Road Cycling “It is by riding a bicycle that you learn the contours of a country best, since you have to sweat up the hills and coast down them. Thus you remember them as they actually are, while in a motor car only a high hill impresses you, and you have no such accurate remembrance of country you have driven through as you gain by riding a bicycle.” -- Ernest Hemingway

Strava FTP estimate

Old 04-27-19, 05:28 PM
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RShantz
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Strava FTP estimate

Curious how accurate you feel the Strava FTP estimate is based on your experience. It's fairly accurate for me, but curious what others feel.
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Old 04-27-19, 06:35 PM
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I don't think it's very accurate.
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Old 04-27-19, 06:36 PM
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https://www.velopress.com/how-accura...ind-and-hills/


its not great....check out the article.
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Old 04-27-19, 06:50 PM
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Interesting that it's most accurate on long climbs.
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Old 04-27-19, 07:28 PM
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I can make up a more accurate number.
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Old 04-27-19, 07:32 PM
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Originally Posted by Carbonfiberboy View Post
Interesting that it's most accurate on long climbs.
It's particularly accurate on approx 1 hr steep climbs where you go all out.
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Old 04-27-19, 07:49 PM
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Originally Posted by gregf83 View Post
It's particularly accurate on approx 1 hr steep climbs where you go all out.
It is most accurate at max effort at zero speed for one hour.
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Old 04-27-19, 09:43 PM
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Originally Posted by gregf83 View Post
It's particularly accurate on approx 1 hr steep climbs where you go all out.
That's about right. Because with that, it's just math to get very close to a metered FTP. So long as Strava has accurate variables to work with (rider height and weight, bike weight, cadence, etc) and the ride is a steady output up a constant grade for a reasonably long period, the Strava power guesstimate can get pretty close.

Now the Strava "estimated power" over a typical ride under normal conditions? Might as well be a random number generator.
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Old 04-27-19, 10:02 PM
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More accurate than rolling dice. Less accurate than an educated guess.
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Old 04-27-19, 10:08 PM
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It's most accurate on loops, circuit rides, which negate differences due to wind and elevation.

Same as the various online calculators for power/etc. These work best when wind is factored into one-direction segments and routes. Lends a dose of reality to my handful of top tens on Strava. Factor in the tailwind and my 300+ watts over 15-20 minutes turns out to be closer to 100 watts.

I've compared my Strava and online calculator power guesstimates against other folks my size who do use power meters on the same routes in the same or similar conditions. Close enough for my purposes. If it's off by 5-20 watts, no big deal. Until I can generate 200 watts over a favorite 5 mile training circuit, I don't need a power meter to remind me how wimpy I am.
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Old 04-27-19, 11:40 PM
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Are we talking about the ftp estimate from your power duration curve from actual power meter recording of your rides over a time period? If yes then I find its pretty close to 95% of my 20 min test so its pretty accurate.

Last edited by redlude97; 04-27-19 at 11:49 PM.
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Old 04-28-19, 05:47 AM
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Originally Posted by redlude97 View Post
Are we talking about the ftp estimate from your power duration curve from actual power meter recording of your rides over a time period? If yes then I find its pretty close to 95% of my 20 min test so its pretty accurate.
Yes, the FTP estimate. Not estimated power on segments. I tried my best to state this in the original question. I completely understand that the segment power is fairly useless. Really wondering thoughts on the FTP estimate.
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Old 04-28-19, 05:51 AM
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I think Strava utilizes more duration points to analyze data than 8min, 20 min or 60 min measurement points that we're familiar with which is logical to me.
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Old 04-28-19, 09:01 AM
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Originally Posted by RShantz View Post
Yes, the FTP estimate. Not estimated power on segments. I tried my best to state this in the original question. I completely understand that the segment power is fairly useless. Really wondering thoughts on the FTP estimate.
I knew before even opening the thread the majority of answers here would be completely off base. Try the training or road racing forums, trainerroad forums, or r/velo
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Old 04-28-19, 09:02 AM
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Originally Posted by RShantz View Post
I think Strava utilizes more duration points to analyze data than 8min, 20 min or 60 min measurement points that we're familiar with which is logical to me.
I'm not sure of the algorithm but I've populated my duration curve with sub 10 min power PRs without an effect on my estimated FTP
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Old 04-29-19, 04:29 PM
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The Elevate extension for Strava adds some potentially useful data including estimated FTP. Dunno if it's accurate. Probably depends on user-entered data. But it's been useful as a gauge of my progress on the same training routes I often ride. If the numbers trend upward, that's a fairly reliable indicator that I'm improving, even if the "FTP" number is relative only to itself within the context of the Elevate app.
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Old 04-29-19, 07:09 PM
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Originally Posted by redlude97 View Post
I'm not sure of the algorithm but I've populated my duration curve with sub 10 min power PRs without an effect on my estimated FTP
That doesn't make any sense.

Why would you trust that?

I recently popped off a big 90 day 1 minute PR and had a significant jump in FTP. Why? Because it was primarily an aerobic effort.
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Old 04-29-19, 10:02 PM
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Originally Posted by rubiksoval View Post
That doesn't make any sense.

Why would you trust that?

