concrete formula for the WKO graph I just have something like PT in mind). But I don’t see its significance for the user. Let me explain. As you say, FTP is a “fuzzy area not a specific number”, say we can “guess” it ±5w. But even for such a relatively narrow range, TTE will differ quite a bit (I could ride considerably longer at 240w vs. 250w, perhaps 1h20 vs. 1h, i.e. a >33% difference). Hence I find it weird that people pay so much attention to TTE around here when really their “improvements” in TTE are within the range corresponding to the unavoidable(?) imprecision of the FTP estimate.
This is why I’m pretty old-school and still guesstimate my FTP as 1h power. Because even if my actual TTE was only 50min, really the value I could hold for 1h would be almost identical (I think ).
As for your last point - training. I completely agree. I don’t think about my intervals in terms of %FTP. I’m not a WKO user, but I guess I subconsciously have something like “iLevels” in my head by which I train.
I’m with you. I think TTE is really just a marketing gimmick. I mean, it’s a real thing - for any given power such as FTP, obviously you can only maintain it so long - but claiming to be able to measure it with any accuracy or precision is something else. Even formal tests have a variability of 15-20%. The variability of TTE from a model has to be even greater, which makes it pretty worthlessness, if not at times misleading.
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