The mechanics of mouse skeletal muscle when shortening during relaxation

Barclay, CJ and Lichtwark, GA (2007) The mechanics of mouse skeletal muscle when shortening during relaxation. Journal of Biomechanics, 40 14: 3121-3129. doi:10.1016/j.jbiomech.2007.03.024


Author Barclay, CJ
Lichtwark, GA
Title The mechanics of mouse skeletal muscle when shortening during relaxation
Journal name Journal of Biomechanics   Check publisher's open access policy
ISSN 0021-9290
Publication date 2007-01-01
Sub-type Article (original research)
DOI 10.1016/j.jbiomech.2007.03.024
Volume 40
Issue 14
Start page 3121
End page 3129
Total pages 9
Editor Guilak , Farshid
Place of publication Oxford , U.K.
Publisher Permagon
Language eng
Subject 1106 Human Movement and Sports Science
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 °C) 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 not, vert, similar50% 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.
Keyword skeletal muscle mechanics
force-velocity
relaxation
fibre types
series elastic component
ISOMETRIC RELAXATION
STRIATED-MUSCLE
MUSCULAR FORCE
POWER OUTPUT
FIBERS
FROG
CONTRACTION
LOCOMOTION
PATTERNS
ACTIVATION
Q-Index Code C1

Document type: Journal Article
Sub-type: Article (original research)
Collection: School of Human Movement and Nutrition Sciences Publications
 
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Created: Tue, 15 Jun 2010, 22:00:16 EST