Figure 2.

A. Representative example of one perturbation trial of a single subject displaying knee displacement, target template, and error following perturbations. B, C and D show ensemble average of 10 perturbations superimposed over trials in which no perturbation was delivered. In B, the dotted line represents the template, the dark line represents knee displacement during no perturbation and dashed line shows knee displacement when perturbed. In C and D, muscular responses of the vastus medialis and lateral hamstrings are shown. The dotted trace shows the trials in which no perturbation was given and the dark trace is the average of trials in which perturbations were delivered. Note the enhanced quadriceps response and inhibition of the hamstrings in response to the perturbation