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Eccentric exercise increases EMG amplitude and force fluctuations during submaximal contractions of elbow flexor muscles

¹Discipline of Physiology and Research Centre for Human Movement Control, School of Molecular and Biomedical Science, University of Adelaide, Adelaide; and ²Department of Physiology, Monash University, Melbourne, Australia

Submitted 19 November 2006 ; accepted in final form 25 June 2007

The purpose of this study was to determine the effect of eccentric exercise on the ability to exert steady submaximal forces with muscles that cross the elbow joint. Eight subjects performed two tasks requiring isometric contraction of the right elbow flexors: a maximum voluntary contraction (MVC) and a constant-force task at four submaximal target forces (5, 20, 35, 50% MVC) while electromyography (EMG) was recorded from elbow flexor and extensor muscles. These tasks were performed before, after, and 24 h after a period of eccentric (fatigue and muscle damage) or concentric exercise (fatigue only). MVC force declined after eccentric exercise (45% decline) and remained depressed 24 h later (24%), whereas the reduced force after concentric exercise (22%) fully recovered the following day. EMG amplitude during the submaximal contractions increased in all elbow flexor muscles after eccentric exercise, with the greatest change in the biceps brachii at low forces (3–4 times larger at 5 and 20% MVC) and in the brachialis muscle at moderate forces (2 times larger at 35 and 50% MVC). Eccentric exercise resulted in a twofold increase in coactivation of the triceps brachii muscle during all submaximal contractions. Force fluctuations were larger after eccentric exercise, particularly at low forces (3–4 times larger at 5% MVC, 2 times larger at 50% MVC), with a twofold increase in physiological tremor at 8–12 Hz. These data indicate that eccentric exercise results in impaired motor control and altered neural drive to elbow flexor muscles, particularly at low forces, suggesting altered motor unit activation after eccentric exercise.

electromyography; motor control; muscle damage

This article has been cited by other articles:

				J. M. Dundon, J. Cirillo, and J. G. Semmler Low-frequency fatigue and neuromuscular performance after exercise-induced damage to elbow flexor muscles J Appl Physiol, October 1, 2008; 105(4): 1146 - 1155. [Abstract] [Full Text] [PDF]

				T. S. Turner, K. J. Tucker, N. C. Rogasch, and J. G. Semmler Impaired neuromuscular function during isometric, shortening, and lengthening contractions after exercise-induced damage to elbow flexor muscles J Appl Physiol, August 1, 2008; 105(2): 502 - 509. [Abstract] [Full Text] [PDF]

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