Originally Posted by
surak
I've done TR and Zwift ramp tests, the Sufferfest 4DP test, and had Garmin autocalculate FTP. The Garmin estimate, as far as I can tell, just took my best 20 min avg power during a longer ride, so I consider it much more arbitrary.
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I think Coggen in his book talks about using a riders best 20 minute average during a ride to determine ftp. The most important thing is to use the same system consistently. Eventually a rider will figure out what they have to do to get their best numbers.