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Research Papers

Gait Initiation With Electromyographically Triggered Electrical Stimulation in People With Partial Paralysis

[+] Author and Article Information
Anirban Dutta

Cleveland FES Center, Case Western Reserve University, Cleveland, OH 44106adutta@case.edu

Rudi Kobetic, Ronald J. Triolo

Cleveland FES Center, Case Western Reserve University, Cleveland, OH 44106

J Biomech Eng 131(8), 081002 (Jun 19, 2009) (9 pages) doi:10.1115/1.3086356 History: Received October 11, 2007; Revised November 23, 2008; Published June 19, 2009

Functional electrical stimulation (FES) facilitates ambulatory function after paralysis by activating the muscles of the lower extremities. Individuals with incomplete spinal cord injury (iSCI) retain partial volitional control of muscles below the level of injury, necessitating careful integration of FES with intact voluntary motor function for efficient walking. The FES-assisted stepping can be triggered automatically at a fixed rate (autotrigger), by a manual switch (switch-trigger), or by an electromyogram-based gait-event-detector (EMG-trigger). It has been postulated that EMG may be a more natural command source than manual switches, and therefore will enable better coordination of stimulated and volitional motor functions necessary during gait. In this study, the above stated hypothesis was investigated in two volunteers with iSCI during the over-ground FES-assisted gait initiation. Four able-bodied volunteers provided the normative data for comparison. The EMG-triggered FES-assisted gait initiation was found to be more coordinated and dynamically more stable than autotriggered and switch-triggered cases. This highlighted the potential of surface EMG as a natural command interface to better coordinate stimulated and volitional muscle activities during gait.

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Copyright © 2009 by American Society of Mechanical Engineers
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Figures

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Figure 1

Left panel: (a) laboratory setup for EMG-triggered FES-assisted walking; right panel: (b) EMG-based gait-event detector for triggering FES-assisted steps

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Figure 2

Top panel: (a) selection of optimum cut-off frequencies for low-pass filtering the kinematic data; bottom panel: (b) most of power content in the signals was below the optimum cut-off frequency, which were 6 Hz for able-bodied and 3.5 Hz for iSCI data

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Figure 3

Gait initiation protocol during data collection

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Figure 4

Typical pelvis motion in the direction of progression during gait initiation

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Figure 5

Euclidean distance from the origin of the perturbation of the 36 states during gait initiation at the maximum left knee flexion. Left panel: (a) able-bodied data (four subjects); middle panel: (b) subject iSCI-1 data (C1 gait); and right panel: (c) subject iSCI-2 data (C2 gait). (Normative data from four able-bodied subjects, ten trials each; EMG-trigger, switch-trigger, and autotrigger from two iSCI subjects, ten trials each)

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Figure 6

%VAF by the PCs. Top panel: (a) able-bodied data. Bottom panel: (b) two iSCI subjects with EMG, switch, and autotriggered FES. Plots show the data averaged over six gait events.

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Figure 7

Typical loading of the first three PCs on the joint angles (HA: hip angle, KA: knee angle, AA: ankle angle) found from the weight matrix W of the subject Able1. The prefix “l” indicates the left side and “r” indicates the right side. The suffix “x” denotes the sagittal plane, “y” denotes frontal plane, and “z” denotes transverse plane for the joint angles.

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Figure 8

Euclidean distance from the origin of the perturbation of the five principal components at maximum left knee flexion. Left panel: (a) able-bodied (four subjects). Middle panel: (b) subject iSCI-1 (C1 gait). Right panel: (c) subject iSCI-2 (C2 gait). (Normative data from four able-bodied subjects, ten trials each; EMG-trigger, switch-trigger and autotrigger from two iSCI subjects, ten trials each)

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Figure 9

Top panel: (a) scatter plot of QoF and Av. Eig. at six gait events for four able-bodied subjects—Able1, Able2, Able3, and Able4—and the two iSCI subjects with different trigger modes: EMG1, EMG2, SW1, SW2, Auto1, and Auto2. Bottom panel: (b) MANOVA cluster dendrogram plot of the groups.

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Figure 10

Mahalanobis distances matrix between each pair of group means

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