Click on image to view larger version.

Fig. 6. Translational positions and velocities following perturbations relative to
reference positions and velocities. Filled circles are values (mean ± 1
S.D.) for all perturbation trials. Velocities are `errors': the difference
between perturbed velocities and mean reference velocities collected from
unperturbed trials at equivalent phases of the step cycle. Foreaft and
lateral velocities are in the body orientation coordinate frame. Vertical
positions and velocities are in the global coordinate frame. Data from
perturbed trials are normalized so that perturbations occur 30 ms from the
beginning of the data set (indicated by gray vertical lines). N=11
perturbed trials and N=12 unperturbed reference trials.