J Electromyogr Kinesiol. 2010 Aug 12.

Alternating stimulation of synergistic muscles during functional electrical stimulation cycling improves endurance in persons with spinal cord injury.

Decker MJ, Griffin L, Abraham LD, Brandt L.

Department of Kinesiology and Health Education, University of Texas at Austin, United States.

Therapeutic effects of functional electrical stimulation (FES) cycling for persons with spinal cord injury (SCI) are limited by high rates of muscular fatigue. FES-cycling performance limits and surface mechanomyography (MMG) of 12 persons with SCI were compared under two different stimulation protocols of the quadriceps muscles. One strategy used the standard "co-activation" protocol from the manufacturer of the FES cycle which involved intermittent simultaneous activation of the entire quadriceps muscle group for 400ms. The other strategy was an "alternation" stimulation protocol which involved alternately stimulating the rectus femoris (RF) muscle for 100ms and the vastus medialis (VM) and vastus lateralis (VL) muscles for 100ms, with two sets with a 400ms burst. Thus, during the alternation protocol, each of the muscle groups rested for two 100ms "off" periods in each 400ms burst. There was no difference in average cycling cadence (28RPM) between the two protocols. The alternation stimulation protocol produced longer ride times and longer virtual distances traveled and used lower stimulation intensity levels with no differences in average MMG amplitudes compared to the co-activation protocol. These results demonstrate that FES-cycling performance can be enhanced by a synergistic muscle alternation stimulation strategy.