ATL — Acute Training Load
ATL is the faster-moving average of daily cardiovascular TRIMP load.
The exact seven-day recurrence
For local day d, L[d] is the sum of calculable activity TRIMP on that start date.
ATL[d] = ATL[d−1] + (L[d] − ATL[d−1]) / 7The coefficient is 1/7. Seven days is the smoothing time constant, not a seven-day arithmetic average or a hard cutoff: older values continue to contribute with decreasing weight. Its scale is TRIMP per day. The initial state is zero at the beginning of the available activity history.
Verified example
With previous ATL 60 and today’s load 100 TRIMP, ATL becomes 65.714286. A rest day from ATL 60 instead gives 51.428571. This distinguishes an exponential recurrence from simply summing the latest seven entries.
Limits and related values
A day without recorded work contributes zero. An activity whose TRIMP is unavailable can leave the day’s sum incomplete; unimported history cannot be recovered by smoothing. The first 41 days carry the shared low-confidence flag. Threshold changes and imported older history can change the inputs after recalculation. Read the common time and missing-data rules.
CTL uses the same TRIMP series with coefficient 1/42. TSB uses yesterday’s CTL minus yesterday’s ATL. The UI’s Fatigue name describes this model value, not a measurement of your current fatigue.
Sources and implementation scope
Morton, Fitz-Clarke and Banister (1990), impulse-response performance modeling provides background, not a specification of every EffortSignal rule. The formulas, windows, quality gates and examples above describe EffortSignal 0.1.13, checked September 10, 2026. Product-specific thresholds and rounding should not be attributed to the background source.
Content checked September 10, 2026 · EffortSignal release 0.1.13