Low-Frequency Rectangular Pulse Is Superior to Middle Frequency Alternating Current Stimulation in Cycling of People With Spinal Cord Injury
Abstract
Szecsi J, Fornusek C, Krause P, Straube A. Low-frequency rectangular pulse is superior to middle frequency alternating current stimulation in cycling of people with spinal cord injury.
Objective
To determine the efficacy of using modulated middle frequency alternating current (MFAC) muscle stimulation for functional electric stimulation–propelled cycling by people with spinal cord injury (SCI) compared with the conventional method of using standard low-frequency rectangular pulses (LFRP).
Design
Repeated-measures.
Setting
Laboratory setting.
Participants
Eleven otherwise healthy volunteer subjects with SCI (8 with American Spinal Injury Association [ASIA] grade A, 3 with ASIA grade B).
Interventions
To evaluate cycling-relevant differences between LFRP and modulated MFAC stimulation, we exposed participants to isometric measurements and cycling experiments performed during both 20Hz LFRP and 4KHz modulated with 50Hz MFAC.
Main Outcome Measures
We recorded maximal isometric torque, maximal dynamic work during 20 minutes of ergometer cycling, and perceived discomfort for each of the 2 stimulation patterns.
Results
Both the isometric torque (P<.02) and work generated (P<.001) during MFAC stimulation were significantly lower than during standard LFRP stimulation. Four participants reported discomfort and 1 of them also developed skin burns during MFAC stimulation.
Conclusions
Our findings suggest that in SCI subjects, stimulated cycling with low frequency is generally more effective than cycling with modulated MFAC in terms of torque, work, and pain sensation.
aCenter for Sensorimotor Research, Dept. of Neurology, Ludwig-Maximillians University, Munich, Germany
bRehabilitation Research Centre, School of Exercise and Sports Science, Faculty of Health Sciences, University of Sydney, Sydney, Australia.
Reprint requests to Johann Szecsi, MD, MSc (Eng), Center for Sensorimotor Research, Dept of Neurology, Ludwig-Maximillians University, Marchioninistr 23, 81377 Munich, Germany
Supported by the Else-Kröner Fresenius Foundation, Bad Homburg, Germany.
No commercial party having a direct financial interest in the results of the research supporting this article has or will confer a benefit upon the author(s) or upon any organization with which the author(s) is/are associated.
ABSTRACT