Tom, the VO2 number isn't really used in the FTP calculation. The standard calculation for VO2 is 1.2 times your FTP value. If your tested VO2 is greater than or less than what is calculated it indicates a disparity or a hole in your fitness and power generation. In that case use the 1.2 times your FTP result for the VO2 training. The short and simplified answer to why there is a 5min VO2 in the test is really just to wear you out enough for the 20min FTP test so that it will simulate a full 1 hour FTP test after the subtraction of 5% of the measured FTP value. This comes out to provide a vary close approximation of a full 1 hour test without having to do all the work.
The wiki has a more detailed explanation, plus there are lots of threads in the forums on this topic..
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Tom, the VO2 number isn't really used in the FTP calculation. The standard calculation for VO2 is 1.2 times your FTP value. If your tested VO2 is greater than or less than what is calculated it indicates a disparity or a hole in your fitness and power generation. In that case use the 1.2 times your FTP result for the VO2 training. The short and simplified answer to why there is a 5min VO2 in the test is really just to wear you out enough for the 20min FTP test so that it will simulate a full 1 hour FTP test after the subtraction of 5% of the measured FTP value. This comes out to provide a vary close approximation of a full 1 hour test without having to do all the work.
The wiki has a more detailed explanation, plus there are lots of threads in the forums on this topic..
http://members.endurancenation.us/R...r+Athletes
You can read more on the wiki under bike testing..
http://members.endurancenation.us/R...fault.aspx