Sum of phase-shifted sinusoids stimulation prolongs paralyzed muscle output

Neuroprostheses can help people with paralysis stand and move. Current systems cause rapid muscle fatigue because they use constant stimulation. Sum of Phase-shifted Sinusoids (SOPS) stimulation may improve this by activating different muscle groups at different times. SOPS stimulation selectively modulates activation of individual motor unit pools (MUPs) to lower the duty cycle of each while maintaining a high net muscle output. This approach has been shown to improve joint moment maintenance but introduces instability. This study used a real-time feedback controller with SOPS stimulation and found it decreased joint moment instability and prolonged joint moment output. This suggests that closed-loop SOPS has the potential to improve neuroprosthetic systems.

• 1
  Open and closed-loop SOPS stimulation prolonged time to fatigue (TF) and increased total work (W) compared to constant stimulation.
• 2
  Closed-loop SOPS stimulation prolonged time below target (TBT) compared to open-loop SOPS and constant stimulation and decreased moment ripple (R) compared to open-loop SOPS.
• 3
  Both open and closed-loop SOPS maintained a lower stimulation cost (C), the ratio of charge injection to work performed (Q/W), than constant stimulation.