Running power: Stryd vs Garmin vs Apple — why the watts do not match
Cycling power is measured; running power is estimated — and each brand estimates it differently, which is why the same run reads different watts on each.
No device measures running power directly
A cycling power meter puts strain gauges in the drivetrain and measures force. Nothing on a runner does that. Stryd infers power from a foot pod’s motion, Garmin from wrist or chest data, Apple from the Watch — each a model turning pace, cadence and motion into an estimate. So three watt figures for one run are three model outputs, and the watt symbol they share hides that they were never measuring the same thing the same way.
What the disagreement is not
The gap between them is not one device being accurate and the others wrong — there is no ground-truth running-power meter to be right against. It is three reasonable estimates of a quantity that has no single agreed definition. Treating one brand’s number as the “real” watts and correcting the others toward it invents a precision none of them has.
What is safe to compare
Each device’s running power is meaningful against itself over time: your Stryd intervals versus your Stryd easy runs, your Garmin build versus your Garmin base. Trends within one model are honest. Cross-brand comparisons, and any training target set in watts, have to stay on the device the target was built for.