The placement of the electrodes and the visual feedback interface. (a) and (b) are an example of the electrode positions at the ventral and dorsal side of the forearm, respectively. The electrode numbers are marked in the photo. (c)-(f) are the visual feedback interface for the online performance tests. (c) the range of movement of the feedback arrow, with the arrow in neutral position (white arrow). Example of arrow in non-neutral position (dashed grey arrow). (d) Example of target during a target reaching attempt (right handed supination movement). (e) Grasping test initial setting, with the arrow in neutral position and object to grasp (dark blue line). (f) Grasping test force feedback once the object is reached. The white circle is the force feedback (diameter proportional to the force level, as estimated from the EMG), the yellow circles represent the upper and lower limit of the target force level. When the white circle moves outside large yellow circle which corresponds to the lower force limit, an ‘open’ function is activated.