First, we need to know what FTP is. FTP stands for Functional Threshold Power. This is something that an academic researcher developed in Texas. This was not developed by a pro team’s coach. FTP is the power that you can produce for one hour within an aerobic capacity. You don’t necessarily have the ability to sustain this power for 2 hours. You can produce this power for 1 hour without any interruption.
How do we typically set FTP? We listen to folks with training programs. They have us take a test for 20 minutes and multiple the power by 95%. This does not work. Zwift does the same thing.
Were you riding through a big climb in Zwift and it lasted for 20 minutes? You set a new power record. Your heart rate was 180bpm. Perhaps you only spun the cranks at 55rpm. Was this not anaerobic? Zwift applied the 95 percentage against your new power record and displayed a window. Within the window it stated that your FTP increased. Can we rely upon this display?
Well not quite. Your heart rate was 180. Was this aerobic? No.
The best way to determine your FTP and your actual zones is to complete the 1 hour test. You might want to rest for two days to ensure full recovery prior to completing the FTP test.
warm-up for 20 minutes; ride for 1 hour.
While you are pedaling for the 1 hour, try to reach a heart rate in the 150 to 165 range. Hold your efforts while you maintain this heart beat. Pick flat terrain for this effort. Try to avoid stop lights and other traffic control devices. Pick a route with long sections that do not require stopping.
It takes practice to maintain that smooth pace and produce the power for an hour. If you don’t feel that you succeeded on the first try, then repeat the process on another day.
When you finished pedaling the second section, use the average power of the second section as your FTP.