Document Detail


Maximal voluntary fingertip force production is not limited by movement speed in combined motion and force tasks.
MedLine Citation:
PMID:  19587285     Owner:  NLM     Status:  MEDLINE    
Abstract/OtherAbstract:
Numerous studies of limbs and fingers propose that force-velocity properties of muscle limit maximal voluntary force production during anisometric tasks, i.e., when muscles are shortening or lengthening. Although this proposition appears logical, our study on the simultaneous production of fingertip motion and force disagrees with this commonly held notion. We asked eight consenting adults to use their dominant index fingertip to maximize voluntary downward force against a horizontal surface at specific postures (static trials), and also during an anisometric "scratching" task of rhythmically moving the fingertip along a 5.8 +/- 0.5 cm target line. The metronome-timed flexion-extension movement speed varied 36-fold from "slow" (1.0 +/- 0.5 cm/s) to "fast" (35.9 +/- 7.8 cm/s). As expected, maximal downward voluntary force diminished (44.8 +/- 15.6%; p = 0.001) when any motion (slow or fast) was added to the task. Surprisingly, however, a 36-fold increase in speed did not affect this reduction in force magnitude. These remarkable results for such an ordinary task challenge the dominant role often attributed to force-velocity properties of muscle and provide insight into neuromechanical interactions. We propose an explanation that the simultaneous enforcement of mechanical constraints for motion and force reduces the set of feasible motor commands sufficiently so that force-velocity properties cease to be the force-limiting factor. While additional work is necessary to reveal the governing mechanisms, the dramatic influence that the simultaneous enforcement of motion and force constraints has on force output begins to explain the vulnerability of dexterous function to development, aging, and even mild neuromuscular pathology.
Authors:
Kevin G Keenan; Veronica J Santos; Madhusudhan Venkadesan; Francisco J Valero-Cuevas
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Publication Detail:
Type:  Comparative Study; Journal Article; Research Support, N.I.H., Extramural; Research Support, U.S. Gov't, Non-P.H.S.    
Journal Detail:
Title:  The Journal of neuroscience : the official journal of the Society for Neuroscience     Volume:  29     ISSN:  1529-2401     ISO Abbreviation:  J. Neurosci.     Publication Date:  2009 Jul 
Date Detail:
Created Date:  2009-07-09     Completed Date:  2009-08-03     Revised Date:  2014-01-14    
Medline Journal Info:
Nlm Unique ID:  8102140     Medline TA:  J Neurosci     Country:  United States    
Other Details:
Languages:  eng     Pagination:  8784-9     Citation Subset:  IM    
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MeSH Terms
Descriptor/Qualifier:
Adult
Biomechanical Phenomena / physiology
Female
Fingers / physiology*
Humans
Male
Movement / physiology*
Muscle, Skeletal / physiology*
Psychomotor Performance / physiology*
Time Factors
Weight-Bearing / physiology
Young Adult
Grant Support
ID/Acronym/Agency:
AR05020/AR/NIAMS NIH HHS; AR052345/AR/NIAMS NIH HHS; HD048566/HD/NICHD NIH HHS; R01 AR050520/AR/NIAMS NIH HHS; R01 AR050520-05/AR/NIAMS NIH HHS; R01 AR052345/AR/NIAMS NIH HHS; R01 AR052345-05/AR/NIAMS NIH HHS
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