Document Detail

Motor unit firing rates and contractile properties in tibialis anterior of young and old men.
MedLine Citation:
PMID:  10444648     Owner:  NLM     Status:  MEDLINE    
The effects of aging on motoneuron firing rates and muscle contractile properties were studied in tibialis anterior muscle by comparing results from six young (20.8 +/- 0.8 yr) and six old men (82.0 +/- 1.7 yr). For each subject, data were collected from repeated tests over a 2-wk period. Contractile tests included maximal voluntary contraction (MVC) with twitch interpolation and stimulated twitch contractions. The old men had 26% lower MVC torque (P < 0.01) than did the young men, but percent activation was not different (99.1 and 99.3%, respectively). Twitch contraction durations were 23% longer (P < 0.01) in the old compared with the young men. During a series of repeated brief steady-state contractions at 10, 25, 50, 75, and 100% MVC, motor unit firing rates were recorded. Results from approximately 950 motor unit trains in each subject group indicated that at all relative torque levels mean firing rates were 30-35% lower (P < 0.01) in the old subjects. Comparisons between young and old subjects' mean firing rates at each of 10%, 50%, and MVC torques and their corresponding mean twitch contraction duration yielded a range of moderate-to-high correlations (r = -0.67 to -0.84). That lower firing rates were matched to longer twitch contraction durations in the muscle of old men, and relatively higher firing rates were matched with shorter contraction times from the young men, indirectly supports the neuromuscular age-related remodeling principle.
D M Connelly; C L Rice; M R Roos; A A Vandervoort
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Publication Detail:
Type:  Comparative Study; Journal Article; Research Support, Non-U.S. Gov't    
Journal Detail:
Title:  Journal of applied physiology (Bethesda, Md. : 1985)     Volume:  87     ISSN:  8750-7587     ISO Abbreviation:  J. Appl. Physiol.     Publication Date:  1999 Aug 
Date Detail:
Created Date:  1999-09-08     Completed Date:  1999-09-08     Revised Date:  2013-09-26    
Medline Journal Info:
Nlm Unique ID:  8502536     Medline TA:  J Appl Physiol (1985)     Country:  UNITED STATES    
Other Details:
Languages:  eng     Pagination:  843-52     Citation Subset:  IM; S    
Center for Activity and Ageing, School of Kinesiology, Faculty of Health Sciences, The University of Western Ontario, London, Ontario, Canada N6A 3K7.
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MeSH Terms
Action Potentials / physiology
Age Factors
Electric Stimulation
Motor Neurons / physiology*
Muscle Contraction / physiology*
Muscle Fibers, Fast-Twitch / physiology
Muscle, Skeletal / physiology*

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