Chronic Training Load (CTL)

CTL (Chronic Training Load), called "fitness" in many apps, is a slow-moving measure of the training load you have built up over the past weeks. The number rises with consistent training and gradually fades when you do less.

In Trimetra this is called fitness.

What is CTL?

In the common models, CTL is a weighted average of your daily load scores (such as TSS) over roughly the past six weeks, with recent days counting a little heavier. One hard day changes it little; weeks of consistent training change it much more. That makes CTL above all a measure of consistency and support: how much load your body is used to.

What CTL is not: a direct measurement of your aerobic capacity, health or race level. Two athletes with the same CTL can differ sharply in speed — and you can get fitter while your CTL stays the same, for example by training smarter rather than more.

How do you build CTL up sensibly?

The pitfall is the rate of build-up. Because CTL moves slowly, it is tempting to push it up with a couple of monster weeks — exactly the pattern that coincides with overload and injury. A gradual, sustained build-up with recovery weeks built in yields a higher and steadier base over time than peaking and crashing.

So don’t look only at the level of your CTL, but at the slope: how fast is it rising, and can your body take it? The ratio between your recent and built-up load (ACWR) is a useful extra signal for that.

How Trimetra personalises this

Trimetra tracks your load build-up against your own history rather than a universal rule: the planner weighs how fast your base is rising, how your recovery signals and niggles respond to it, and becomes more cautious with extra quality when the build-up gets too steep. Structural changes to your plan appear as a suggestion, not a quiet adjustment.

Frequently asked questions

What is a good CTL?

There is no universal number. CTL measures how much load your body is used to, and two athletes with the same CTL can differ widely in speed. Only compare the number with your own history, and focus on a gradual, sustained build-up.

How fast can you build your CTL?

Slower than the temptation suggests: pushing CTL up with a few monster weeks is exactly the pattern that coincides with overload and injuries. A gradual build with recovery weeks built in delivers a higher and more stable base in the long run.

Does your fitness drop immediately if you take a week off?

No. CTL moves slowly: one easy or free week costs little of your built-up base, and recovery weeks are part of a good build. Only weeks to months of training less really lowers the base.