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- Title
Functional properties of single motor units in the human medial pterygoid muscle: Thresholds.
- Authors
Chen, Hui; Whittle, Terry; Gal, John; Klineberg, Iven J.; Murray, Greg M.
- Abstract
Background: Little is known regarding the functional properties of single motor units (SMUs) in the medial pterygoid muscle (MPt) during jaw movements. Objectives: The aims are (a) to report the thresholds of onset of MPt SMUs during 4 goal‐directed jaw movement tasks, and (b) to determine whether the threshold of onset of SMU activation varies with the velocity of jaw movement and the location within the muscle. Methods: Intra‐muscular electrodes were inserted in the right MPt of 18 participants performing ipsilateral (right), contralateral, protrusive and opening‐closing jaw movements recorded at 2 velocities. Task phases were as follows: BEFORE, OUT, HOLDING, RETURN and AFTER. SMU onset thresholds were determined from the displacement (mm) of the lower mid‐incisor point. Electrode location within 4 arbitrary muscle divisions was determined with computer tomography. Statistical tests: Spearman's correlations, Kruskal‐Wallis tests; significance accepted at P <.05. Results: A significant inverse relation occurred between velocity and threshold for the RETURN of the ipsilateral movement (n = 62 SMU thresholds), while a significant positive relation occurred for the OUT of the contralateral movement (n = 208); there were no significant associations for the protrusive (n = 131) and opening‐closing (n = 58) tasks. Significant threshold differences occurred across the 4 muscle divisions only during the OUT of the contralateral and protrusive movements. Some evidence was provided for gender differences in MPt SMU properties. Conclusions: The absence of a significant inverse relation between velocity and SMU threshold for most recorded movements suggests the MPt acts as a stabilizer of the jaw in horizontal and opening‐closing jaw movements.
- Subjects
PTERYGOID muscles; MOTOR unit; MOTOR ability; JAW abnormalities; THRESHOLDING algorithms; COMPUTED tomography; VELOCITY measurements; MOVEMENT ratio
- Publication
Journal of Oral Rehabilitation, 2021, Vol 48, Issue 2, p132
- ISSN
0305-182X
- Publication type
Article
- DOI
10.1111/joor.13115