Affiliations: [a] Center for Biomedical Engineering and Physics, Medical University of Vienna, Vienna, Austria | [b] Otto Bock Healthcare Products GmbH, Vienna, Austria | [c] Department of Physical Medicine and Rehabilitation, Wilhelminenspital, Vienna, Austria | [x] Institute for Fundamental and Clinical Movement Science, Faculty of Movement Sciences, Vrije Universiteit, Amsterdam, The Netherlands | [y] Rehabilitation Center “Amsterdam”, Amsterdam, The Netherlands | [z] Delft University of Technology, Delft, The Netherlands
Correspondence:
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Address for correspondence: Manfred Bijak Ph.D., Center for Biomedical Engineering and Physics, Medical University of Vienna, Waehringer Guertel 18-20/4L, A-1090 Vienna, Austria. Tel.: +43 1 40400 1992; Fax: +43 1 40400 3988; E-mail: [email protected].
Abstract: Seven paraplegic Functional Electrical Stimulation (FES) experienced users volunteered to test a newly developed eight channel stimulation system. The goal was to discover the influence of various stimulation parameters on the gait quality. As additional task the usability should be improved and simplified as much as possible. Commercially available hydrogel electrodes were attached to quadriceps and gluteus muscles to achieve hip and knee extension, to peroneal nerve to elicit flexion reflex and later also to adductor muscles. All patients were positive about the handling of the stimulation system. Especially the wireless remote control was highly approved. First results demonstrate the importance of an amplitude ramp during stimulation onset (0.1–0.4 s) resulting in a smooth and more “natural” movement. For an adequate step length and walking speed the timing of quadriceps and peroneal nerve stimulation at the end of the swing phase are crucial. Experienced patients with a higher walking speed require a short swing phase and an overlap of quadriceps decay and peronaeus onset (0–0.2 s). Activation of the adductor muscles reduces knee abduction and lead to a better knee trajectory during standing up and better leg movement during the swing phase. Patients can perform 15–25 steps per minute with a step length of 20–30 cm. The walking distance until exhaustion or muscle fatigue occurs is 4–60 m. The analysis of the used stimulation sequences brought up guidelines for a fast and effective parameter optimization procedure.
