These parameters are used in workouts and the summary of the rest of the sessions.
IF. Intensity factor
It is the ratio between the normalized power of a session and your current FTP level.
For example, if your FTP test is 270W and in a one-hour session you have performed 270W of normalized power, the Intensity Factor is 1.0.
TSS Training Stress Score
This parameter takes into account both the previous Intensity Factor and the duration of the session and is an estimation of the wear during it.
The TSS can also be used as an indicator of the recovery time required before the next session.
The approximate scale of the relationship between the TSS of a session and the necessary recovery time:
TSS less than 150 - Low. Recovery in 24 hours.
TSS from 150 to 300 - Medium. Recovery between 1 and 2 days.
TSS from 300 to 450 - High. Recovery in 2 days plus.
TSS greater than 450 - Very high. High fatigue, recovery in several days.