Ken Roberts

what's here

  • intro

  • Phases of stroke-cycle | two-leg coordination

  • Timing coordination for smaller moves

see also


?? [ more to be added ]


Phases of stroke-cycle

[ set-down instant ]

0 = (optional) overlap of feet on ground for Walking)

1 = pull-back (foot is on ground with ankle-joint in front of hip-joint of pushing leg)

2 = push-back (foot is on ground with ankle-joint in back of hip-joint of pushing leg)

[ lift-off instant ]

J = (optional) both feet off the ground simultaneously.

R = recovery of leg forward


two-leg coordination of the stroke-cycle


Left     Right

1          R

2          R

J           R

R         1

R         2

R         J

1          R


Left     Right

0          3

1          R

2          R

3          0

R         1

R         2

0          3

Timing coordination for smaller moves

Leg Recovery move for running

this timing is mostly driven by the requirements of the main leg push. Key optional point is hold back on the start of recovering the Leg forward during phase J. After lift-up, keep the leg extended with the foot out behind. After the next foot sets down, start the Leg recovering forward.

Arm-swing forward-backward for running

(left Arm coordinating with left Leg)

phase 1 of Leg: arm-backward-swing move decelerates and stops, and immediately arm-forward-swing move starts and accelerates.

phase 2 of Leg: arm-forward-swing continues

phase J of Leg: arm-forward-swing decelerates and stops, and immediately arm-backward-swing starts and accelerates.

phase R of Leg: arm-backward-swing continues

For Torso forward-backward moves

Two coordination options for doing a Torso forward-backward move:

  • once every step, or

  • once every complete stride-cycle.

more . . .

  • The “jump” has a cost in power.

That’s why race-walking can still be pretty fast.

That’s why race runners keep their cadence high and their leaps no longer than necessary.

  • Lots of distance runners keep a quieter torso and arms than the theory above might suggest.