Performance manager charts, training loads, stress, form……

Part 1 of many…..

Training platforms have a way to objectively define training load, or training stress, generally indicated by TSS (Training Stress score).

As you can imagine, the different platforms have different ways to measure this, which for the purposes of this article aren’t important, we will delve into some of the complexities in upcoming articles, talks and discussions, for this article we focus on TSS calculations:

  1. Cycling (sorry for the runners and swimmers!)
  2. Power based TSS calculations

To calculate TSS we look at the intensity and duration of the workout, TrainingPeaks uses the following formula to quantify this:

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

  • Sec is the duration of the ride in seconds,
  • NP is the normalized (not average) power for the ride,
  • FTP is your Functional Threshold power or the power you can sustain for 1 hour, typically calculated as 95% of a 20 minute effort,
  • IF is the intensity factor of the ride (calculated from NP as a % of your FTP),

Fortunately, we don’t need to whip out our calculators and calculate this manually, all the data and formulas are already programmed into TrainingPeaks.

Using this TSS we get an objective measure of how much training stress we experience every day.

So how does that help us?  If we expanding on this Daily TSS, a Chronic Training Load (CTL) is a weighted calculation of TSS scores over the previous 6 weeks (42 days).

This would equate to indicating a persons historical ‘exposure’ to a training load over the past 42 days, the higher the daily TSS, and the more regular the frequency of the rides, the higher the CTL is likely to be.

The CTL figure, and even TSS, are not percentages, but an objective measure of a persons ability to train.  TrainingPeaks refers to CTL as fitness, ie the higher your CTL, the fitter you are likely to be, or more precisely, the more training stress you have experienced in the last 6 weeks.

Now that’s clear, we head onto Acute Training Load (ATL) which also uses this useful TSS number but looks at only the last 7 days, i.e. what training stress has a person experienced in the last 7 days.

So how is ATL useful?  Well, if a person has been training consistently for 42 days and has a CTL of 75, but then decides to increase the daily TSS of his rides by either increasing the duration, or the intensity, or both, the TSS should rise, indicating a higher daily TSS for the last 7 days (ATL) which may be 90.  This would indicate the person has trained harder in the last 7 days, than they are used to, and will likely be feeling some fatigue and require recovery to adapt to the higher training loads experienced in the last 7 days.

The way to objectively quantity this feeling of fatigue, is with a number, of course, called Form or TSB (Training Stress Balance) which is calculated simply by subtracting one from the other:


  • If TSB is negative, i.e. ATL is higher than CTL, the person has negative form, and has done more in the last 7 days than they have in the last 42 days.
  • If the form or TSB is positive, i.e. the person has done less in the last 7 days than they have in the last 42 days, they will feel fresher, or ready to race, or train, or beat you mates on the ‘chilled’ Sunday Coffee ride.

Leave a Reply

Your email address will not be published. Required fields are marked *