Cadence

Why this matters

Cadence — steps per minute, counting both feet — is the single most-actionable number in distance running. It is the frequency half of the speed equation (speed = cadence × step length), and unlike step length it can be changed consciously, immediately, with no extra fitness. Nudging cadence up at the same pace forces each foot to land closer under the body's centre of mass, which shortens the lever the ground pushes back through. The downstream effects are large and well-documented: less over-stride, a lower braking impulse at contact, reduced peak knee and hip load, and a smaller vertical oscillation (you bounce less when steps are quicker).

It is also the cheapest fatigue marker you can track. As a runner tires, step length collapses faster than cadence, so a runner who holds cadence late in a piece is defending their mechanics; one whose cadence sags is shortening and softening every step. Comparing the first and last counting windows of a run tells you more than any single reading.

The often-quoted "180" is a population average, not a target — optimal cadence scales with height, leg length and speed. The 165–185 band here is the efficient window for most adult runners at endurance pace; tall runners sit lower, shorter runners higher, and everyone rises with speed.

How it's measured here — and the slow-motion trap

This is a windowed count, not a per-step detector. Scrub to a clean step to open the window, scrub to a clean step to close it, then count the foot contacts in between. Rate = contacts ÷ window-seconds × 60. Counting whole steps and aligning both ends on the same point of the gait cycle keeps the window unbiased.

The one thing that will wreck the reading is slow-motion footage. Phone slow-mo is captured at a high frame rate (120 or 240 fps) but its timestamps are written as if it plays at 30 fps — so a 1-second real window stretches to 4 or 8 video-seconds, and an uncorrected cadence reads 4–8× too low (a real 184 spm shows as ~23). Set the clip's Capture FPS in the Clip Inspector (e.g. 240) so the tool rescales video-time back to real time before computing the rate. A correct reading lands back in the 160–200 range.

What good looks like

165–185 steps/min at easy-to-moderate pace, holding steady (±2–3 spm) across the run. Each foot lands roughly under the hip, the stride looks "quick and quiet", and the runner is not visibly reaching the lead foot out ahead.

Common faults

• Low cadence (< 165 spm) — the classic over-strider's signature. The lead foot reaches ahead, lands heel-first as a brake, and the quadriceps eat a hard eccentric load. Almost always pairs with a longer Step Length and a far-forward stride angle.
• Cadence sag across the run — a first-window of 180 falling to 165 by the end is mechanical fatigue: the runner is conserving energy by shortening the swing. Worth more attention than the absolute number.
• High cadence at easy pace (> 185 spm) — usually fine and efficient, but if it appears at a slow pace it can mean step length has collapsed; cross-check that the stride isn't stuttering.

Coaching cues

• "Quick feet — count to 90 on one foot per minute." Lifting cadence ~5 % at the same pace is the most reliable way to pull a foot back under the body.
• A metronome or a 180-bpm playlist trains the frequency without the runner thinking about it.
• Don't chase a number blindly — raise cadence and re-check step length and stride angle to confirm the mechanics actually improved.

Related measurements

• Step Length — the other half of speed; low cadence and a long step span describe the same over-stride from two angles.
• Stride Angle — the geometry of where the foot lands; over-stride shows here as a far-forward tibia.
• Initial Contact — Knee Flexion — a stiff, locked knee at contact typically accompanies a low cadence.