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Fig. 5 | Journal of NeuroEngineering and Rehabilitation

Fig. 5

From: Epidural stimulation restores muscle synergies by modulating neural drives in participants with sensorimotor complete spinal cord injuries

Fig. 5

Number of muscle synergies determined from coefficient of determination (\(R^2\)) curves across different therapeutic conditions. The number of synergies is determined from a threshold of 85\(\%\) of the \(R^2\) value. The \(R^2\) value (y axis) is plotted against the number of factors/synergies (x-axis) for SCI participants under different conditions (no stimulation and stimulation in the 1st session, 5th session, and last session) and control participants. The left, middle, and right panels in the top row display left, BL, and right hip movements. The left, middle, and right panels in the bottom row display left, BL, and right ankle movements. In the absence of stimulation, all ten components were required to explain at least 85\(\%\) variability in the data. During eSCS, a dose-dependent reduction in dimensionality was observed. In the last session, the number of synergies for the SCI participants was very close to that for the control participants. We found that a total of four muscle synergies were needed to explain 85% of the variance in the data-the same number of synergies needed for the control participants. Moreover, two SCI participants (SCI001, SCI002) were able to maintain the reduced dimensionality and improved motor function in the absence of stimulation. The \(R^2\) curve for them is shown in Additional file 1: Figure S2

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