The Power Speed Profile Aerobic Assessment is used to assess your medium and long critical period power.There are a few important things to understand. During the test, you're going to ride two all-out efforts, 4 minutes and 20 minutes in duration. You will need to keep going as hard as you can for the entire duration of both tests. Pacing is important in these tests and covered in the audio.That’s it. Ridewell.Note: If you don’t want to go on RPE, have your computer set to display % of FTP for warm up and recovery.