# Activity Metrics: Work, Efficiency and Intensity Minutes

Canonical HTML: https://effortsignal.com/learn/activity-metrics/

Last content update: 2026-09-10

These summaries answer different questions and retain their own units and source requirements.

## Mechanical work

On the projected one-second timer-running power sequence, mechanical work in kilojoules is sum(valid power in watts) / 1000. Real zero watts count; missing power is not invented. For 3,600 seconds at 200 W, work is 720 kJ. This is mechanical work, not a direct calorie measurement. The applicable power-coverage gate and timer rules are described in [Weighted Power](/learn/weighted-power/).

## Efficiency factor

Cycling efficiency factor divides Weighted Power by average HR, in W/bpm. At 200 W and 150 bpm, it is 1.333333 W/bpm. Running uses average speed in m/s divided by average HR. Neither ratio is metabolic efficiency. Missing output or a nonpositive/unavailable mean HR prevents a meaningful ratio. [Aerobic Decoupling](/learn/aerobic-decoupling/) compares this relationship between halves with additional sport and terrain gates.

## Relative heart rate

Average HR as percent maximum is 100 × mean HR / maximum HR. Percent threshold uses lactate-threshold HR instead. Heart-rate reserve percent is 100 × (mean HR − resting HR) / (maximum HR − resting HR). At mean 150, resting 50 and maximum 190 bpm, percent maximum is 78.947368% and reserve percent is 71.428571%. These activity ratios require at least 90% HR coverage and valid applicable profile values. They are not interchangeable with each other or with [TRIMP](/learn/trimp/).

## Intensity minutes

For each valid timer-running HR second, reserve ratio at least 0.50 and below 0.70 earns moderate time; at least 0.70 earns vigorous time. Total intensity-minute credit = moderate minutes + 2 × vigorous minutes. The calculation needs at least 90% HR coverage, resting HR and maximum HR greater than resting HR. At a constant 150 bpm with resting 50 and maximum 190, one hour earns 60 vigorous minutes and 120 credited intensity minutes. Credit can exceed clock duration and does not add 120 minutes to the activity or alter ATL/CTL.

## Source and settings

The [training-load monitoring consensus](https://pubmed.ncbi.nlm.nih.gov/28463642/) provides general context for separating measurements and derived metrics; it does not specify these product rules. These formulas and examples describe EffortSignal 0.1.13, checked September 10, 2026. Changed applicable thresholds, corrected samples and recalculation can change the derived values. [Activity Analysis](/features/activity-analysis/) keeps them with their recording.