Document Detail

Age-associated changes in motor unit physiology: observations from the Baltimore Longitudinal Study of Aging.
MedLine Citation:
PMID:  19577038     Owner:  NLM     Status:  MEDLINE    
OBJECTIVE: To examine motor unit characteristics (size and firing rate) associated with aging. DESIGN: Cross-sectional, observational. SETTING: Community. PARTICIPANTS: Baltimore Longitudinal Study of Aging participants (N=102), aged 22.2 to 94.1 years, were studied. INTERVENTIONS: Not applicable. MAIN OUTCOME MEASURES: Surface-represented motor unit size and firing rate were collected from the vastus medialis during knee extension at 10%, 20%, 30%, and 50% of each subject's maximum isometric voluntary contraction (MVC). RESULTS: MVC declined with older age (P<.0001). Adjusting for differences in MVC, both firing rate and motor unit size per newton force generated began to increase in the 6th decade of life. Motor unit size increased per newton force to a greater extent than firing rate. Those over the age of 75 years also activated significantly larger motor units per unit force (P=.04). Relative to force generated, the average firing rate began increasing at 57.8+/-3.4 years and between 50.2 and 56.4 years (+/-4y) for motor unit size. CONCLUSIONS: The size of motor units and firing rates used to achieve a given force changes with age, particularly after middle age. Whether these changes precede, follow, or occur concurrent to age-related modifications in muscle structure and contractile properties or sarcopenia is not known.
Shari M Ling; Robin A Conwit; Luigi Ferrucci; E Jeffrey Metter
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Publication Detail:
Type:  Journal Article; Research Support, N.I.H., Intramural    
Journal Detail:
Title:  Archives of physical medicine and rehabilitation     Volume:  90     ISSN:  1532-821X     ISO Abbreviation:  Arch Phys Med Rehabil     Publication Date:  2009 Jul 
Date Detail:
Created Date:  2009-07-06     Completed Date:  2009-07-21     Revised Date:  -    
Medline Journal Info:
Nlm Unique ID:  2985158R     Medline TA:  Arch Phys Med Rehabil     Country:  United States    
Other Details:
Languages:  eng     Pagination:  1237-40     Citation Subset:  AIM; IM    
Clinical Research Branch, National Institute on Aging Intramural Research Program, National Institutes of Health, Baltimore, MD, USA.
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MeSH Terms
Action Potentials
Aged, 80 and over
Aging / physiology*
Cross-Sectional Studies
Isometric Contraction
Longitudinal Studies
Middle Aged
Motor Neurons / physiology*
Muscle, Skeletal / innervation*,  physiology

From MEDLINE®/PubMed®, a database of the U.S. National Library of Medicine

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