# CP vs FTP

mclarent
Posts:

**784**
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.

"And the Lord said unto Cain, 'where is Abel thy brother?' And he said, 'I know not: I dropped him on the climb up to the motorway bridge'."

- eccolafilosofiadelpedale

- eccolafilosofiadelpedale

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## Posts

2,8101,780CP20 (20mins) isn't - most people can do quite a bit more than FTP for 20 mins. (+5% or higher usually)

"Because the cycling is pain. The cycling is soul crushing pain."

4,1614,161The 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.

1,246How 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?

79,667i.e. CP60=power for 60 minutes

CP6 is power for 6 mins...

1,951It 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.

1,951Here is a calculator. You should be able to follow the fomulas as it's an excel spreadsheet.

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

4,161Friel 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.

4,161It 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

4,1614,9274,1614,927784Thanks 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?

- eccolafilosofiadelpedale