Document Detail

Activity of motor units during concentric and eccentric contractions.
MedLine Citation:
PMID:  3324772     Owner:  NLM     Status:  MEDLINE    
Motor unit activity was investigated in the biceps brachii of twelve men during concentric (CC) and eccentric (EC) contractions by means of computer aided intramuscular spike amplitude-frequency (ISAF) histograms and surface EMG frequency power spectral analyses. Simultaneous recordings of the intramuscular and surface EMG signals were made during both types of contractions with the elbow joint angle varying from 30 to 150 degrees in reference to a fully extended position. Results demonstrated that r.m.s. amplitude and mean power frequency of the surface EMG were significantly higher during CC, particularly at shorter muscle length; e.g., 259 vs. 131 microV (p less than 0.01) and 102 vs. 91 Hz (p less than 0.05). The intramuscular spike recordings made at 45, 90 and 135 degrees showed greater motor unit (MU) activities during CC along with the presence of MUs with relatively large spike amplitude. The pooled data on the ISAF histograms revealed significantly greater mean MU spike amplitude and frequency during CC as compared to EC; e.g., 439 vs. 108 microV and 16.1 vs. 13.0 Hz at 135 degrees, respectively. These data suggest that EC is associated with much less pronounced MU recruitment and rate modulation due to economical tension development which might be a result of better utilization of elastic energy, particularly those inherent in the actin-myosin cross bridges and also a favorable length-tension relationship under the present experimental conditions.
T Moritani; S Muramatsu; M Muro
Publication Detail:
Type:  Journal Article; Research Support, Non-U.S. Gov't; Review    
Journal Detail:
Title:  American journal of physical medicine     Volume:  66     ISSN:  0002-9491     ISO Abbreviation:  Am J Phys Med     Publication Date:  1987 Dec 
Date Detail:
Created Date:  1988-03-10     Completed Date:  1988-03-10     Revised Date:  2006-11-15    
Medline Journal Info:
Nlm Unique ID:  0370503     Medline TA:  Am J Phys Med     Country:  UNITED STATES    
Other Details:
Languages:  eng     Pagination:  338-50     Citation Subset:  AIM; IM    
Human Performance Laboratory, Kyoto University, Japan.
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MeSH Terms
Muscle Contraction*

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

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