I recently popped off a big 90 day 1 minute PR and had a significant jump in FTP. Why? Because it was primarily an aerobic effort.
I mean I don't. That's kinda the point I was making, that whatever algorithms they are using dont take into account the entire power curve like WKO4/GC/Xert. Pretty sure strava just uses 95% of best 20 min effort which happens to be the way I test so its reflected in stravas estimated FTP
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Old 04-29-19, 10:19 PM
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Estimate is not so good. It is better on hills. Then a real PM reading means?
I'm a bit cynical..
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Old 04-30-19, 06:35 PM
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Originally Posted by rubiksoval View Post
That doesn't make any sense.

Why would you trust that?

I recently popped off a big 90 day 1 minute PR and had a significant jump in FTP. Why? Because it was primarily an aerobic effort.
So the Strava FTP estimator showed a significant increase immediately subsequent to your 1 min effort? That's really what I was curious about. On my account it's not using 95% of 20min. I think it's using a more complicated calc where it considers lesser duration also, but certainly wouldn't have thought 1 min efforts would impact the calc???
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Old 05-01-19, 05:50 AM
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Originally Posted by RShantz View Post
So the Strava FTP estimator showed a significant increase immediately subsequent to your 1 min effort? That's really what I was curious about. On my account it's not using 95% of 20min. I think it's using a more complicated calc where it considers lesser duration also, but certainly wouldn't have thought 1 min efforts would impact the calc???
No. I don't use strava for anything power related. And my ftp is always closer to 90-92% of 20 minutes.

WKO4 showed an increase in modeled ftp after the effort.

Most everything impacts that model. Even 1 second sprint power affects the model.
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Old 05-01-19, 06:04 AM
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Originally Posted by RShantz View Post
So the Strava FTP estimator showed a significant increase immediately subsequent to your 1 min effort? That's really what I was curious about. On my account it's not using 95% of 20min. I think it's using a more complicated calc where it considers lesser duration also, but certainly wouldn't have thought 1 min efforts would impact the calc???
I looked at mine for maybe the second time ever. It certainly seems to be based off of my best 20-minute effort (which gives a pretty pathetic result because the nature of my outdoor rides). I'll keep it in the back of my mind the next time I have the opportunity for a good 20min effort (which might be a while).
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Old 05-01-19, 07:44 AM
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Originally Posted by rubiksoval View Post
No. I don't use strava for anything power related. And my ftp is always closer to 90-92% of 20 minutes.

WKO4 showed an increase in modeled ftp after the effort.

Most everything impacts that model. Even 1 second sprint power affects the model.

To everyone, rubi is right in the above posts.

Lots of the shorter stuff contains a pretty disproportionate amounts of anaerobic input. This contribution is different by person. It is probably worse among people like myself without a huge base/aerobic engine like the racer boys and girls who ride 3x the hours I do.

I find for myself, the 90 to 92% also is much closer. Forget 95%, unless you're a long course triathlete or time trial person only. Then you may be closer to 95% as your anaerobic contribution to 20min efforts probably isn't as much.

I tested at 300 for 20min months back. It took appreciable time after that to get my SS workout power for an hour up to 260 even. Why? I had gone through series of weeks of workouts that topped up the LT2 and anaerobic engines and essentially prep'd me for a great 20min test.

Even a week or so after that test, I couldn't do 260 for an hour! It took a few weeks of SS work to do so.

Most folks simply don't have the engine to interpolate short duration power to hour power without sorely over estimating.

Lastly...........the best indicator of performance is performance itself. You want to know.......try it and see.
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Old 05-01-19, 09:56 AM
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I don't even have an option for estimated FTP...interesting.

I can tell you that it's estimated power on rides is awful.

To have a good idea of FTP you need to look at multiple data points, 5, 10 and 20 minute power. Or just do a full blown 60min FTP test, but that's not something I have any desire to do so I use estimates based on other data points.
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Old 05-01-19, 02:24 PM
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Originally Posted by OUGrad05 View Post
I don't even have an option for estimated FTP...interesting.
I think Strava offers that option to premium subscribers. Try the Elevate (formerly Stravastix) extension in Chrome. It adds lots of interpolated data/guesstimates.

I find it useful for longterm evaluations of my fitness and progress. 2018 was a rough year -- injuries and illness -- so it's been interesting to use the interpolated data to get an idea of my recovery. Just the past couple of weeks I've begun to match and occasionally beat my previous bests on 20-60 minute loop training circuits. Part of that is due to longterm physical therapy. Part is due to adding an aero bar to my old steel road bike for occasional use on flat segments; and getting a nifty old 1993 or '94 Trek 5900, which is much nicer for climbing. So my aero and weight cheats are probably skewing the interpolated data.

Yeah, a power meter would be more accurate. But I can't justify that when I struggle to average 160 watts over a 20-60 minute training ride. Just recently I've improved to averaging 175 watts (guesstimated). When I reach a guesstimated 200, then I'll consider a power meter. Well, maybe I'll rent or borrow one. I just can't see how having one would significantly improve my power. I'm never gonna see 300 watts over distance again, not at my age. But power meter data might offer either a nice attaboy bit of affirmation or, more likely, remind me that an aging human body is unimpressed by my rosy glasses.
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