May Angular Variation Be a Parameter for Muscular Condition Classification in SCI People Elicited by Neuromuscular Electrical Stimulation?

People with complete spinal cord injury (SCI) present a rapid process of muscle fatigue under neuromuscular electrical stimulation (NMES) due to neuromuscular impairment. Different NMES patterns interfere with the fatigue process and joint amplitude. The aim of this study was to evaluate muscle reactions using joint knee joint fatigue protocol with four NMES patterns in people with complete SCI. Ten subjects with complete SCI were submitted to 4 stimulatory profiles, with varying pulse duration and the modulating frequency (burst): P1 (100 μs–50 Hz); P2 (100 μs–70 Hz); P3 (200 μs–50 Hz); P4 (200 μs–70 Hz). Subjects were classified according to theirselves angular responses as upper median (UP_med) and lower median (LOW_med). UP_med had lower angular variation and attenuation in the fatigue process than LOW_med in P1 (session I, trial 1 p = 0.06, trial 2 p = 0.009, trial 3 p = 0.029, session II, trial 1 p = 0.015), P2 (session I, trial 3 p = 0.024, trial 4 p = 0.034), P3 (session I, trial 3 p = 0.035), P4 without intergroup difference. The angular variation can be applied as a useful tool for muscular condition classification of complete SCI people. The best performance of UP_med has occurred in P1 and the worst in P4. The LOW_med performance did not stand out in any protocol.