Stimulation of paralysed quadriceps muscles with sequentially and spatially distributed electrodes during dynamic knee e
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(2019) 16:5
RESEARCH
Open Access
Stimulation of paralysed quadriceps muscles with sequentially and spatially distributed electrodes during dynamic knee extension Marco Laubacher1,2* , Efe A. Aksoez1,2 , Anne K. Brust3 , Michael Baumberger3 , Robert Riener2 , Stuart Binder-Macleod4 and Kenneth J. Hunt1 Abstract Background: During functional electrical stimulation (FES) tasks with able-bodied (AB) participants, spatially distributed sequential stimulation (SDSS) has demonstrated substantial improvements in power output and fatigue properties compared to conventional single electrode stimulation (SES). The aim of this study was to compare the properties of SDSS and SES in participants with spinal cord injury (SCI) in a dynamic isokinetic knee extension task simulating knee movement during recumbent cycling. Method: Using a case-series design, m. vastus lateralis and medialis of four participants with motor and sensory complete SCI (AIS A) were stimulated for 6 min on both legs with both electrode setups. With SES, target muscles were stimulated by a pair of electrodes. In SDSS, the distal electrodes were replaced by four small electrodes giving the same overall stimulation frequency and having the same total surface area. Torque was measured during knee extension by a dynamometer at an angular velocity of 110 deg/s. Mean power of the left and right sides (PmeanL,R ) was calculated from all stimulated extensions for initial, final and all extensions. Fatigue is presented as an index value with respect to initial power from 1 to 0, whereby 1 means no fatigue. Results: SDSS showed higher PmeanL,R values for all four participants for all extensions (increases of 132% in participant P1, 100% in P2, 36% in P3 and 18% in P4 compared to SES) and for the initial phase (increases of 84%, 59%, 66%, and 16%, respectively). Fatigue resistance was better with SDSS for P1, P2 and P4 but worse for P3 (0.47 vs 0.35, 0.63 vs 0.49, 0.90 vs 0.82 and 0.59 vs 0.77, respectively). Conclusion: Consistently higher PmeanL,R was observed for all four participants for initial and overall contractions using SDSS. This supports findings from previous studies with AB participants. Fatigue properties were better in three of the four participants. The lower fatigue resistance with SDSS in one participant may be explained by a very low muscle activation level in this case. Further investigation in a larger cohort is warranted. Keywords: Functional electrical stimulation, Spinal cord injury, Rehabilitation, Spatially distributed sequential stimulation, Knee dynamometer, Power output, Fatigue
*Correspondence: [email protected] Institute for Rehabilitation and Performance Technology, Division of Mechanical Engineering, Department of Engineering and Information Technology, Bern University of Applied Sciences, Pestalozzistrasse 20, 3400 Burgdorf, Switzerland 2 Sensory Motor Systems Lab, Department of Health Sciences and Technology, ETH Zurich, 8000 Zurich, Switzerland Full list of author information is available at the end of the article 1
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