Influência dos parâmetros estimulatórios na eficiência da contração muscular evocada pela estimulação elétrica funcional em pessoas hígidas ou com lesão medular

Abstract

Introduction: Functional electrical stimulation (FES) is applied to people with spinal cord injury (SCI) in order to artificially evoque functional movements. Mechanomyography (MMG) measures the oscillation of the muscle during contraction. The stimulatory profiles are controlled by the parameters: active and rest periods of the pulse and the burst and their amplitude. During the period of application of FES, the neuromuscular tissue responds in different ways, due to physiological changes such as muscle fatigue and/or adaptation of motor neurons. Objective: In the research developed, we investigated the influence of simulatory parameters on the efficiency of muscle contraction evoked by FES in healthy volunteers and patients with spinal cord injury. Materials and Methods: The healthy volunteers (HV) and ten subjects with SCI participated of the study. The MMG sensors were placed over the belly of the rectus femoris muscle and vastus lateralis. The electrical stimuli were yielded on the femoral nerve in order to activate quadriceps muscle. Five FES profiles were tested on different days with eight artificially evoked contractions divided into two sessions with an interval of fifteen minutes apart. Results: was proposed a FES efficiency index based on (1) stimulation time, (2) lower angular variation and (3) lower divergence of MMG descriptors: Median Frequency (MF) and Root Mean Square (RMS) value. FES profiles that showed better efficiency are: burst frequency of 50 Hz for HV and 70 Hz for SCI volunteers. They kept the contraction artificially evoked for (1) longer time, (2) lower angular variation of and (3) mechanomyographic response with minor modification. Conclusions: we conclude thar stimulatory profiles using frequencies of 50 Hz for HV and 70 Hz for SCI volunteers were more efficient for evoking contraction artificially.