Activation varies among the knee extensor muscles during a submaximal fatiguing contraction in the seated and supine postures

• Published in: Journal of applied physiology (1985) 2003-10, Vol.95 (4), p.1515-1522
• Main Authors: Rochette, L, Hunter, S. K, Place, N, Lepers, R
• Format: Article
• Language: English
• Subjects: Adult; Biological and medical sciences; Electromyography; Fatigue; Fundamental and applied biological sciences. Psychology; Humans; Isometric Contraction - physiology; Knee; Knee - physiology; Male; Muscle Contraction - physiology; Muscle Fatigue - physiology; Muscle, Skeletal - physiology; Muscular system; Posture - physiology; Supine Position; Torque
• ISSN: 8750-7587; 1522-1601
• DOI: 10.1152/japplphysiol.00334.2003

1 Institut National de la Santé et de la Recherche Médicale/Equipe de Recherche et d'Innovation Technologique 0207, Motricité-Plasticité, Unité de Formation et de Recherche Sciences et Techniques des Activités Physiques et Sportive, Université de Bourgogne, 21078 Dijon, France; and 2 Department of Integrative Physiology University of Colorado at Boulder, Boulder, Colorado 80309-0354 Submitted 3 April 2003 ; accepted in final form 27 June 2003 Ten young men sustained an isometric contraction of the knee extensor muscles at 20% of the maximum voluntary contraction (MVC) torque on three separate occasions in a seated posture. Subjects performed an isometric knee extension contraction on a fourth occasion in a supine posture. The time to task failure for the seated posture was similar across sessions (291 ± 84 s; P > 0.05), and the MVC torque was similarly reduced across sessions after the fatiguing contraction (42 ± 12%). The rate of increase in electromyograph (EMG) activity (%MVC) and torque fluctuations during the fatiguing contractions were similar across sessions. However, the rate of increase in EMG differed among the knee extensor muscles: the rectus femoris began at a greater amplitude (31.5 ± 11.0%) compared with the vastus lateralis and vastus medialis muscles (18.8 ± 5.3%), but it ended at a similar value (45.4 ± 3.1%). The time to task failure and increase in EMG activity were similar for the seated and supine tasks; however, the reduction in MVC torque was greater for the seated posture. These findings indicate that the time to task failure for the knee extensor muscles that have a common tendon insertion did not alter over repeat sessions as had been observed for the elbow flexor muscles (Hunter SK and Enoka RM. J Appl Physiol 94: 108-118, 2003). electromyograph; force fluctuations; task failure; muscle length Address for reprint requests and other correspondence: L. Rochette, Institut National de la Santé et de la Recherche Médicale/Equipe de Recherche et d'Innovation Technologique 0207, Unité de formation et de Recherche Sciences et Techniques des Activités Physiques et Sportive, Universite de Bourgogne, 21078 Dijon, France.