Muscle activities in similar arms performing identical tasks reveal the neural basis of muscle synergies


Are the muscle synergies extracted from multiple electromyographic signals an expression of neural information processing, or rather a by-product of mechanical and task constraints? To address this question, we asked 41 right-handed adults to perform a variety of motor tasks with their left and right arms. The analysis of the muscle activities resulted in the identification of synergies whose activation was different for the two sides. In particular, tasks involving the control of isometric forces resulted in larger differences. As the two arms essentially have identical biomechanical structure, we concluded that the differences observed in the activation of the respective synergies must be attributed to neural control.

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Data availability

The data sets analyzed during the current study are available from the corresponding author upon reasonable request.


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The authors are grateful to all participants of the study for volunteering their time. We want to thank Giorgia Stranieri, Amel Chief and Maddalena Mugnosso for the help during the experimental sessions, Dr. Susanna Summa and Dr. Camilla Pierella for helpful suggestions, Prof. Ferdinando Mussa-Ivaldi for his advice and critical review of the manuscript, Prof. Niels Birbaumer for his further revision of the manuscript, and Brenda Klem for proofreading the manuscript.


This research was supported by Italian Multiple Sclerosis Foundation (FISM, 2013- Cod. 2013/R/5) and by Marie Curie Integration Grant FP7-PEOPLE- 2012-CIG- 334201 (REMAKE) Research projects of national interest (ModuLimb, PRIN-2015HFWRYY).

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All the authors conceived the study, designed the experimental protocol and developed the experimental setup. LP collected the data. All authors analyzed the results, contributed to the discussion of the results and to writing of the manuscript. All authors read and approved the final manuscript.

Correspondence to Maura Casadio.

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Communicated by Francesco Lacquaniti.

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Pellegrino, L., Coscia, M. & Casadio, M. Muscle activities in similar arms performing identical tasks reveal the neural basis of muscle synergies. Exp Brain Res 238, 121–138 (2020).

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  • Upper limb
  • Robotic evaluation
  • Reaching
  • Electromyography