HOME HELP FEEDBACK SUBSCRIPTIONS ARCHIVE SEARCH TABLE OF CONTENTS		QUICK SEARCH:   [advanced] Author: Keyword(s): Year:  Vol:  Page:

This Article Full Text Full Text (PDF) All Versions of this Article: 576/3/913    most recent jphysiol.2006.116343v1 Services Email this article to a friend Similar articles in this journal Similar articles in PubMed Alert me to new issues of the journal Download to citation manager Citing Articles Citing Articles via HighWire Citing Articles via Google Scholar Google Scholar Articles by Jones, D. A. Articles by de Haan, A. Search for Related Content PubMed PubMed Citation Articles by Jones, D. A. Articles by de Haan, A. Related Collections Skeletal Muscle and Exercise

¹ Institute for Biophysical and Clinical Research into Human Movement, Manchester Metropolitan University, Hassall Road, Alsager, Cheshire, ST7 2HL, UK
² Faculty of Human Movement Sciences, Vrije Universiteit, Van der Boechorststraat 9, 1081 BT Amsterdam, The Netherlands
³ School of Sport and Exercise Sciences, University of Birmingham, Birmingham B15 2TT, UK

Slow relaxation from an isometric contraction is characteristic of acutely fatigued muscle and is associated with a decrease in the maximum velocity of unloaded shortening (V_max) and both these phenomena might be due to a decreased rate of cross bridge detachment. We have compared the change in relaxation rate with that of various parameters of the force–velocity relationship over the course of an ischaemic series of fatiguing contractions and subsequent recovery using the human adductor pollicis muscle working in vivo at approximately 37°C in nine healthy young subjects. Maximal isometric force (F₀) decreased from 91.0 ± 1.9 to 58.3 ± 3.5 N (mean ± S.E.M.). Maximum power decreased from 53.6 ± 4.0 to 17.7 ± 1.2 (arbitrary units) while relaxation rate declined from –10.3 ± 0.38 to –2.56 ± 0.29 s^–1. V_max showed a smaller relative change from 673 ± 20 to 560 ± 46 deg s^–1 and with a time course that differed markedly from that of slowing of relaxation, showing very little change until late in the series of contractions. Curvature of the force–velocity relationship increased (a/F₀ decreasing from 0.22 ± 0.02 to 0.11 ± 0.02) with fatigue and with a time course that was similar to that of the loss of power and the slowing of relaxation. It is concluded that for human muscle working at a normal physiological temperature the change in curvature of the force–velocity relationship with fatigue is a major cause of loss of power and may share a common underlying mechanism with the slowing of relaxation from an isometric contraction.

(Received 1 July 2006; accepted after revision 15 August 2006; first published online 17 August 2006)
Corresponding author D. A. Jones: School of Sport and Exercise Sciences, University of Birmingham, Birmingham B15 2TT, UK. Email: d.a.jones{at}bham.ac.uk

This article has been cited by other articles:

				R. H. Fitts The cross-bridge cycle and skeletal muscle fatigue J Appl Physiol, February 1, 2008; 104(2): 551 - 558. [Abstract] [Full Text] [PDF]

				D. G. Allen, G. D. Lamb, and H. Westerblad Skeletal Muscle Fatigue: Cellular Mechanisms Physiol Rev, January 1, 2008; 88(1): 287 - 332. [Abstract] [Full Text] [PDF]

				D. G. Allen, G. D. Lamb, and H. Westerblad Impaired calcium release during fatigue J Appl Physiol, January 1, 2008; 104(1): 296 - 305. [Abstract] [Full Text] [PDF]