Evaluation of HD- sEMG grid misalignment with muscle fibers using nonlinear correlation

Abstract

International audienceIn a recent past, several techniques have been developed to analyze the effect of electrode grid alignment with the muscle fibers. But, they focused on pattern matching of Motor Unit (MU) electrical signatures and not on the interference signal. In this study, we use a method which is widely applied in connectivity and directionality analysis of stochastic and complex signals, namely, the nonlinear correlation coefficient (h²) on HD-sEMG signal matrices. The approach is first applied on simulated data from recent generation model through an (8x8) simulated electrode matrix, then on real signals using the same grid specifications on the Biceps Brachii. Both simulated and real data were evaluated with three angles of grid alignment with respect to muscle fibers. For this purpose, five parameters were extracted from obtained h² correlation matrices and tested. According to the obtained results, a relationship between h² values and the electrode matrix alignment seems to exist. However, further efforts are needed to design parameters more sensitive to grid misalignment with respect to muscle fibers

Sensitivity analysis of HD-sEMG amplitude descriptors relative to grid parameter variations of a cylindrical multilayered muscle model

“…A misalignment of a few degree will bias the recording signals between the subjects and thus, give false interpretation of the results. This result is in agreement with a previous study [22] where authors only studied the rotation effect of the grid according to the fiber orientation. Also, the lateral center of the grid has to be carefully chosen.…”