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).


METHODS
Repeated-measures.


METHODS
Laboratory setting.


METHODS
Eleven otherwise healthy volunteer subjects with SCI (8 with American Spinal Injury Association [ASIA] grade A, 3 with ASIA grade B).


METHODS
To evaluate cycling-relevant differences between LFRP and modulated MFAC stimulation, we exposed participants to isometric measurements and cycling experiments performed during both 20 Hz LFRP and 4 KHz modulated with 50 Hz MFAC.


METHODS
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.
Szecsi
Johann
J
Center for Sensorimotor Research, Department of Neurology, Ludwig-Maximillians University, Munich, Germany. jszecsi@nefo.uni-muenchen.de
Fornusek
Ché
C
Krause
Phillip
P
Straube
Andreas
A
D000293:Adolescent; D000328:Adult; D001642:Bicycling / Q000502:physiology*; D004599:Electric Stimulation Therapy / Q000379:methods*; D016552:Ergometry; D005260:Female; D006801:Humans; D007537:Isometric Contraction / Q000502:physiology; D008297:Male; D008875:Middle Aged; D018763:Muscle Fatigue / Q000502:physiology; D018482:Muscle, Skeletal / Q000503:physiopathology*; D010147:Pain Measurement; D013119:Spinal Cord Injuries / Q000503:physiopathology / Q000534:rehabilitation*; D019415:Torque