“Fine synergies” describe motor adaptation in people with drop foot in a way that supplements traditional “coarse synergies”

Frontiers in Sports and Active Living

Sports and Active Living

Hesam Azadjou¹  Francisco J. Valero-Cuevas²  Angelo Bartsch-Jimenez³  Michalina Błażkiewicz⁴  Ryan Novotny⁵ 

[1] Biomedical Engineering Department, University of Southern California, Los Angeles, CA, United States;Division of Biokinesiology and Physical Therapy, University of Southern California, Los Angeles, CA, United States;Biomedical Engineering Department, University of Southern California, Los Angeles, CA, United States;Division of Biokinesiology and Physical Therapy, University of Southern California, Los Angeles, CA, United States;Escuela de Kinesiología, Facultad de Medicina, Universidad de Valparaíso, Valparaíso, Chile;Józef Piłsudski University of Physical Education in Warsaw, Warsaw, Poland;Neuroscience Graduate Program, University of Southern California, Los Angeles, CA, United States;

关键词: electromyography;    muscle synergies;    non-negative matrix factorization;    drop foot;    gait;   

DOI  :  10.3389/fspor.2023.1080170

 received in 2022-10-25, accepted in 2023-01-13,  发布年份 2023

来源: Frontiers

【 摘 要 】

Synergy analysis via dimensionality reduction is a standard approach in biomechanics to capture the dominant features of limb kinematics or muscle activation signals, which can be called “coarse synergies.” Here we demonstrate that the less dominant features of these signals, which are often explicitly disregarded or considered noise, can nevertheless exhibit “fine synergies” that reveal subtle, yet functionally important, adaptations. To find the coarse synergies, we applied non-negative matrix factorization (NMF) to unilateral EMG data from eight muscles of the involved leg in ten people with drop-foot (DF), and of the right leg of 16 unimpaired (control) participants. We then extracted the fine synergies for each group by removing the coarse synergies (i.e., first two factors explaining ≥85% of variance) from the data and applying Principal Component Analysis (PCA) to those residuals. Surprisingly, the time histories and structure of the coarse EMG synergies showed few differences between DF and controls—even though the kinematics of drop-foot gait is evidently different from unimpaired gait. In contrast, the structure of the fine EMG synergies (as per their PCA loadings) showed significant differences between groups. In particular, loadings for Tibialis Anterior, Peroneus Longus, Gastrocnemius Lateralis, Biceps and Rectus Femoris, Vastus Medialis and Lateralis muscles differed between groups (p<0.05). We conclude that the multiple differences found in the structure of the fine synergies extracted from EMG in people with drop-foot vs. unimpaired controls—not visible in the coarse synergies—likely reflect differences in their motor strategies. Coarse synergies, in contrast, seem to mostly reflect the gross features of EMG in bipedal gait that must be met by all participants—and thus show few differences between groups. However, drawing insights into the clinical origin of these differences requires well-controlled clinical trials. We propose that fine synergies should not be disregarded in biomechanical analysis, as they may be more informative of the disruption and adaptation of muscle coordination strategies in participants due to drop-foot, age and/or other gait impairments.

【 授权许可】

Unknown   
© 2023 Bartsch-Jiménez, Valero-Cuevas, Blazkiewicz, Azadjou and Novotny.