# Learn

Canonical HTML: https://effortsignal.com/learn/

Last content update: 2026-09-10

Understand the values behind your training. Each explanation documents the calculation used by EffortSignal, a worked example and the data it needs.

- [Activity Metrics: Work, Efficiency and Intensity Minutes](/learn/activity-metrics/): Understand mechanical work, output per heartbeat, relative heart rate and intensity-minute credit.
- [Aerobic Decoupling](/learn/aerobic-decoupling/): Aerobic decoupling compares output per heartbeat in the first and second halves of suitable recordings.
- [ATL — Acute Training Load](/learn/atl/): ATL is the faster-moving average of daily cardiovascular TRIMP load.
- [CTL — Chronic Training Load](/learn/ctl/): CTL is the slower-moving average of daily cardiovascular TRIMP load, shown as Fitness.
- [Next-day Easy-load Estimate](/learn/easy-trimp/): The easy-load estimate solves the product's ATL and CTL recurrences for an equal next updated state.
- [Estimated FTP from Cycling Power](/learn/eftp/): eFTP is a constrained estimate from cycling power-duration evidence, separate from the configured FTP.
- [Training Monotony and Training Strain](/learn/monotony-strain/): These Dashboard summaries describe the distribution and amount of TRIMP over seven consecutive daily rows.
- [Planned Workout Load](/learn/planned-load/): Planned load estimates the authored structure. It does not run the completed-activity sensor formulas in advance.
- [Power Intensity](/learn/power-intensity/): Power Intensity expresses Weighted Power relative to the applicable power threshold.
- [Power Variability](/learn/power-variability/): Power Variability compares Weighted Power with average timer-running power.
- [PSS — Power Stress Score](/learn/pss/): PSS combines timer duration with weighted power relative to the applicable FTP.
- [Readiness: Factors, Baselines and Coverage](/learn/readiness/): Readiness combines baseline-relative HRV, resting heart rate, sleep and workload. It is a model with explicit missing-data gates.
- [How Training Load Works](/learn/training-load/): Follow the exact path from recorded heart rate to daily TRIMP, ATL, CTL and TSB.
- [TRIMP — Training Impulse](/learn/trimp/): TRIMP estimates cardiovascular training load from duration and relative heart rate.
- [TSB — Training Stress Balance](/learn/tsb/): TSB, shown as Form, is the difference between chronic and acute load entering a day.
- [Your Usual Training Volume](/learn/usual-volume/): The weekly usual range compares a completed week with eight immediately preceding complete weeks.
- [Weighted Power](/learn/weighted-power/): Weighted Power gives variable power a fourth-power-weighted summary over complete 30-second windows.
- [Workload Ratio](/learn/workload-ratio/): The Dashboard workload ratio compares the current ATL with CTL from the same TRIMP history.
- [Training Zones and Effective Thresholds](/learn/zones/): Zones classify measured output or heart rate using the athlete settings applicable to the activity.