Figure 2.

A (Fixed) and B (AAN1) show the ankle trajectories recorded over 30 s of movement for the fixed-trajectory and the AAN1 paradigms, respectively. The colored areas represent the average EMG activity recorded from the soleus and TA muscles: red, soleus activity; green, TA activity; yellow, soleus and TA muscle coactivation. The intensity of the color is directly proportional to the amplitude of the EMG signal. The arrows point to examples of changes in direction attributable to the robotic arm guiding the ankle toward the trajectory. C shows the raw EMG activity of the soleus and TA muscles during 3.0 s of movement for each paradigm (top, Fixed; bottom, AAN1). D shows the averaged integrated EMG for the soleus (red) and TA (green) muscles from over 30 continuous seconds of stepping for each paradigm (left, Fixed; right, AAN1). The **** section represents the stance phase of the step cycle.