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TRAINING LOAD CALCULATOR

Daily TSS in. CTL, ATL, and TSB out. See where you sit on the fitness-fatigue curve.

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METHODOLOGY

The impulse-response model: Banister and colleagues introduced the fitness-fatigue framework in the 1970s. Every training session produces two competing responses — a slow-building fitness gain and a fast-peaking fatigue cost. Performance at any point is the difference between accumulated fitness and accumulated fatigue. That difference is what we call form, or TSB.

CTL (Chronic Training Load): A 42-day exponentially weighted moving average of daily TSS. It represents your accumulated fitness — the body of work you have done over the past several weeks. CTL rises slowly and decays slowly, which is why consistent training matters more than any single session. The formula: CTLtoday = CTLyesterday + (TSStoday − CTLyesterday) × (1/42).

ATL (Acute Training Load): A 7-day exponentially weighted moving average of daily TSS. It represents recent fatigue — how hard the last week has been. ATL responds quickly: a single big day can push it well above CTL, and a few rest days bring it back down fast. ATLtoday = ATLyesterday + (TSStoday − ATLyesterday) × (1/7).

TSB (Training Stress Balance): Simply CTL minus ATL. When ATL exceeds CTL, TSB is negative — you are carrying fatigue and your performance is suppressed. When ATL drops below CTL (typically during a taper), TSB goes positive — stored fitness is expressing itself, and you are in race-ready form.

Coggan, Allen, and TrainingPeaks:Dr. Andrew Coggan and Hunter Allen adapted Banister's model for cycling with power data, and TrainingPeaks built the Performance Management Chart (PMC) that popularised CTL, ATL, and TSB as the standard training-load vocabulary. The PMC remains one of the most useful single views in endurance coaching.

Limitations: The 42-day and 7-day time constants are population averages — your personal response curve may differ, particularly if you are a masters rider or have a long endurance background. TSB treats all TSS equally: 100 TSS from a Zone 2 ride and 100 TSS from VO2max intervals carry identical weight in the model, even though the recovery demand is very different. The model also ignores life stress, sleep quality, and illness — all of which affect real-world readiness. Use TSB as a trend indicator, not as a single number to race off.

Last updated: July 2026 · Tool version 1.0

FROM HERE

ARTICLEManaging Training Load in Your 40s and 50sAfter 40, the limiter usually isn't the training — it's how much load you can absorb. Managing that load deliberately, with simple monitoring, is what separates riders who keep improving from riders who keep breaking down. Here's how to track it and act on it.PODCASTStrength Training For Cycling Simplified | Derek Teelwith Derek TeelARTICLEHow to Read Your Training Data: TSS, CTL, ATL, and TSB Without the JargonMost amateur cyclists have a TrainingPeaks account they barely read. The numbers there — TSS, CTL, ATL, TSB — are not as complicated as they look. Here's the field guide for reading them properly, and the three signals worth acting on.ARTICLEHow to Use Training Load Without Overthinking ItThe Performance Management Chart is a tool, not a coach. Here is how to use training load numbers without letting them use you.

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