CTL (fitness), ATL (fatigue), and TSB (form) are rolling averages of your daily Training Stress Score. Together they show whether you are building fitness, accumulating fatigue, or arriving at a race fresh and ready.
Who this is for
Athletes using TrainingPeaks, Intervals.icu, or similar platforms who want to interpret their performance management chart (PMC).
The three metrics
CTL (Chronic Training Load): 42-day rolling average of daily TSS. Represents fitness — higher CTL generally means better endurance capacity.
ATL (Acute Training Load): 7-day rolling average of daily TSS. Represents fatigue — spikes when you train hard recently.
TSB (Training Stress Balance): CTL minus ATL. Positive TSB means relatively fresh; negative means fatigued.
Reading the numbers
| TSB range | Typical meaning |
|---|---|
| +10 to +25 | Fresh — good for racing or testing |
| -10 to -30 | Productive training load — building fitness |
| Below -30 | High fatigue — injury risk increases |
| Above +25 | Detraining — fitness may be fading |
Race-day targeting
Many coaches aim for TSB between +5 and +20 on race day, achieved by reducing volume in the taper while maintaining short intensity touches.
Exact optimal TSB varies by athlete and event distance.
Common mistakes
- Chasing high CTL without recovery — fitness and fatigue rise together.
- Ignoring TSB and racing deeply fatigued.
- Obsessing over daily TSS instead of weekly patterns.
Sources
Using Vo2Max
Vo2Max Pro includes load analytics (ATL/CTL/TSB) when you sync activities — so you can see fitness trends alongside your periodized plan.