Training Stress Score Math

Training
1

Ok I found this on Trainer Road but I can’t find anything more than this :

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

…where

  • “sec” is duration of the workout in seconds,
  • “NP” is Normalized Power® (don’t worry about this for now),
  • “IF” is Intensity Factor® (a percentage of your FTP; in other words how intense the effort was),
  • “FTP” is Functional Threshold Power (your best average power for a one-hour race or test),
  • and “3600” is the number of seconds in an hour.

Let’s take this workout as an example :

sec = 1 x 60 x 60 + 11 x 60 + 25 = 4,285
NP = ?
IF = ? is this Wtd Avg Power / FTP? so 175 / 227 = 75%?
FTP = 227
3600

TSS = (4,285 x ? x 75%?)/(227 x 3600) x 100

72 (from my intervals site) = (3213.75 x NP) / (817200) x 100

0.72 = (3213.75 x NP) / (817200)
588384 = 3213.75 x NP
183 = NP

I’m still not sure what NP and IF are supposed to be - can someone help me out?

2

Are you looking for the math for calculating NP and IF? If so this might help…

3

rolling_average = 30 second rolling average

rolling_avg_powered = rolling_average^4

avg_powered_values = average of rolling_avg_powered

NP = avg_powered_values^0.25

gulp…that is some serious math…

useful link : Cycling Training: Easily Understand Normalized Power in 4 Steps - JayLo Cycling and Adventures

so I wonder in practice how different is normalized power from average watts and under what circumstances would they be materially different

4

Normalized Power is a registered trademark of Peaksware, the company that owns TrainingPeaks. So best to read their description of NP:

For more information on NP, view the TrainingPeaks website.

Normalized Power (NP), Intensity Factor (IF), and Training Stress Score (TSS) are registered trademarks of Peaksware, LLC.

5

They differ for rides with hard efforts. The calculation makes those “stand out”.

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