Fig. 1

Setup in EMG task (a), Prosthesis task without feedback (b), and Prosthesis task with feedback (c). The desired level of normalized muscle activation (EMG task) or prosthesis force (Prosthesis tasks) was shown on the computer screen (full line, L5). All other levels were indicated with dashed lines. The lowest level was not used as target level (see text for further explanation). In the Prosthesis task without feedback, the subjects could see and hear the prosthesis but did not see the level of generated force. In the Prosthesis task with feedback, they additionally received visual feedback on the generated force (bar in c)