Nonlinear Methods on HD-sEMG Signals for Aging Effect Evaluation During Isometric Contractions of the Biceps Brachii

Muscle aging is associated with a loss of muscle mass and strength. Different factors are responsible, which can possibly lead to a modification of the complexity of the neuromuscular system. This may be reflected in electromyogram signals. In this study, we have tried to analyze the nonlinearity and chaotic characteristics of high-density surface electromyography (HD-sEMG) from Biceps Brachii (BB) during isometric contractions, at low and moderate levels, recorded from young and elderly people. For this purpose, three measures widely employed in nonlinearity detection were used: Time reversibility (Tr), Sample Entropy (SE), and Delay Vector Variance (DVV). For comparison purposes, the Root Mean Square amplitude (RMSA) was also computed. The results indicated that SE and Tr are significantly higher in elderly people. Furthermore, signal complexity decreases with contraction level for all categories.