[Article] Insights gained into the interpretation of surface electromyograms from the gastrocnemius muscles: A simulation study

[Article] Insights gained into the interpretation of surface electromyograms from the gastrocnemius muscles: A simulation study Porto, the institutional repository of the Politecnico di Torino, is provided by the University Library and the IT-Services. The aim is to enable open access to all the world. Please share with us how this access benefits you. Your story matters. Title: Insights gained into the interpretation of surface electromyograms from the gastrocnemius 1 muscles: a simulation study. ABSTRACT 1 Interpretation of surface electromyograms (EMG) is usually based on the assumption that the 2 surface representation of action potentials does not change during their propagation. This 3 assumption does not hold for muscles whose fibers are oblique to the skin. Consequently, the 4 interpretation of surface EMGs recorded from pinnate muscles unlikely prompts from current 5 knowledge. Here we present a complete analytical model that supports the interpretation of 6 experimental EMGs detected from muscles with oblique architecture. EMGs were recorded from 7 the medial gastrocnemius muscle during voluntary and electrically elicited contractions. 8 Preliminary indications obtained from simulated and experimental signals concern the spatial 9 localization of surface potentials and the myoelectric fatigue. Specifically, the spatial distribution of 10 surface EMGs was localized about the fibers superficial extremity. Strikingly, this localization 11 increased with the pinnation angle, both for the simulated EMGs and the recorded M-waves. 12 Moreover, the average rectified value (ARV) and the mean frequency (MNF) of interference EMGs 13 increased and decreased with fatigue, respectively. Furthermore, the degree of variation in ARV and 14 MNF did not depend on the pinnation angle simulated. Similar variations were observed for the 15 experimental EMGs, although being less evident for a higher fiber inclination. These results are 16 discussed on a physiological context, highlighting the relevance of the model proposed here for the 17 interpretation of gastrocnemius EMGs and for conceiving future experiments on muscles with 18 pinnate geometry.