Duty factor

The share of each stride spent with the foot on the ground, expressed as a ratio between 0 and 1.

Why it matters

Duty factor is a compact way to judge whether your stride is grounded and shuffling or springy and elastic, without tracking separate GCT and flight-time numbers.

What it means

Duty factor (GCT ÷ stride time) typically falls between 0.35 and 0.45 in distance runners. Lower values indicate a springier, more elastic stride; higher values indicate a grounded, shuffling stride. Duty factor rises predictably as pace slows, so it's most useful compared at a matched pace or against your own baseline over time.