IF : Intensity Factor
LoadYour session NP divided by your FTP : a unitless ratio from 0 to ~1.1.
IF answers: "what fraction of my threshold did I ride at?". IF = 0.70 → easy endurance. IF = 0.85 → sustained sweet spot. IF = 0.95-1.00 → threshold work. IF > 1.05 over an hour = an FTP retest in disguise.
In TriPaced:
TriPaced displays the target IF of every session. It's more telling than the zone alone: a long Z2 sits at IF=0.65, a short threshold piece at IF=0.95. You can see at a glance if a session is hard or recovery.