RT Journal Article SR Electronic T1 Larger and Denser: An Optimal Design for Surface Grids of EMG Electrodes to Identify Greater and More Representative Samples of Motor Units JF eneuro JO eNeuro FD Society for Neuroscience SP ENEURO.0064-23.2023 DO 10.1523/ENEURO.0064-23.2023 VO 10 IS 9 A1 Arnault H. Caillet A1 Simon Avrillon A1 Aritra Kundu A1 Tianyi Yu A1 Andrew T. M. Phillips A1 Luca Modenese A1 Dario Farina YR 2023 UL http://www.eneuro.org/content/10/9/ENEURO.0064-23.2023.abstract AB The spinal motor neurons are the only neural cells whose individual activity can be noninvasively identified. This is usually done using grids of surface electromyographic (EMG) electrodes and source separation algorithms; an approach called EMG decomposition. In this study, we combined computational and experimental analyses to assess how the design parameters of grids of electrodes influence the number and the properties of the identified motor units. We first computed the percentage of motor units that could be theoretically discriminated within a pool of 200 simulated motor units when decomposing EMG signals recorded with grids of various sizes and interelectrode distances (IEDs). Increasing the density, the number of electrodes, and the size of the grids, increased the number of motor units that our decomposition algorithm could theoretically discriminate, i.e., up to 83.5% of the simulated pool (range across conditions: 30.5–83.5%). We then identified motor units from experimental EMG signals recorded in six participants with grids of various sizes (range: 2–36 cm2) and IED (range: 4–16 mm). The configuration with the largest number of electrodes and the shortest IED maximized the number of identified motor units (56 ± 14; range: 39–79) and the percentage of early recruited motor units within these samples (29 ± 14%). Finally, the number of identified motor units further increased with a prototyped grid of 256 electrodes and an IED of 2 mm. Taken together, our results showed that larger and denser surface grids of electrodes allow to identify a more representative pool of motor units than currently reported in experimental studies.