Motor Control after Human SCI Through Activation of Muscle Synergies under Spinal Cord Stimulation

Richard Cheng, Yanan Sui, Dimitry Sayenko, Joel W. Burdick

Research output: Contribution to journalArticlepeer-review

9 Scopus citations


Spinal cord stimulation (SCS) has enabled motor recovery in paraplegics with motor complete spinal cord injury (SCI). However, the physiological mechanisms underlying this recovery are unknown. This paper analyzes muscle synergies in two motor complete SCI patients under SCS during standing and compares them with muscle synergies in healthy subjects, in order to help elucidate the mechanisms that enable motor control through SCS. One challenge is that standard muscle synergy extraction algorithms, such as non-negative matrix factorization (NMF), fail when applied to SCI patients under SCS. We develop a new algorithm-rShiftNMF-to extract muscle synergies in these cases. We find muscle synergies extracted by rShiftNMF are significantly better at interpreting electromyography (EMG) activity, and resulting synergy features are more physiologically meaningful. By analyzing muscle synergies from SCI patients and healthy subjects, we find that: 1) SCI patients rely significantly on muscle synergy activation to generate motor activity; 2) interleaving SCS can selectively activate an additional muscle synergy that is critical to SCI standing; and 3) muscle synergies extracted from SCI patients under SCS differ substantially from those extracted from healthy subjects. We provide evidence that after spinal cord injury, SCS influences motor function through muscle synergy activation.

Original languageEnglish (US)
Article number8704925
Pages (from-to)1331-1340
Number of pages10
JournalIEEE Transactions on Neural Systems and Rehabilitation Engineering
Issue number6
StatePublished - Jun 2019


  • Muscle synergy
  • electromyography (EMG)
  • matrix factorization
  • spinal cord injury (SCI)
  • spinal cord stimulation (SCI)

ASJC Scopus subject areas

  • Internal Medicine
  • Neuroscience(all)
  • Biomedical Engineering


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