Originally Posted by
atwl77
FTP is useful for structured interval training, like in Trainerroad or Sufferfest, because the intensity of the workouts will be based on that number.
The actual process of doing FTP tests is also useful for time-trailling, as it helps you learn to pace yourself over long durations.
If you're serious about improving your fitness or just getting quicker on the bike, FTP training is incredibly useful. It totally changed the way I look and feel about riding my bike. I hardly use it when I'm riding outside but for the trainer it's invaluable.