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Adelaide Research and Scholarship
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Schools and Disciplines
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School of Molecular and Biomedical Science
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Physiology
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Physiology Publications
Permanent link to this item:
http://hdl.handle.net/2440/52144
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| Type: | Article |
| Title: | Motor Unit Synchronization is Increased in Biceps Brachii after Exercise-Induced Damage to Elbow Flexor Muscles |
| Author: | Dartnall, Tamara Jade
Nordstrom, Michael Andrew
Semmler, John Gregory |
| Citation: | Journal of Neurophysiology, 2008; 99(2):1008-1019 |
| Publisher: | Amer Physiological Soc |
| Issue Date: | 2008 |
| ISSN: | 0022-3077 |
| School/Discipline: | School of Molecular and Biomedical Science : Physiology |
Statement of
Responsibility: | Tamara J. Dartnall, Michael A. Nordstrom and John G. Semmler |
| Abstract: | The purpose of this study was to determine the effect of eccentric exercise on correlated motor unit discharge (motor unit synchronization and coherence) during low-force contractions of the human biceps brachii muscle. Eight subjects (age, 25 ± 7 yr) performed three tasks involving isometric contraction of elbow flexors while EMG (surface and intramuscular) records were obtained from biceps brachii. Tasks were 1) maximum voluntary contraction (MVC); 2) constant-force contraction at various submaximal targets; and 3) sustained discharge of pairs of concurrently active motor units for 2–5 min. These tasks were performed before, immediately after, and 24 h after fatiguing eccentric exercise. MVC force declined 46% immediately after eccentric exercise and remained depressed (31%) 24 h later, which is indicative of muscle damage. For the constant-force task, biceps brachii EMG (~100% greater) and force fluctuations (~75% greater) increased immediately after exercise, and both recovered by ~50% 24 h later. Motor unit synchronization, quantified by cross-correlation of motor unit pairs during low-force (1–26% MVC) contractions, was 30% greater immediately after (n = 105 pairs) and 24 h after exercise (n = 92 pairs) compared with before exercise (n = 99 pairs). Similarly, motor unit coherence at low (0–10 Hz) frequencies was 20% greater immediately after exercise and 34% greater 24 h later. These results indicate that the series of events leading to muscle damage from eccentric exercise alters the correlated behavior of human motor units in biceps brachii muscle for ≥24 h after the exercise. |
| RMID: | 0020080014 |
| DOI: | 10.1152/jn.00686.2007 |
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| Appears in Collections: | Physiology Publications
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