The mechanics of mouse skeletal muscle when shortening during relaxation

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Title The mechanics of mouse skeletal muscle when shortening during relaxation
Author Barclay, Christopher John; Lichtwark, Glen Anthony
Journal Name Journal of Biomechanics
Year Published 2007
Place of publication Oxford
Publisher Elsevier
Abstract The dynamic properties of relaxing skeletal muscle have not been well characterised but are important for understanding muscle function during terrestrial locomotion, during which a considerable fraction of muscle work output can be produced during relaxation. The purpose of this study was to characterise the force–velocity properties of mouse skeletal muscle during relaxation. Experiments were performed in vitro (21 1C) using bundles of fibres from mouse soleus and EDL muscles. Isovelocity shortening was applied to muscles during relaxation following short tetanic contractions. Using data from different contractions with different shortening velocities, curves relating force output to shortening velocity were constructed at intervals during relaxation. The velocity component included contributions from shortening of both series elastic component (SEC) and contractile component (CC) because force output was not constant. Early in relaxation force–velocity relationships were linear but became progressively more curved as relaxation progressed. Force–velocity curves late in relaxation had the same curvature as those for the CC in fully activated muscles but Vmax was reduced to %50 of the value in fully activated muscles. These results were the same for slow- and fast-twitch muscles and for relaxation following maximal tetani and brief, sub-maximal tetani. The measured series elastic compliance was used to partition shortening velocity between SEC and CC. The curvature of the CC force–velocity relationship was constant during relaxation. The SEC accounted for most of the shortening and work output during relaxation and its power output during relaxation exceeded the maximum CC power output. It is proposed that unloading the CC, without any change in its overall length, accelerated cross-bridge detachment when shortening was applied during relaxation.
Peer Reviewed Yes
Published Yes
Alternative URI
Volume 40
Page from 3121
Page to 3129
ISSN 0021-9290
Date Accessioned 2007-10-24
Date Available 2015-05-11T05:39:10Z
Language en_US
Research Centre Menzies Health Institute Qld
Faculty Griffith Health Faculty
Subject PRE2009-Animal Physiology-Cell
Publication Type Journal Articles (Refereed Article)
Publication Type Code c1

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