Document Detail

Why does knee extensor muscles torque decrease after eccentric-type exercise?
MedLine Citation:
PMID:  16355074     Owner:  NLM     Status:  MEDLINE    
AIM: The purpose of this study was to re-examine central and peripheral origins of neuromuscular fatigue after a highly strenuous eccentric exercise of the knee extensor muscles (KE) using both voluntary/evoked contractions and electromyographic recordings (EMG). METHODS: Before, and 30 min after 15 min of intermittent one-logged downhill running, maximal percutaneous electrical stimulations (single twitch, 0.5 s tetanus at 20 Hz and 80 Hz) were applied to the femoral nerve of 10 male subjects. Electrically evoked superimposed twitches were delivered during isometric maximal voluntary contraction (MVC) to determine maximal voluntary activation (%VA). Vastus lateralis (VL), vastus medialis (VM) and biceps femoris (BF) EMG were recorded during MVC and quantified using the root mean square (RMS) value. M-wave characteristics were also determined. RESULTS: KE MVC and %VA decreased significantly with fatigue (-19.6+/-6.1%; P<0.001 and -7.8+/-6.6%; P<0.01, respectively). Peak tetanus tension at 20 and 80 Hz (P20 and P80, respectively) declined (P<0.001), concurrently with a decrement of the P20 x P80(-1) ratio (-37.3+/-16.6%; P<0.001). Antagonist muscle coactivation, RMS to M-wave peak-to-peak amplitude and MVC x P80(-1) ratios were unchanged after the fatiguing exercise. CONCLUSIONS: The results reveal that part of the large loss in MVC may have a central origin but most of the MVC decrement is due to the presence of low-frequency fatigue while possible contractile failure cannot be excluded.
V Martin; G Y Millet; G Lattier; L Perrod
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Publication Detail:
Type:  Journal Article; Research Support, Non-U.S. Gov't    
Journal Detail:
Title:  The Journal of sports medicine and physical fitness     Volume:  45     ISSN:  0022-4707     ISO Abbreviation:  -     Publication Date:  2005 Jun 
Date Detail:
Created Date:  2005-12-15     Completed Date:  2006-01-26     Revised Date:  2006-11-15    
Medline Journal Info:
Nlm Unique ID:  0376337     Medline TA:  J Sports Med Phys Fitness     Country:  Italy    
Other Details:
Languages:  eng     Pagination:  143-51     Citation Subset:  IM    
INSERM/ERIT-M 0207 Motricité-Plasticité Faculté des Sciences du Sport, Université de Bourgogne, Dijon, France.
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MeSH Terms
Electric Stimulation
Exercise / physiology
Femoral Nerve / physiology
Knee / physiology*
Lactic Acid / blood
Muscle Contraction / physiology*
Muscle Fatigue / physiology*
Muscle, Skeletal / physiology*
Running / physiology
Reg. No./Substance:
50-21-5/Lactic Acid

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

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