Comment on "Can muscle coordination be precisely studied by surface electromyography?".

Despite the many reviews and research papers on the limitations of surface electromyography (EMG), there are relatively few that address this issue by considering dynamic contractions and specifically from the point of view of muscle coordination. Nevertheless, whether muscle coordination can be precisely studied using surface EMG signals is still a matter of discussion in the scientific community. In other words, it is uncertain whether neural control strategies of movement can be inferred from EMG. This review article discusses the appropriateness of using EMG recordings for studying muscle coordination. First, the main uses of surface EMG for studying muscle coordination are depicted. Then, the main intrinsic drawbacks of the EMG technique (i.e., amplitude cancellation, crosstalk and spatial variability of muscle activity) and of EMG processing (i.e., smoothing of the linear envelope, normalization of the time scale and the amplitude and timing of muscle activation) are described and discussed. Finally, three other factors (i.e., variability, electromechanical delay and neuromuscular fatigue), which can affect the interpretation of EMG and have received little attention in the literature, are presented and discussed. All of this information is crucial to the proper interpretation of muscle coordination from EMG signals.