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Load across sports: cycling, running, swimming and strength on one scale

Your body does not distinguish between cycling and running when it comes to fatigue. For fitness, fatigue and form to be right, every session needs a load number on the same scale.

Updated: October 6, 2026 · 5 min read

One scale for everything

The reference is always the same rule: one hour exactly at your threshold equals 100 points. In cycling the threshold is FTP, in running threshold pace, in swimming critical swim speed (CSS). That way a ride and a run can be added up, and fitness, fatigue and form apply across all sports.

How precise it is per sport

Cycling with a power meter: most precise (TSS).
Running with pace: good (rTSS), somewhat too low on hills without elevation data. Running power in watts does not currently feed into load.
Swimming with distance and time: usable (sTSS), from 200 m continuous. Because water resistance rises steeply with speed, load increases more with intensity than in running.
Heart rate only: estimate via your threshold heart rate, only if you have turned on heart rate load (not for swimming). Good for steady sessions, less precise for intervals.
Strength and core: There is no established formula for it. Without heart rate a session gets no load number; with heart rate and heart rate load turned on, ZonePit treats it like a heart-rate session.

Every session shows what its load is based on, so you know how far to trust the number.

What it means for planning

No two hard days in a row, not even across sports. A hard run after hard bike intervals is just as tiring.
Your main sport gets the key sessions. Other sports complement at an easy level.
Running needs more caution when building up than cycling or swimming, because impact stresses tendons and bones more. Volume therefore grows more slowly.
Leg-heavy strength training does not belong right before a key session.

In ZonePit

ZonePit converts the load of every session from Apple Health to this common scale and plans your week by these rules. In History you see weekly load by sport.

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Keep reading

Sources

Andrew Coggan: Training Stress Score (TSS), TrainingPeaks.
Stephen McGregor (2008): Running Training Stress Score (rTSS), TrainingPeaks.
TrainingPeaks: Calculating Swimming TSS Score (sTSS, CSS).

ZonePit is a training and wellness app, not a medical device.