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Localised task‐dependent motor‐unit recruitment in the masseter
Author(s) -
Schindler H. J.,
Hellmann D.,
Giannakopoulos N. N.,
Eiglsperger U.,
Dijk J. P.,
Lapatki B. G.
Publication year - 2014
Publication title -
journal of oral rehabilitation
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.991
H-Index - 93
eISSN - 1365-2842
pISSN - 0305-182X
DOI - 10.1111/joor.12168
Subject(s) - masticatory force , masseter muscle , bite force quotient , motor unit , task (project management) , electromyography , mastication , physical medicine and rehabilitation , anatomy , orthodontics , medicine , management , economics
Summary Localised motor‐unit ( MU ) recruitment in the masseter was analysed in this study. We investigated whether differential activation behaviour, which has already been reported for distant masseter regions, can also be detected in small muscle subvolumes at the level of single MU s. Two bipolar fine‐wire electrodes and an intra‐oral 3D bite‐force transmitter were used to record intra‐muscular electromyograms ( EMG ) resulting from controlled bite‐forces of 10 healthy human subjects (mean age 24·1 ± 1·2 years). Two‐hundred and seventeen decomposed MU s were organised into localised MU task groups with different ( P < 0·001) force‐direction‐specific behaviour. Proportions of MU s involved in one, two, three or four examined tasks were 46%, 31%, 18% and 5%, respectively. This study provides evidence of the ability of the neuromuscular system to modify the mechanical output of small masseter subvolumes by differential control of adjacent MU s belonging to distinct task groups. Localised differential activation behaviour of the masseter may be the crucial factor enabling highly flexible and efficient adjustment of the muscle activity in response to complex local biomechanical needs, for example, continually varying bite‐forces during the demanding masticatory process.