Go Back  Bike Forums > Bike Forums > Road Cycling
Reload this Page >

How to estimate FTP w/out a trainer?

Notices
Road Cycling ďIt 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.Ē -- Ernest Hemingway

How to estimate FTP w/out a trainer?

Old 09-04-20, 08:20 AM
  #1  
kosmo886
Senior Member
Thread Starter
 
Join Date: Mar 2010
Posts: 197
Mentioned: 0 Post(s)
Tagged: 0 Thread(s)
Quoted: 154 Post(s)
Likes: 0
Liked 7 Times in 6 Posts
How to estimate FTP w/out a trainer?

So I donít have an indoor trainer (other than a Peloton) and certainly donít have a road where I can ride all out for 20 minutes on. How else could an FTP test be conducted, or is really the best method to get on a trainer to do it?
kosmo886 is offline  
Old 09-04-20, 09:03 AM
  #2  
RChung
Senior Member
 
Join Date: Sep 2009
Posts: 1,818
Mentioned: 30 Post(s)
Tagged: 0 Thread(s)
Quoted: 514 Post(s)
Liked 469 Times in 185 Posts
Originally Posted by kosmo886 View Post
So I donít have an indoor trainer (other than a Peloton) and certainly donít have a road where I can ride all out for 20 minutes on. How else could an FTP test be conducted, or is really the best method to get on a trainer to do it?
Do you have an on-bike power meter?

Estimate CP and W' instead, from maximal shorter-duration tests. Then use CP instead.
RChung is offline  
Old 09-04-20, 03:31 PM
  #3  
InvertedMP 
Senior Member
 
InvertedMP's Avatar
 
Join Date: Mar 2020
Location: Bay Area, CA
Posts: 334

Bikes: 2021 Scott Addict RC 20

Mentioned: 0 Post(s)
Tagged: 0 Thread(s)
Quoted: 169 Post(s)
Liked 260 Times in 102 Posts
You can do an FTP with the Peloton.
__________________
www.mp-aviation.com
InvertedMP is offline  
Likes For InvertedMP:
Old 09-04-20, 03:43 PM
  #4  
MoAlpha
ē ó
 
Join Date: Jun 2015
Location: Land of Pleasant Living
Posts: 8,436

Bikes: Shmikes

Mentioned: 53 Post(s)
Tagged: 0 Thread(s)
Quoted: 6559 Post(s)
Liked 3,057 Times in 1,669 Posts
intervals.icu will generate a power curve based on any all-out effort > 3 min using Morton's 3 parameter critical power model, FWIW. Mine actually has a pretty good fit for efforts from 1 min to 1 hr.
MoAlpha is offline  
Old 09-04-20, 05:20 PM
  #5  
mattcalifornia
Senior Member
 
mattcalifornia's Avatar
 
Join Date: Jul 2020
Location: Ellay
Posts: 160

Bikes: 2002 Eddy Merckx Team SC Resto-Mod; 2019 Ibis Hakka MX; 2017 Spot Brand Ajax Belt Drive

Mentioned: 1 Post(s)
Tagged: 0 Thread(s)
Quoted: 87 Post(s)
Liked 91 Times in 54 Posts
Originally Posted by InvertedMP View Post
You can do an FTP with the Peloton.
Yes, but unless the Peloton is properly calibrated (which many - or even most - aren't), the FTP result won't be useful for road riding.

Drive your bike somewhere you can find a suitable road. There must be somewhere within an hour of you.
mattcalifornia is offline  
Likes For mattcalifornia:
Old 09-04-20, 06:06 PM
  #6  
RChung
Senior Member
 
Join Date: Sep 2009
Posts: 1,818
Mentioned: 30 Post(s)
Tagged: 0 Thread(s)
Quoted: 514 Post(s)
Liked 469 Times in 185 Posts
Originally Posted by MoAlpha View Post
intervals.icu will generate a power curve based on any all-out effort > 3 min using Morton's 3 parameter critical power model, FWIW. Mine actually has a pretty good fit for efforts from 1 min to 1 hr.
Not any. For the Morton 3-param model you'll need at least 3 all-out efforts. You'll get slightly better (more robust) results if the all-out efforts are reasonably steady, though a nice thing is that they don't have to be slavishly steady. Also, the results will be slightly more robust if the shortest and longest efforts aren't too close together in duration, so maybe 3-4 minutes, 8-9 minutes, and maybe 16 or 17 minutes. The advantages of the CP/ W' model are that you get twice as many parameters to evaluate your condition than FTP, and you also get a way to assess the consistency of the tests.
RChung is offline  
Old 09-05-20, 07:55 AM
  #7  
Sy Reene
Advocatus Diaboli
 
Sy Reene's Avatar
 
Join Date: Feb 2015
Location: Wherever I am
Posts: 7,146

Bikes: Merlin Cyrene, Nashbar steel CX

Mentioned: 11 Post(s)
Tagged: 1 Thread(s)
Quoted: 3774 Post(s)
Liked 888 Times in 596 Posts
I never understood how, using examples above, measuring output for a 3 minute or so effort, can tell you what you could manage for a full hour.
Sy Reene is offline  
Old 09-05-20, 09:49 AM
  #8  
MoAlpha
ē ó
 
