The effects of unilateral muscle fatigue on bilateral physiological tremor

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Title The effects of unilateral muscle fatigue on bilateral physiological tremor
Author Morrison, Steven; Kavanagh, Justin; Obst, Steven John; Irwin, Jemma; Haseler, Luke Jonathon
Journal Name Experimental Brain Research
Editor J.C. Rothwell
Year Published 2005
Place of publication Germany
Publisher Springer-Verlag
Abstract The aim of this study was to examine the post-exercise effects of fatiguing the wrist extensor muscles of a single arm on postural tremor and muscle activity in both arms. Previous research has shown that, for neurologically normal subjects, the tremor seen within a single limb segment is uncorrelated to that seen contralaterally. However it has been speculated that some bilateral relation does exist, and that the nature of the relation may only become evident under conditions where the neuromuscular system is perturbed. To further investigate this potential bilateral relation, seven healthy subjects were required to adopt a bilateral postural pointing position after exercise-induced fatigue of the wrist extensor muscles of a single arm. Tremor from the forearm, hand and finger segments of each arm, surface EMG activity from extensor digitorum (ED) of each arm, and blood lactate data were collected prior to and after the exercise intervention. The main result was that fatiguing the distal muscles of one arm resulted in a bilateral increase in both the physiological tremor and ED activity. The change in tremor was confined to the index finger with no change in the tremor for the hand or forearm segments of either arm. While three peaks were seen in the frequency profile of the finger tremor, the effects of fatigue were confined to an increase in the peak power of the neurally generated 8–12 Hz tremor component. The contralateral increase in muscle activity was also reflected by a change in the frequency profile of the EMG output, with an increase in the peak power of both muscles following exercise of the wrist extensors of a single arm. The bilateral increases in physiological tremor and EMG activity of ED were only observed during the bilateral pointing task, with no changes in tremor or EMG activity seen for the non-exercised limb during the unilateral exercise protocol. The specificity of the resultant increases in the neurally generated 8–12 Hz component of finger tremor amplitude and EMG activity, coupled with the lack of any changes in tremor for the more proximal arm segments, indicate that these bilateral effects were mediated by an increase in the central neural drive to both limbs. Together this set of results challenges the general assumption of bilateral independence of tremor production, and further illustrate the task dependent nature of exercise-induced fatigue.
Peer Reviewed Yes
Published Yes
Alternative URI http://dx.doi.org/10.1007/s00221-005-0050-x
Volume 167
Page from 609
Page to 621
ISSN 0014-4819
Date Accessioned 2006-03-17
Language en_AU
Research Centre Centre for Musculoskeletal Research; Griffith Health Institute; Heart Foundation Research Centre
Faculty Griffith Health Faculty
Subject PRE2009-Motor Control
URI http://hdl.handle.net/10072/4708
Publication Type Journal Articles (Refereed Article)
Publication Type Code c1

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