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Territory and fiber orientation of vastus medialis motor units: A Surface electromyography investigation
Author(s) -
Gallina Alessio,
Vieira Taian
Publication year - 2015
Publication title -
muscle and nerve
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.025
H-Index - 145
eISSN - 1097-4598
pISSN - 0148-639X
DOI - 10.1002/mus.24662
Subject(s) - motor unit , electromyography , motor unit recruitment , vastus medialis , orientation (vector space) , anatomy , fiber , patella , materials science , muscle fibre , biomedical engineering , physical medicine and rehabilitation , medicine , mathematics , geometry , composite material , skeletal muscle
The aim of this study was to determine whether muscle fibers innervated by single motor neurons are confined in small subvolumes of the vastus medialis (VM) and if motor unit fiber orientation depends on their position within the muscle. Methods : Single motor units were identified from a grid of surface electrodes. The size of their surface representation and fiber orientation were extracted using an algorithm validated on simulated signals. Results : The action potentials of 77 motor units were represented locally on the skin (10th–90th percentiles: 14–25 mm). According to simulations, this indicates territories smaller than 11.8–64.8 mm. Motor units in distal regions of VM had fibers at a greater angle than those in proximal regions ( R = –0.54, P < 0.001). Conclusion : Motor units with small territories and varying fiber orientations may be an anatomical predisposition to regulate how regions within VM apply forces to the patella. This could help to redistribute loads within the joint in painful conditions. Muscle Nerve 52 : 1057–1065, 2015