The Optimal Electrical Stimulation Frequency to Improve the Muscle Endurance in Spinal Cord Injured Rabbit

ABSTRACT

OBJECTIVE: Clinical application of Functional Electrical Stimulation (FES) was limited due to the muscle fatigue phenomenon. This study was undertaken to find an electrical stimulation frequency, which optimally improves muscle endurance in spinal cord injured rabbit. METHOD: Fifteen rabbits were experimentally spinal cord injured at the T10 or T11 spinal cord level. Three kinds of stimulation frequency (10, 20, 40 Hz) and sham control stimulation were applied to the tibialis anterior muscle of each four group for 1 hour per day, for 2 weeks. Muscle fatigue index and peak torque were measured during electrical stimulation, and proportion of the type I musclefiber was measured at ATPase (pH 9.4) staining. RESULTS: Complete paraplegia was obtained in all 12 rabbits. Muscle fatigue index and peak torque were not changed after 2 weeks of electrical stimulation in all four groups. The proportion of the type I muscle fiber was reduced in all four groups after 2 weeks. However, 40 Hz stimulation group showed less decline in proportion of type I muscle fiber than control or 10 Hz group. CONCLUSION: High frequency electrical stimulation applied at an early stage of spinal cord injury is more effective in preserving muscle endurance than low frequency stimulation.