Technique for detecting MUAP propagation from high-threshold motor units

A technique was developed to identify the propagation pattern of high-threshold motor unit action potentials (MUAPs) in human skeletal muscles. A linear surface array and a selective needle electrode were used simultaneously for detection of myoelectric signals during a constant-force isometric voluntary contraction. The needle signals were decomposed into trains of single MUAPs and were used to trigger-average the surface signals. After averaging 16 channels of surface signals derived with the linear array electrode, we obtained the propagation of single MUAPs along the muscle fibers. The special quadrifilar needle electrode and the algorithm for decomposing the needle signals made it possible to detect high-threshold MUs recruited at