TSS /IF : what's the point?

Hey guys,
Could someone explain the benefit of TSS®/IF® ?
I understand the TSS, the IF but not the relationship between the two. Probably my bad side in math :slight_smile:

TSS is actually “derived” from IF :slight_smile:

From here,

TSS = (sec x NP x IF)/(FTP x 3600) x 100



and where NP is a “complex” math around power, you can simply think about it as “adjusted average power”.

IF is meant to tell you how hard you’ve been riding (the closer you get to 1, the closer you are to having ridden at your FTP); 0.7 should fee “easy”, while you won’t probably last 40 minutes at 1.1 :slight_smile:

TSS is meant to tell you how much “stress” you’ve accrued throughout the workout duration (riding at 0.5 IF for 30 hours is going to be quite a bit of stress, but you might get the same amount of stress in a shorter amount of time, riding at a higher IF).


Thanks A LOT for taking time to explain.

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@Frederic_BATTIE You might find it easier to see the relationships like this:
TSS per hour = 100 x IF squared.

This is the same formula that @Giacomo_Rizzo used.

So, if IF = 0.7, then IF squared is ~ 0.5, so 50 TSS per hour.
IF = 0.8 means 64 TSS per hour
IF = 0.9 means 81 TSS per hour
IF = 1 means 100 TSS per hour.

One additional note.

When TSS is a high priority key metric in one’s training ecosystem, I suggest that the intensity metric to use should be precisely TSS/hour because it gives a linear relationship to other TSS based variables like total TSS, CTL and ATL.


Thanks a lots for your tought guys. You’re Awesome

IF= % of your FTP

Intensity Factor = Normalised Power / Threshold Power

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