Examples of directional tuning of muscle activations.

The mean muscle activation of three muscles recorded from subject 7 are shown as a function of target number (see Fig 2A and 2B) in baseline (blue) and perturbed blocks with perturbation magnitude level 1 (dark red), level 2 (medium red) and level 3 (light red). Note that the targets, defined in Fig 2A, are arranged at the vertices of a dodecahedron. Muscle activation is expressed as the fraction of the MVC recorded during the MVF block (B1).