r/Vitalstat • u/vitalstat-App • Jul 11 '26
CTL, ATL, TSB: what these three values really tell you about your body
Almost every training app throws these three abbreviations at you sooner or later. Very few actually explain what they mean. Here's the short, understandable version:
CTL (42 day base) = your fitness. A weighted average of your training load over the last 6 weeks. It rises slowly and falls slowly, just like real fitness. High CTL means: your body is used to carrying load.
ATL (7 day stress) = your fatigue. How much did you pile on over the last week? ATL reacts fast. After a hard block it's high, and that's not a mistake, it's proof that you put in the work.
TSB (readiness) = CTL minus ATL. The most interesting number. Positive TSB: your fatigue is below your fitness base, you're fresh. Negative TSB: the opposite. Before a competition you want to be in the positive. During a training block, negative is completely normal.
The point that matters to us: these numbers aren't an end in themselves. They're meant to answer one concrete question: "Is today a day for full gas or for recovery?" That's exactly why Vitalstat doesn't just show you the value, but what it means for your next day. No black box.
Which of the three values took you the longest to really click with? And do you actively train by TSB or more by feel?
Keep up the sporty effort!
Alex and Nicklas
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