150 vs 195 Steps Per Minute — Same Pace, What Changes?

Same runner, same 10 km/h treadmill pace — a 30-minute 5K. The only thing that changes is cadence: 150, 165, 180, 195 steps per minute.

At 150 spm his foot lands 30 cm ahead of his centre of mass. At 195, 12 cm. The part of the step *behind* him barely moves — so almost the entire difference shows up out in front, as braking.

How this is made: Fitlapse videos are 3D simulations, not motion capture. The runner is an anatomical model and the stride is generated from set parameters — cadence, ground-contact time, landing offset — then measured back off the rendered model to confirm it does what was asked. The direction of every effect is checked against published running research. Treat it as a controlled experiment in software, not a recording of a real person.