# Training Zones and Effective Thresholds

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

Last content update: 2026-09-10

Zones classify measured output or heart rate using the athlete settings applicable to the activity.

## Boundaries and inputs

Power zone boundaries convert configured percentages to watts:

```text
watts boundary = effective FTP × percent / 100
```

A sample belongs to the zone whose lower bound is inclusive and upper bound is exclusive; an open-ended final zone has no upper bound. Heart-rate zones use the applicable bpm boundaries or the supported configured method. Missing or invalid settings do not create plausible-looking boundaries.

## Verified example

With FTP 250 W, a power zone from 56% up to 76% spans 140 W inclusive to 190 W exclusive. A sample at exactly 190 W belongs to the next zone. An indoor-specific FTP 200 W would make the same percentages 112–152 W for a matching indoor activity. Running threshold power is resolved independently.

## Time in zone and coverage

Analysis classifies usable recorded time. A distribution can report percentages of classified time while coverage separately reports how much of the recording was classifiable; these are not the same denominator. Unclassified samples must not be interpreted as recovery-zone time. The activity's timer and gap policy depends on the displayed metric; [TRIMP](/learn/trimp/) and [Weighted Power](/learn/weighted-power/) document their load projections.

## Setting changes

Effective dates and source context determine the threshold used for an activity. A new threshold is not automatically valid before its recorded date. Recalculation can change zone distributions, PI and PSS; merely reviewing [eFTP](/learn/eftp/) does not apply it. Workout target zones use the relevant authoring settings and export conversion rules. [Training Zones and Thresholds](/features/training-zones/) shows where to edit them.

## Sources and implementation scope

[Coggan, power-based training metrics](https://www.trainingpeaks.com/learn/articles/normalized-power-intensity-factor-training-stress/) 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.