Klinische Neurophysiologie 2006; 37 - A216
DOI: 10.1055/s-2006-939299

Functional output performance in paraplegic cycling propelled by leg stimulation with middle frequency alternating current

J Szecsi 1, P Krause 1, S Krafczyk 1, T Brandt 1, A Straube 1
  • 1Zentrum für Sensomotorik der Neurologischen Klinik der LMU, München

Introduction: A requirement of functional electrical stimulation (FES), which is used extensively in rehabilitation of paraplegics, is that the stimulation should elicit a sufficiently powerful muscle contraction with minimum discomfort and fatigue. Although low frequency rectangular pulsed current (LFRP) is usually used, information has been increasing, that middle frequency alternating current (MFAC) reduces the fatigue rate more than LFRP. Additionally could be expected that MFAC causes less pain, thus allowing stimulation of sensory incomplete paraplegics. Because such MFAC stimulation-induced lower fatigue rate is a trade-off with force reduction, it is important to determine whether MFAC stimulation is a realistic option for FES of paraplegics.

Fig. 1

Fig. 2

Objective: To compare the isometric force, power, and pain sensations during FES cycling of paraplegics during electrical stimulation using MFAC or standard LFRP.

Methods: Eleven complete paraplegic subjects participated. Isometric torques of the leg muscles and the pedaling power generated in the first 20 minutes during ergometer cycling were collected during stimulation (Fig. 1) with 20Hz LFRP or 4 KHz sinusoidal modulated with 50Hz MFAC (a total of four sessions). Subjectively sensed pain was quantitatively recorded during ergometer cycling at maximal stimulation with the visual analogue scale (VAS) method.

Results: Isometric torque elicited during MFAC stimulation was significantly lower (p<0.02). Moreover, mean pedaling power generated during MFAC was highly and significantly lower (p<0.001) than during standard LFRP stimulation (Fig. 2). While there were no complains registered during LFRP stimulation, four of eleven participants reported an abdominal, tugging discomfort during MFAC stimulation (mean VAS=3.2).

Conclusion: From a clinical viewpoint MFAC is not a viable option for enhancing functional output or for minimizing discomfort during FES of complete and incomplete paraplegics.