In order to accurately measure your Functional Threshold Power (FTP), Zwift provides you with two different versions of the FTP test:
- The full FTP test - 73 minutes total
- An abbreviated FTP test (same test interval with shorter warmup and cooldown) - 45 minutes total
During both of the FTP tests, you'll do warm up intervals before riding at a challenging effort level for 20 minutes and finishing with a cooldown block. Both tests take 95% of the average power exerted during the 20 minute test block. At the end of the test, Zwift will display the option to update the FTP value on your profile with the one from the test.
Taking the FTP Test with a Smart Trainer
If you're on a smart trainer and use ERG mode during the 20 minute FTP test block, you will need to change bike gears to get an appropriate resistance level.
Unlike most workout blocks with ERG mode, Zwift will not change resistance to match a power target during the FTP test block. The idea behind the test is that you put out the most wattage you can over that 20 minute time period, so trainer resistance is set at a neutral level, allowing you to shift to the resistance level that best matches your desired cadence and wattage.