Join Date: Jun 2015
Location: Land of Pleasant Living
Posts: 8,436

Bikes: Shmikes

Mentioned: 53 Post(s)
Tagged: 0 Thread(s)
Quoted: 6559 Post(s)
Liked 3,057 Times in 1,669 Posts
Originally Posted by RChung View Post
Not any. For the Morton 3-param model you'll need at least 3 all-out efforts. You'll get slightly better (more robust) results if the all-out efforts are reasonably steady, though a nice thing is that they don't have to be slavishly steady. Also, the results will be slightly more robust if the shortest and longest efforts aren't too close together in duration, so maybe 3-4 minutes, 8-9 minutes, and maybe 16 or 17 minutes. The advantages of the CP/ W' model are that you get twice as many parameters to evaluate your condition than FTP, and you also get a way to assess the consistency of the tests.
Thanks. I keep meaning to read the paper, but my understanding of that model could be described politely as superficial. CP/Wí is completely new to me.
MoAlpha is offline  
Old 09-05-20, 09:50 AM
  #9  
MoAlpha
ē ó
 
Join Date: Jun 2015
Location: Land of Pleasant Living
Posts: 8,436

Bikes: Shmikes

Mentioned: 53 Post(s)
Tagged: 0 Thread(s)
Quoted: 6559 Post(s)
Liked 3,057 Times in 1,669 Posts
Originally Posted by Sy Reene View Post
I never understood how, using examples above, measuring output for a 3 minute or so effort, can tell you what you could manage for a full hour.
In my case, at least, itís pretty accurate.
MoAlpha is offline  
Old 09-05-20, 12:40 PM
  #10  
RChung
Senior Member
 
Join Date: Sep 2009
Posts: 1,818
Mentioned: 30 Post(s)
Tagged: 0 Thread(s)
Quoted: 514 Post(s)
Liked 469 Times in 185 Posts
Originally Posted by Sy Reene View Post
I never understood how, using examples above, measuring output for a 3 minute or so effort, can tell you what you could manage for a full hour.
It's not just a 3 minute effort. It's a couple of efforts of different durations. You may know that to define a line you need at least two points; to define a curve, you need at least 3, etc.

Here's an example, taken from my data. I haven't ridden outside since March, so these data points are taken from my indoor rides, but you can get an idea of what's happening. The top panel shows the "familiar" power-duration curve (for an old fat slow guy who hasn't been outside since March). The exact same data, but transformed from watts of power to Joules of work, are shown in the bottom panel. The thing to notice is that the data, when translated into Joules, is almost linear. (The correlation coefficient is 0.998). Since the data fit the regression line really really well, you can summarize these data pretty well with only two parameters: a slope, and an intercept. That's the basis for CP and W'. The slope of the regression line is in Joules/second, but a Joule per second is a watt -- so the slope is in watts. I haven't been riding much so the slope is really, really, low so please don't calculate it. In addition, the y-intercept is in kJ, and the intercept is called W'.

Notice also that the data being so linear make it easy to extend or project out to 3600 seconds ( = 1 hour). The nice thing is that you can see that at longer durations my average power decreases, so the data points are below the regression line. In fact, we have all the uusal regression diagnostics that tell us how well the data fit, and let us do estimates at various other durations I didn't test at. And, although there are around 10 points on that chart, you can sorta see that if I had only tested at around 3 minutes, 8 minutes, and 15 minutes, the points would still have been pretty close to the full line and pretty linear. So that's why we have some confidence that we can use data points at 3, 8, and 15 minutes to predict how much power I could put out for close to an hour. (Once I get much beyond a hour or so, my power drops off a lot -- but you can see that).

If your power were wildly inconsistent at different durations, you'd know that predicting out to an hour would be less reliable. You don't get that kind of insight from a single FTP test.

RChung is offline  
Likes For RChung:
Old 09-05-20, 03:43 PM
  #11  
Sy Reene
Advocatus Diaboli
 
Sy Reene's Avatar
 
Join Date: Feb 2015
Location: Wherever I am
Posts: 7,146

Bikes: Merlin Cyrene, Nashbar steel CX

Mentioned: 11 Post(s)
Tagged: 1 Thread(s)
Quoted: 3774 Post(s)
Liked 888 Times in 596 Posts
Originally Posted by RChung View Post
It's not just a 3 minute effort. It's a couple of efforts of different durations. You may know that to define a line you need at least two points; to define a curve, you need at least 3, etc.

Here's an example, taken from my data. I haven't ridden outside since March, so these data points are taken from my indoor rides, but you can get an idea of what's happening. The top panel shows the "familiar" power-duration curve (for an old fat slow guy who hasn't been outside since March). The exact same data, but transformed from watts of power to Joules of work, are shown in the bottom panel. The thing to notice is that the data, when translated into Joules, is almost linear. (The correlation coefficient is 0.998). Since the data fit the regression line really really well, you can summarize these data pretty well with only two parameters: a slope, and an intercept. That's the basis for CP and W'. The slope of the regression line is in Joules/second, but a Joule per second is a watt -- so the slope is in watts. I haven't been riding much so the slope is really, really, low so please don't calculate it. In addition, the y-intercept is in kJ, and the intercept is called W'.

