Document Detail

Stability of corticospinal excitability and grip force in intrinsic hand muscles in man over a 24-h period.
MedLine Citation:
PMID:  12954409     Owner:  NLM     Status:  MEDLINE    
The maximum voluntary muscle force can vary throughout the day; typically being low in the morning and high in the evening. The nature of this possible variation has been investigated with respect to corticospinal excitability. Six healthy subjects were studied. Maximum voluntary contraction (MVC) in the thenar muscles was measured. In addition, we monitored several indices of corticospinal excitability using electromyographic (EMG) recording and transcranial magnetic stimulation (TMS) of the motor cortex. Motor evoked potentials (MEPs) were recorded while relaxed and at 10% MVC when the silent period was assessed as an index of corticospinal inhibition. Readings were taken every 3 h for 24 h. MVC of the thenar muscles did not change significantly over the 24 h. The mean areas, latencies and durations of MEPs did not show significant changes over the 24-h test period with the muscle relaxed or contracted; however, MEP area did vary between sessions at all stimulus intensities suggesting non-time-of-day-dependent changes in corticospinal excitability. Furthermore, the extent and duration of the silent period seen after the MEP in the contracted muscle did not change significantly over the 24 h of the experiment at any stimulus intensity. These results provide evidence that the MVC force of the thenar muscles and their responses to TMS are stable throughout the course of the day and suggest that, in hand muscles, corticospinal excitability may not be subject to circadian variation.
Paul H Strutton; Maria Catley; Nick J Davey
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Publication Detail:
Type:  Journal Article; Research Support, Non-U.S. Gov't    
Journal Detail:
Title:  Physiology & behavior     Volume:  79     ISSN:  0031-9384     ISO Abbreviation:  Physiol. Behav.     Publication Date:  2003 Sep 
Date Detail:
Created Date:  2003-09-04     Completed Date:  2004-05-19     Revised Date:  2006-11-15    
Medline Journal Info:
Nlm Unique ID:  0151504     Medline TA:  Physiol Behav     Country:  United States    
Other Details:
Languages:  eng     Pagination:  679-82     Citation Subset:  IM    
Division of Neuroscience and Psychological Medicine, Department of Sensorimotor Systems, Faculty of Medicine, Imperial College London, Charing Cross Campus, London W6 8RP, UK.
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MeSH Terms
Arousal / physiology*
Cerebral Cortex / physiology*
Circadian Rhythm / physiology*
Evoked Potentials, Motor / physiology
Hand Strength / physiology*
Middle Aged
Muscle, Skeletal / innervation,  physiology
Neural Pathways / physiology
Spinal Cord / physiology*

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