Voluntary activation level and muscle fiber recruitment of human quadriceps during lengthening contractions

Beltman, J. G. M., Sargeant, A. J., van Mechelen, W. and de Haan, A. (2004) Voluntary activation level and muscle fiber recruitment of human quadriceps during lengthening contractions. Journal of Applied Physiology, 97 2: 619-626. doi:10.1152/japplphysiol.01202.2003


Author Beltman, J. G. M.
Sargeant, A. J.
van Mechelen, W.
de Haan, A.
Title Voluntary activation level and muscle fiber recruitment of human quadriceps during lengthening contractions
Journal name Journal of Applied Physiology   Check publisher's open access policy
ISSN 1522-1601
8750-7587
Publication date 2004-01-01
Sub-type Article (original research)
DOI 10.1152/japplphysiol.01202.2003
Open Access Status Not Open Access
Volume 97
Issue 2
Start page 619
End page 626
Total pages 8
Place of publication Bethesda, MD
Publisher American Physiological Society
Language eng
Subject 1106 Human Movement and Sports Science
Abstract Voluntary activation levels during lengthening, isometric, and shortening contractions (angular velocity 60°/s) were investigated by using electrical stimulation of the femoral nerve (triplet, 300 Hz) superimposed on maximal efforts. Recruitment of fiber populations was investigated by using the phosphocreatine-to-creatine ratio (PCr/Cr) of single characterized muscle fibers obtained from needle biopsies at rest and immediately after a series of 10 lengthening, isometric, and shortening contractions (1 s on/1 s off). Maximal voluntary torque was significantly higher during lengthening (270 ± 55 N·m) compared with shortening contractions (199 ± 47 N·m, P < 0.05) but was not different from isometric contractions (252 ± 47 N·m). Isometric torque was higher than torque during shortening (P < 0.05). Voluntary activation level during maximal attempted lengthening contractions (79 ± 8%) was significantly lower compared with isometric (93 ± 5%) and shortening contractions (92 ± 3%, P < 0.05). Mean PCr/Cr values of all fibers from all subjects at rest were 2.5 ± 0.6, 2.0 ± 0.7, and 2.0 ± 0.7, respectively, for type I, IIa, and IIax fibers. After 10 contractions, the mean PCr/Cr values for grouped fiber populations (regardless of fiber type) were all significantly different from rest (1.3 ± 0.2, 0.7 ± 0.3, and 0.8 ± 0.6 for lengthening, isometric, and shortening contractions, respectively; P < 0.05). The cumulative distributions of individual fiber populations after either contraction mode were significantly different from rest (P < 0.05). Curves after lengthening contractions were less shifted compared with curves from isometric and shortening contractions (P < 0.05), with a smaller shift for the type IIax compared with type I fibers in the lengthening contractions. The results indicate a reduced voluntary drive during lengthening contractions. PCr/Cr values of single fibers indicated a hierarchical order of recruitment of all fiber populations during maximal attempted lengthening contractions
Keyword isometric
phosphocreatine-to-creatine ratio
shortening
single fibers
Q-Index Code C1

Document type: Journal Article
Sub-type: Article (original research)
Collections: Excellence in Research Australia (ERA) - Collection
School of Human Movement and Nutrition Sciences Publications
 
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