Muscle activation patterns and muscle synergies reflect different modes of coordination during upper extremity movement

Front Hum Neurosci. 2023 Jan 18:16:912440. doi: 10.3389/fnhum.2022.912440. eCollection 2022.

Abstract

A core issue in motor control is how the central nervous system generates and selects the muscle activation patterns necessary to achieve a variety of behaviors and movements. Extensive studies have verified that it is the foundation to induce a complex movement by the modular combinations of several muscles with a synergetic relationship. However, a few studies focus on the synergetic similarity and dissimilarity among different types of movements, especially for the upper extremity movements. In this study, we introduced the non-negative matrix factorization (NMF) method to explore the muscle activation patterns and synergy structure under 6 types of movements, involving the hand open (HO), hand close (HC), wrist flexion (WF), wrist extension (WE), supination (SU), and pronation (PR). For this, we enrolled 10 healthy subjects to record the electromyography signal for NMF calculation. The results showed a highly modular similarity of the muscle synergy among subjects under the same movement. Furthermore, Spearman's correlation analysis indicated significant similarities among HO-WE, HO-SU, and WE-SU (p < 0.001). Additionally, we also found shared synergy and special synergy in activation patterns among different movements. This study confirmed the theory of modular structure in the central nervous system, which yields a stable synergetic pattern under the same movement. Our findings on muscle synergy will be of great significance to motor control and even to clinical assessment techniques.

Keywords: motor control; muscle activation patterns; muscle synergies; non-negative matrix factorization; surface electromyography.

Grants and funding

This research was supported jointly by the National Natural Science Foundation of China (Grant Nos. 61901407, U20A20192, and 62076216), the S&T Program of Hebei (Grant Nos. 21372005D and 21372001D), Cultivation Project for Basic Research and Innovation of Yanshan University (Grant No. 2021LGZD010), and the Funding Program for Innovative Ability Training of Graduate Students of Hebei Provincial Department of Education (Grant No. CXZZSS2022123).