Dimensionality of forearm muscle activation in transradial amputees

Abstract

Background Establishing a natural communication interface between the user and the terminal device is one of the central challenges of hand neuroprosthetics research. Surface electromyography (EMG) is the most common source of neural signals for interpreting a user’s intent in these interfaces. However, how the capacity of EMG generation is affected by various clinical parameters remains largely unknown. Methods In this retrospective study using an open source database, we examined the EMG activity of forearm muscles recorded from 11 transradially amputated subjects and 40 able-bodied subjects who performed a wide range of movements. By using non-negative matrix factorization, we extracted the synergistic EMG patterns for each subject to estimate the dimensionality of muscle control, under the framework of motor synergies. Results We found that amputees exhibited less than four synergies (with substantial variability related to the length of remaining limb and age), whereas able-bodied subjects commonly demonstrate five or more synergies. Conclusions The results of this study provide novel insight into the muscle synergy framework and the design of natural myoelectric control interfaces.