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Fig. 3 | Journal of NeuroEngineering and Rehabilitation

Fig. 3

From: Proportional estimation of finger movements from high-density surface electromyography

Fig. 3

Three phases of the online experiment. a sEMG Root Mean Square (RMS) maps calculated over a 200-ms data window of (1 RMS sample). The RMS for each channel (white circle) was color coded as indicated by the color legend (μV), and the pixels between the channels were obtained by interpolation. The figure shows one representative subject performing isometric sustained contractions of individual fingers in the direction of flexion or extension. The fingers produce characteristic and spatially localized, but partly overlapping, EMG responses. b Training data collection. The subjects were asked to reproduce trapezoidal reference activation profiles (i.e., gradual increase, plateau, gradual decrease) with plateau at 30, 60 and 90 % of MVC of the respective finger. The red and blue lines depict the generated and reference activation levels from an example tracking trial at 60 %, respectively. c Online test where the subjects controlled 4 visual markers (blue circles), each associated with the activation of one finger, as indicated by the horizontal axis. The vertical position of the marker was set by the output of the tested control method (LDA, CSP-PE and THR) computing the estimated finger activation level. The subjects therefore proportionally controlled the vertical position of the marker by increasing or decreasing the finger force in the direction of flexion (marker moving downward) or extension (marker moving upward). The task for the subject was to activate the fingers, one at a time, tracking online the reference marker (red sphere) moving along vertical direction and representing the desired finger activation level

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