Document Detail

Effects of low-frequency stimulation on the tension-frequency relations of fast-twitch motor units in the cat.
MedLine Citation:
PMID:  1753294     Owner:  NLM     Status:  MEDLINE    
1. Tension-frequency relations were measured in single fast-twitch motor units of the cat flexor digitorum longus (FDL) muscle before and after stimulating each unit with a series of 10-s trains at 20 Hz. The 20-Hz conditioning stimulation produced a combination of potentiating and fatiguing effects, similar to those previously reported to follow higher frequency stimulation of single motor units of the cat and maximal voluntary contractions in man. 2. The conditioning stimulation left three types of after effects: 1) short-term potentiation, 2) a somewhat longer lasting depression of maximal tension, and 3) a delayed depression of low-frequency responses (low-frequency fatigue). 3. The immediate potentiating effect of the conditioning stimulation was most prominent in fatigue-resistant (FR) motor units, whereas depression of maximal tension and low-frequency fatigue were most prominent in fatigue-intermediate (FI) and highly fatigable (FF) motor units. 4. On the basis of our results and those of other investigators, we propose that potentiation, depression of maximal tension, and low-frequency fatigue are independent phenomena, acting at distinct points in the excitation-contraction coupling process. 5. Our results suggest that both potentiation and low-frequency fatigue can result from rather modest amounts of preceding activity. Thus large changes in muscle force production are not unique to maximal contractions but are likely to follow sustained, submaximal contractions as well.
R K Powers; M D Binder
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Publication Detail:
Type:  Journal Article; Research Support, U.S. Gov't, P.H.S.    
Journal Detail:
Title:  Journal of neurophysiology     Volume:  66     ISSN:  0022-3077     ISO Abbreviation:  J. Neurophysiol.     Publication Date:  1991 Sep 
Date Detail:
Created Date:  1992-01-30     Completed Date:  1992-01-30     Revised Date:  2007-11-14    
Medline Journal Info:
Nlm Unique ID:  0375404     Medline TA:  J Neurophysiol     Country:  UNITED STATES    
Other Details:
Languages:  eng     Pagination:  905-18     Citation Subset:  IM    
Department of Physiology and Biophysics, University of Washington School of Medicine, Seattle 98195.
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MeSH Terms
Electric Stimulation
Electrodes, Implanted
Motor Neurons / physiology*
Muscle Contraction / physiology
Muscles / innervation,  physiology*
Grant Support

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