4:13 vs 2:06 Marathon — What Actually Changes?
Two runners, same body, same height — one on four-hour marathon pace, one on two-hour.
The surprise: the steps per minute barely move (168 → 186). Almost all of the speed comes from how far each step travels — 0.99 m becomes 1.79 m. Nearly double the ground, same legs.
What you're seeing, beat by beat: • How long each foot stays on the road • How much of each stride happens in the air • How tightly the knee folds through the swing • How far one step actually covers
Muscle glow shows which muscles are working, rendered in 3D from the Fitlapse anatomy engine.
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