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In an experimental study on the changes in descending drive during muscle fatigue, Semmler et al.(2013) investigated intermuscular (EMG–EMG) coherence in elbow muscles after eccentric exercise. They reported a broadband increase in coherence with fatigue in all elbow flexor muscle pairs and suggested that these changes reflect increased common oscillatory input to the elbow flexors. This interpretation was questioned in the Editorial by Heroux and Gandevia (2013), who noted that the mechanisms generating the reported increase in coherence are unclear and that peripheral factors such as EMG signal cancellation may provide an alternative explanation for the observed changes in coherence. Héroux and Gandevia therefore, concluded that the insights that can be obtained from investigating corticomuscular (CMC) and intermuscular (IMC) coherence are limited.

In this commentary, I will first revisited the reasons for investigating IMC and CMC. These measures have the potential to provide key insights into the composition of descending drive (Farmer, 1998) and involve non-invasive recording techniques that make them suitable for clinical applications. Subsequently, I will review current research in this area aimed to uncover the generating mechanisms of IMC and CMC. In particular, the use of computational modeling and new recording techniques are considered to obtain a more accurate estimate of the underlying changes in descending drive. CMC and IMC can provide important insights into the diverging projects underlying motor coordination. A major open questions in motor control is how the