Dario Farina1, Roberto Merletti2, Roger M Enoka3. 1. Department of Neurorehabilitation Engineering, Bernstein Focus Neurotechnology Göttingen, Bernstein Center for Computational Neuroscience, University Medical Center Göttingen, Georg-August University, Göttingen, Germany; dario.farina@bccn.uni-goettingen.de. 2. Laboratory for Engineering of the Neuromuscular System, Department of Electronics and Telecommunications, Politecnico di Torino, Turin, Italy; and. 3. Department of Integrative Physiology, University of Colorado Boulder, Colorado.