Theory 19/Froude Number/Human gait
The Walk-Run Transition Is Froude
The claim
The walk-to-run transition occurs at a critical Froude number rather than at a critical speed, so leg length sets the speed at which people switch.
01Mechanism
Gait choice trades inverted-pendulum mechanics against spring-mass mechanics; the ratio of inertial to gravitational forces determines which is cheaper.
02Prediction
Transition speed should scale with the square root of leg length.
03Refutation
Transition at a fixed speed across body sizes would remove the ratio.