CP vs FTP

mclarent

Hi all - just a quick one really, is CP as near as dammit FTP? Just bought a flow and want to know (innit bro). :shock: Sorry.

jibberjim

Yes.

nmcgann

CP60 - i.e. the best power you can do for 60mins would be the same as FTP.

CP20 (20mins) isn't - most people can do quite a bit more than FTP for 20 mins. (+5% or higher usually)

Alex_Simmons/RST

nmcgann wrote:

CP60 - i.e. the best power you can do for 60mins would be the same as FTP.

CP20 (20mins) isn't - most people can do quite a bit more than FTP for 20 mins. (+5% or higher usually)

There is only one Critical Power.

Alex_Simmons/RST

The Critical Power (CP) paradigm describes the work-time relationship, where the work performed during a maximal bout of exercise is dependent on the duration of effort and the individual’s current aerobic and anaerobic capabilities. i.e. a higher work rate (power) is possible over shorter durations and vice versa.

The work-time relationship is readily expressed as a linear equation:

Workmax = AWC + (CP x t)

Workmax is the total work performed (in joules)
AWC is the anaerobic work capacity (y axis intercept – joules)
CP is the Critical Power (slope of the line – watts)
t is time (x axis – seconds)

In this sense CP is the maximal power output sustainable over a long time without fatiguing. In practical terms CP corresponds closely to FTP.

It is possible (indeed useful) to use this relationship to establish both a rider’s CP and AWC and can be readily done via measuring the average power of two or more maximal exercise bouts over different durations between 3 and 30 minutes.

The CP paradigm can also be used to pre-determine/estimate a rider’s maximal power output over various untested durations, as well as establish changes in both AWC and CP resulting from training.

chrisw12

:? :? :? :? :?

How is work done vs time LINEAR?

Surely it's a decay curve flattening out as time increases or am I getting confused with a power vs time curve? Or are they the same thing?

Anonymous

I thought critical power was the phrase used by Joe Friel to describe your best power output for a particular length of time...

i.e. CP60=power for 60 minutes
CP6 is power for 6 mins...

doyler78

NapoleonD wrote:

I thought critical power was the phrase used by Joe Friel to describe your best power output for a particular length of time...

i.e. CP60=power for 60 minutes
CP6 is power for 6 mins...

It is however Friel misappropiated the term which had already existed for many years. Monod & Scherer (sp?) came up with this name first and it is their model that Alex refers to. Whilst is is unfortunate that Friel used the term it nevertheless now probably has more people who understand his interpretation than do the originators.

doyler78

chrisw12 wrote:

:? :? :? :? :?

How is work done vs time LINEAR?

Surely it's a decay curve flattening out as time increases or am I getting confused with a power vs time curve? Or are they the same thing?

Here is a calculator. You should be able to follow the fomulas as it's an excel spreadsheet.

http://velo-fit.com/new/tools.php

Alex_Simmons/RST

doyler78 wrote:

NapoleonD wrote:

I thought critical power was the phrase used by Joe Friel to describe your best power output for a particular length of time...

i.e. CP60=power for 60 minutes
CP6 is power for 6 mins...

It is however Friel misappropiated the term which had already existed for many years. Monod & Scherer (sp?) came up with this name first and it is their model that Alex refers to. Whilst is is unfortunate that Friel used the term it nevertheless now probably has more people who understand his interpretation than do the originators.

Correct. CP has a precise meaning in exercise physiology and has existed for a good 50 or more years.

Friel took the term and made something else up that was semi related, confusing matters somewhat.

Mean Maximal Power for a given duration would have been better.

Alex_Simmons/RST

chrisw12 wrote:

:? :? :? :? :?

How is work done vs time LINEAR?

Surely it's a decay curve flattening out as time increases or am I getting confused with a power vs time curve? Or are they the same thing?

It's the work-time relationship, not power-time.

It is, for durations between a few minutes and about an hour, remarkably linear. And it is for that reason, one of the better methods of estimating Functional Threshold Power (provided you test correctly).

Refer Sin #5 here:
http://alex-cycle.blogspot.com/2008/05/ ... -sins.html

and Sin of Sins #8 here for what to avoid doing when testing for and calculating CP:
http://alex-cycle.blogspot.com/2009/07/ ... ftp-2.html

Alex_Simmons/RST

mclarent wrote:

Hi all - just a quick one really, is CP as near as dammit FTP? Just bought a flow and want to know (innit bro). :shock: Sorry.

Ap[art from testing properly and using the data appropriately, it also very much depends on the accuracy of your Flow. If it isn't accurate or has a non-linear slope in reported power (compared to actual), then the CP model (or any testing) will succumb to GIGO and report an incorrect CP and AWC.

Bronzie

Alex_Simmons/RST wrote:

the CP model will succumb to GIGO

an acronym too far - what is GIGO?

Alex_Simmons/RST

garbage in, garbage out

Bronzie

still taking the pith I see

mclarent

Alex_Simmons/RST wrote:

mclarent wrote:

Hi all - just a quick one really, is CP as near as dammit FTP? Just bought a flow and want to know (innit bro). :shock: Sorry.

Ap[art from testing properly and using the data appropriately, it also very much depends on the accuracy of your Flow. If it isn't accurate or has a non-linear slope in reported power (compared to actual), then the CP model (or any testing) will succumb to GIGO and report an incorrect CP and AWC.

Thanks Alex, and everyone else. One followup if I may? I'm assuming the flow will be incorrect in absolute terms, as it's a bit old,
but was assuming that as long as it was calibrated and applied consistently that this didn't really matter. However a non-linear slope in reported power sounds pretty terminal. Is there any way of ascertaining this short of checking vs a powertap or similar? I can't get the data out currently as i only have the basic headunit. Or how about if I can find someone with the appropriate headunit?