THE EFFECT OF FATIGUE OCCURRENCE IN QUADRICEPS MUSCLE OF SPINAL CORD INJURY PATIENTS WHO USE FUNCTIONAL NEURAL ELECTRICAL STIMULATION REHABILITATION DEVICES: AN OBSERVATIONAL STUDY

In this study, the critical limit of muscle fatigue was evaluated for patients who use Functional Neural Electrical Stimulation (FNES) rehabilitation devices for walking. These patients do not have voluntary muscle control and have to be artificially stimulated to walk and their fatigue is not recognized in time because of the lack of sensation in their muscles. With the help of this system, it is done more safely and its usage can speed up the training process.

In this study, the time of approaching the critical point of fatigue for Quadriceps muscles in patients with spinal cord injury was investigated. Patients having the injury level between T4-T12 were randomly selected. A system was designed to stimulate the Quadriceps muscle and identify the results before reaching critical fatigue.

By adjusting the electrical stimulation diagrams and the modified electromyogram diagram in the early cycles of quadriceps muscle stimulation, the muscle initially started with a higher slope, but after 5–8 cycles, this difference reached its minimum. This slope difference begins again when approaching the fatigue phase. The voltage required to stimulate the female patients was 180 volts and the male patients needed 225 volts to raise their shins by 60 degrees.

The results of the experiments after the MVIC of quadriceps reached 80% averaged over 290 cycles equivalent to 232 m. There was also a significant relationship between regular use of the device and delay in the onset of muscle fatigue (p <0.001). After repeated testing, all subjects experienced fatigue after a longer period (11% on average).