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Effects of submaximal activation on the determinants of power of chemically skinned rat soleus fibres

Gilliver, Sally F and Degens, Hans and Jones, David A and Rittweger, Joern (2011) Effects of submaximal activation on the determinants of power of chemically skinned rat soleus fibres. Experimental Physiology, 96 (2), pp. 171-178. ISSN 0958-0670.

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Abstract

Reducing the activating calcium concentration with skinned fibres is known to decrease isometric force and maximal shortening velocity, both of which will reduce the peak power. However, power is also a function of the curvature of the force-velocity relationship, and there is limited information on how changes in activating calcium affect this important property of muscle fibres. Force-velocity relationships of permeabilized single type I fibres from rat soleus muscle were determined using isotonic contractions at 15°C with both maximal (pCa 4.5) and submaximal activation (pCa 5.6). The rate of tension redevelopment (k(tr)), which provides a measure of sum of the apparent rate constants for cross-bridge attachment and detachment (f(app) + g(app)) following a rapid release and restretch, was also measured. Compared with pCa 4.5, specific tension (P(o)) at pCa 5.6 declined by 22 ± 8% (mean ± s.d.) and the maximal velocity of shortening (V(max)) fell by 44 ± 7%, but curvature of the force-velocity relationship (a/P(o)) rose by 47 ± 31%, indicating a less concave relationship. The value of k(tr) declined by 23 ± 7%. The change in a/P(o) reduced the impact of changes in P(o) and V(max) on peak power by approximately 25%. Fitting the data to Huxley's model of cross-bridge action suggests that lower activating calcium decreased both the rate constant for cross-bridge attachment (f) and that for detachment of negatively strained cross-bridges (g(2)). The fact that V(max) (and thus g(2)) changed to a greater extent than k(tr) (f(app) + g(app)) is the reason that reduced activation results in a reduction in curvature of the force-velocity relationship.

Document Type:Article
Title:Effects of submaximal activation on the determinants of power of chemically skinned rat soleus fibres
Authors:
AuthorsInstitution or Email of Authors
Gilliver, Sally FManchester Metropolitan University
Degens, HansManchester Metropolitan University
Jones, David AManchester Metropolitan University
Rittweger, Joernjoern.rittweger@dlr.de
Date:February 2011
Journal or Publication Title:Experimental Physiology
Refereed publication:Yes
In SCOPUS:Yes
In ISI Web of Science:Yes
Volume:96
Page Range:pp. 171-178
ISSN:0958-0670
Status:Published
Keywords:Skeletal muscle; skinned fibres; power; force-velocity relationship
HGF - Research field:Aeronautics, Space and Transport (old)
HGF - Program:Space (old)
HGF - Program Themes:W FR - Forschung unter Weltraumbedingungen (old)
DLR - Research area:Space
DLR - Program:W FR - Forschung unter Weltraumbedingungen
DLR - Research theme (Project):W - Vorhaben Integrative Studien (old)
Location: Köln-Porz
Institutes and Institutions:Institute of Aerospace Medicine > Space Physiology
Deposited By: Jörn Rittweger
Deposited On:09 Feb 2011 10:39
Last Modified:12 Dec 2013 21:14

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