Notice also that the data being so linear make it easy to extend or project out to 3600 seconds ( = 1 hour). The nice thing is that you can see that at longer durations my average power decreases, so the data points are below the regression line. In fact, we have all the uusal regression diagnostics that tell us how well the data fit, and let us do estimates at various other durations I didn't test at. And, although there are around 10 points on that chart, you can sorta see that if I had only tested at around 3 minutes, 8 minutes, and 15 minutes, the points would still have been pretty close to the full line and pretty linear. So that's why we have some confidence that we can use data points at 3, 8, and 15 minutes to predict how much power I could put out for close to an hour. (Once I get much beyond a hour or so, my power drops off a lot -- but you can see that).

If your power were wildly inconsistent at different durations, you'd know that predicting out to an hour would be less reliable. You don't get that kind of insight from a single FTP test.

I don't doubt this works, I just can't reconcile in my mind how small duration efforts could predict how well you'd do over time. Ie. Anaerobic vs aerobic ability, or muscle fatiguing or cramps
Sy Reene is offline  
Old 09-05-20, 04:22 PM
  #12  
asgelle
Senior Member
 
Join Date: Apr 2006
Location: Albuquerque, NM
Posts: 4,279
Mentioned: 11 Post(s)
Tagged: 0 Thread(s)
Quoted: 838 Post(s)
Liked 297 Times in 187 Posts
Originally Posted by Sy Reene View Post
I don't doubt this works, I just can't reconcile in my mind how small duration efforts could predict how well you'd do over time. Ie. Anaerobic vs aerobic ability, or muscle fatiguing or cramps
If you do a search on Monod 2 parameter model or some such, you can find much better information. The basic idea is that if we ignore very short term sprinting, the power to drive cycling (or any exercise) can conceptually be broken down into two parts: an aerobic component which can be maintained for a very long time and an anaerobic part, which like a battery, has a fixed amount of power that can be used to supplement the aerobic part. This anaerobic part can be delivered quickly or slowly. In the model, the rate isn't limited, just the total work done. So then if you do an all out effort of any duration, you'll be working the aerobic part to its max (this power is referred to as critical power or Cp) and completely drain the anaerobic part, call W'. So then total work performed for any duration will be Wt=Cp*t+W' and plotting Wt against t will give a straight line. Of course, the assumptions in the model break down at some point due to fatigue, which is why we look at and model a persons full power-duration curve to account for very short and very long efforts.
asgelle is offline  
Likes For asgelle:
Old 09-05-20, 04:49 PM
  #13  
RChung
Senior Member
 
Join Date: Sep 2009
Posts: 1,818
Mentioned: 30 Post(s)
Tagged: 0 Thread(s)
Quoted: 514 Post(s)
Liked 469 Times in 185 Posts
Originally Posted by Sy Reene View Post
I don't doubt this works, I just can't reconcile in my mind how small duration efforts could predict how well you'd do over time. Ie. Anaerobic vs aerobic ability, or muscle fatiguing or cramps
Right, read asgelle's response. Short duration efforts don't exactly predict how well you'd do over long durations, but they do influence what you'd do over long durations. Suppose you had a great sprint compared to one of your friends, and your left hand (short duration points) went up, but the two of you had essentially the same right hand (long duration) points. Then your slope would be slightly lower than your friend's, and it would mean that your FTP or CP would be slightly lower. OTOH, if your sprint was weak ass and sucked worse than his, but your endurance engine was good, the right hand points would pretty much stay where they are but the left hand points would be lower. So in order to produce the same number of Joules at longer durations, your slope would have to be slightly higher.

[Edited to add:] Looking at the data in work-duration terms is really a lot clearer. You can see whether your data are close to linear or not; and if not, where it starts to bend.

Last edited by RChung; 09-05-20 at 04:55 PM.
RChung is offline  
Old 09-08-20, 04:42 PM
  #14  
redsfan08
Junior Member
 
Join Date: Sep 2020
Posts: 13
Mentioned: 0 Post(s)
Tagged: 0 Thread(s)
Quoted: 6 Post(s)
Liked 0 Times in 0 Posts
Firstly do you have a power meter? If a long stretch of road or a long similar climb isnt available, can you do a ramp test?
redsfan08 is offline  

Posting Rules
You may not post new threads
You may not post replies
You may not post attachments
You may not edit your posts

BB code is On
Smilies are On
[IMG] code is On
HTML code is Off


Thread Tools
Search this Thread

Contact Us - Archive - Advertising - Cookie Policy - Privacy Statement - Terms of Service - Do Not Sell My Personal Information -

Copyright © 2021 MH Sub I, LLC dba Internet Brands. All rights reserved. Use of this site indicates your consent to the Terms of Use.