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Year : 2017  |  Volume : 1  |  Issue : 2  |  Page : 21-27

Influence of joint angle and biceps brachii isometric contraction intensity on electromyographic and mechanomyographic responses

Department of Exercise Science, Bloomsburg University of Pennsylvania, Bloomsburg, PA, United States of America

Correspondence Address:
Swapan Mookerjee
Bloomsburg University, Department of Exercise Science, 400 East 2nd St., Bloomsburg, PA, 17815
United States of America
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Source of Support: None, Conflict of Interest: None

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Purpose: This study was designed to: a) examine the influence of elbow joint angle and contraction intensity on electromyographic (EMG) and mechanomyographic (MMG) responses using linear slope coefficients and, b) further describe these relationships utilizing polynomial regression. Methods: 14 male subjects (mean ± SD, age 22.1 ± 2.3 years) performed maximal voluntary isometric contractions (MVC) at elbow flexion angles of 60°, 90°, and 120°. Subjects then performed 35 second contractions at two MVC levels (50%, 75%) for each joint angle. EMG and MMG were recorded simultaneously from the biceps brachii. The center 30 second segment of the signal was utilized to determine the root-mean-square (RMS). Results: No significant effect of elbow joint angle was found for the EMG (p = 0.52) and MMG (p = 0.12) slope coefficient analysis, as well as contraction intensity (EMG: p = 0.61; MMG: p = 0.50). Composite polynomial regression revealed that the MMG-Time relationships were best fit with linear models at 120° (50% MVC: p = 0.025; 75% MVC: p = 0.019), while non-linear relationships best described the 60° (50% MVC, 75% MVC: p < 0.001) and 90° (50% MVC, 75% MVC: p < 0.001) joint angles. Conclusions: Results indicate that motor control strategies are not significantly different between elbow joint angles when utilizing linear regression models. However, polynomial regression revealed elbow joint angle specific MMG-Time relationships. Non-linear, MMG-Time relationships are influenced by elbow joint angle during short-term, sustained isometric contractions.

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