Acute Training Load (ATL)
Acute Training Load (ATL) reflects recent training load and helps estimate short-term fatigue in a training load management system.
Acute Training Load (ATL)
You can think of Acute Training Load (ATL) as a fast-moving average of how hard you’ve trained recently. It’s commonly calculated over roughly 7 days, so it reacts quickly to your most recent workouts.
Example card: values and percentages are for UI preview only. Interpret them with your own data and trends.
Core Concepts
- Highly responsive: ATL reacts strongly to single sessions. A high-load day (e.g., TSS 300) can make ATL jump 30–40 points the next day.
- Dissipates quickly: with a 7-day time constant, fatigue rises and falls fast. Stop training for 3–5 days and ATL drops sharply. This is the physiological basis of tapering.
- Subjective experience varies: ATL is a mathematical model. At the same ATL, you may feel more tired due to poor sleep, stress, or nutrition; or feel fine when freshness is high. Don’t rely on numbers alone—combine with RPE.
- Exponential decay: “7 days” is not a simple 7-day average. Recent training has much higher weight, and older training decays exponentially.
How to Interpret and Use
- ATL rising fast: usually means your load has increased quickly. If intensity or volume spikes for several days, prioritize recovery (sleep, nutrition, pain/injury signals).
- ATL falling fast: usually means training volume dropped or you entered a taper. You may feel fresher short-term, but staying too low for too long can reduce fitness.
- Use with CTL/TSB: ATL alone is easy to misread. Pair it with Fitness | Chronic Training Load (CTL) and Form | Training Stress Balance (TSB) to interpret trends and ranges.
How Trainingload.ai uses ATL
Trainingload.ai uses ATL as a short-term fatigue signal. A sudden ATL rise can trigger a closer review of upcoming hard sessions, especially after missed recovery, stacked intensity, or unusually long workouts.
ATL does not automatically mean “stop training”. In a build block, some fatigue is expected. The useful question is: is this fatigue intentional, recoverable, and aligned with the plan?
Calculation Formula
ATL is an exponentially weighted moving average (EWMA) of daily training load (TSS or TRIMP). In the classic PMC (Performance Manager Chart) framework, ATL typically uses a short time constant (commonly 7 days) to represent short-term fatigue:
- : today’s TSS or TRIMP.
- : the time constant (about one week). Yesterday’s training carries much more weight than training from two weeks ago.
The ATL vs. CTL Dynamic
ATL and CTL are complementary trend signals in the PMC:
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Improving fitness (CTL ↑) usually requires creating some short-term fatigue (ATL ↑).
- During a build block, ATL often sits above CTL.
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Showing form (TSB ↑) usually requires reducing short-term fatigue (ATL ↓).
- During a recovery week or pre-race taper, ATL drops much faster than CTL, revealing fitness.
Trainingload.ai note: for runners, ATL spikes can be riskier than for cyclists. Running creates not only metabolic fatigue (captured by TSS) but also substantial musculoskeletal damage. In high-ATL running weeks, pay extra attention to pain feedback and injury signals.
References
Chronic Training Load (CTL)
Chronic Training Load (CTL) reflects longer-term average training load and helps interpret fitness trends inside a training load management system.
Training Stress Balance (TSB)
Training Stress Balance (TSB) is derived from CTL and ATL and helps estimate freshness, fatigue, and readiness within a training load system.