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| Research article summary (published 5 Mar 2002): |
EMG activity and voluntary activation during knee-extensor concentric torque generation.
Full Abstract
This study was designed to re-examine and compare the neural drive of the knee extensors during isokinetic concentric muscular actions by means of the twitch interpolation technique (activation level, AL) and surface electromyographic (EMG) recordings (root mean square, RMS). Torque, AL and RMS amplitudes of three knee extensors and one knee flexor were measured in nine subjects during maximal and sub-maximal voluntary contractions, performed under concentric (60 degrees.s(-1) and 120 degrees.s(-1); Con60 and Con120, respectively) and isometric (Iso) conditions. Mean (SD) maximal voluntary torque was significantly lower ( P<0.01) during concentric contractions [Con60:
208.6 (26.8) Nm and Con120:
184.7 (26.4) Nm] compared with isometric contractions [327.4 (52.0) Nm]. A significantly lower AL ( P<0.05) was recorded during Con60 [80.9 (8.8)%] compared with Iso [87.9 (5.1)%] and Con120 [88.2 (6.6)%] maximal contractions. Simultaneously, a lower knee extensor average RMS amplitudes (av.RMS) was measured during Con60 maximal contractions compared with Iso and Con120 maximal contractions. The antagonist biceps femoris RMS values were not different between maximal Iso, Con60 and Con120 contractions. During sub-maximal voluntary contractions, the RMS/torque relationships were similar whatever the muscle considered (vastus lateralis, vastus medialis or rectus femoris) and the AL/av.RMS relationships did not reveal any noticeable differences between each contractile condition. The results of the present study indicate that av.RMS and AL describe similarly the neural drive during maximal and sub-maximal efforts and indicate that during maximal voluntary efforts, neural drive is dependent upon concentric angular velocity (up to 120 degrees.s(-1)). Thus, our results suggest that when applying different contractile conditions, the torque output is regulated via complex interactions between intrinsic muscular properties and the neural drive.
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Author information
Author/s: Babault, Nicolas (N); Pousson, Michel (M); Michaut, Anne (A); Ballay, Yves (Y); Hoecke, Jacques Van (JV);
Affiliation: Groupe Analyse du Mouvement (GAM), Faculté des Sciences du Sport, Université de Bourgogne, BP 27877, 21078 Dijon Cedex, France. nicolas.babault@u-bourgogne.fr
Journal and publication information
Publication Type: Journal Article
Journal: European journal of applied physiology (Eur J Appl Physiol), published in Germany. (Language: eng)
Reference: 2002-Apr; vol 86 (issue 6) : pp 541-7
Dates: Created 2002/04/10; Completed 2002/10/29; Revised 2004/11/17;
PMID: 11944103, status: MEDLINE (last retrieval date: 11/6/2008)
Sourced from the National Library of Medicine. Abstract text and other information may be subject to copyright.
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