Centimeter Differences in Wrist Electrode Placement Significantly Impact Myoelectric Performance

The long-term goal of this research is to establish electromyography (EMG) as an intuitive and dexterous control interface for human-computer interaction. EMG is an established technique for classifying hand gestures and motions, used often in prosthetics and orthotics. Recently, there has been a shift towards recording EMG at the wrist, instead of at the forearm, to yield a more socially acceptable form factor for consumer applications. EMG within the size of a watch or bracelet means fewer electrodes and more variable placement with respect to the underlying muscle anatomy. Here, we explore how differences in location along the wrist impact EMG quality and myoelectric control. We recorded EMG and compared myoelectric performance across three different regions of electrodes (distal, central, and proximal) using electrode arrays at both the wrist and the forearm. We found that a small 4.3 cm shift proximally on the wrist yields significant improvements in EMG information content and myoelectric performance. When trained on a k-Nearest Neighbors model, classification accuracy increased from 79.3% at the distal wrist region to 83.7% at the proximal wrist position. EMG from the proximal wrist region also had significantly more information content, as indicated by greater variance outside of the first principal component and by more frequently selected channels via a minimum-redundancy-maximum-relevance selection approach. These findings indicate that the spatial position of electrodes at the wrist has a noticeable impact on myoelectric control in a way not seen in traditional EMG recordings from the forearm. This can inform the design of future wrist-worn EMG devices, which in turn may lead to more robust control for partial hand prostheses, hand orthoses, and augmented/virtual reality.Clinical Relevance- A subtle change in the position of electromyographic electrodes on the wrist can yield significant improvements in the control of technology, like prostheses, exoskeletons, and virtual/augmented reality.