Sample Entropy-Based Surface Electromyographic Examination with a Linear Electrode Array in Survivors with Spinal Cord Injury.

This study aimed to evaluate the utility of sample entropy (SampEn) of surface electromyographic signals (sEMG) in quantifying neuromuscular changes after spinal cord injury (SCI). Using a linear electrode array, sEMG signals were obtained from the biceps brachii muscles of 13 healthy control subjects and 13 SCI subjects during isometric elbow flexion muscle contraction at various constant force levels. The SampEn analysis was performed on both the representative channel (emerging the largest signal amplitude) and the channel over muscle innervation zone (IZ) determined by the linear array. The SampEn values were further averaged across muscle force levels to examine difference between SCI survivors and control subjects. Results showed that SampEn values after SCI had a significantly greater range than those of the control subjects at the group level. Abnormal increases or decreases in SampEn were also found after SCI at the individual subject level. In addition, a significant difference was found between the representative channel and the IZ channel. SampEn is a valuable indicator for identifying neuromuscular changes after SCI, and the effect of the IZ on the sEMG examination is particularly noteworthy. The approach presented in this study may facilitate the development of appropriate rehabilitation methods to enhance motor recovery.