Sometimes I dont understand Training Peaks

Today I did a Zwift race and warmup, 152 TSS total…my fitness went up 1 point. Then I go to the gym for 8o minutes and get a two point increase. Seems like the Fitness number rises ever so slowly but drops so quick if you take one rest day.

TSS is designed for cycling, using it for anything else is a mistake imo.

There is a built in decay, the higher your CTL the quicker it will drop in absolute numbers.


That is because of how averages work.

Think about back in school and your GPA. If you had a high GPA, even a 4.0 grade would not raise your GPA much….but if you failed a class, a 0 could crush it.

Now substitute CTL / Fitness for GPA. If you have a CTL of ~80, it is going to take a pretty high number above 80 to move it, but a day off (0 TSS) is so far below your average that it will have a larger impact.


I’ve always thought that CTL numbers were not very representative of how I actually feel. You dont lose that much fitness taking a rest day…maybe its time to ditch TP.

What cardio did you do in the gym? Was it cycling specific?

I’ve NEVER been told that CTL should be representative of how I feel. However after an off-season and during base the progressive rebuilding of volume will start to drag me down coming into a recovery week.

Like any tool it helps if you understand how to use it. Terms like fatigue, fitness, and form are confusing, and distort how the chart is meant to be used.

The idea is you are applying training impulses, organized into cycles. There is some science behind this human performance model, but it’s often ignored.

During some parts of the season the goal is to progressively increase cumulative training load (CTL). During other parts of the season that is NOT the goal.

Focusing on “fitness went up 1 point, then after then gym it went up 2 points” is missing the forest for the trees IMHO.

Go back to the forest… Here is an example plan from base to peak for a road race. Total of 32 weeks:

Volume and CTL progressively build during 16 weeks of base, but then is “drawn down” after switching to higher intensity work to prepare to peak for an event at the end of that timeframe.

1 Like

Thats because CTL is not fitness, its chronic training load. Yeah yeah yeah, TP calls it fitness, but thats not what the people in the know think it is.


It’s not adding “fitness” or ctl from a single event, it’s from the combined tss of the day and comparing it to the last 42 days.

Make sure your heart rate zones are appropriately configured or it’ll over inflate your tss when using hrtss.

I track gym work, running, swimming, and biking with tss. If the zones are properly configured it can be another powerful metric on analyzing progress and fatigue. But like any tool, the output data is only as good as the data you are giving it. And you also have to understand what data is going into those numbers, how it’s calculated, and how you should use it.