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

TSS is actually “derived” from IF

From here,

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

where

```
IF = NP / FTP
```

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

TL;DR:

**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

**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.

@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