Physiological alterations of maximal voluntary quadriceps activation by changes of knee joint angle

• Published in: Muscle & nerve Vol. 24; no. 5; pp. 667 - 672
• Main Authors: Becker, Roland, Awiszus, Friedemann
• Format: Journal Article
• Language: English
• Published: New York John Wiley & Sons, Inc 01.05.2001; Wiley
• Subjects: Adult; Biological and medical sciences; Fundamental and applied biological sciences. Psychology; Humans; Isometric Contraction - physiology; Knee Joint - physiology; knee joint angle; Male; Motor control and motor pathways. Reflexes. Control centers of vegetative functions. Vestibular system and equilibration; Muscle Contraction - physiology; Muscle, Skeletal - physiology; quadriceps muscle; twitch-interpolation technique; Vertebrates: nervous system and sense organs; voluntary activation; Osteoarticular system; Knee; Human; Body movement; Lower limb; Quadriceps muscle; Joint; Voluntary movement; Muscle contraction; Motor control
• ISSN: 0148-639X; 1097-4598
• DOI: 10.1002/mus.1053

The purpose of this study was to investigate the influence of different angles of the knee joint on voluntary activation of the quadriceps muscle, estimating the ability of a subject to activate a muscle maximally by means of voluntary contraction. Isometric torque measurement was performed on 6 healthy subjects in 5° intervals between 30° and 90° of knee joint flexion. Superimposed twitches at maximal voluntary contraction (MVC) and at a level of 60% and 40% of the MVC were applied and the voluntary activation estimated. At between 30° and 75° of knee flexion, the maximal extension torque increased at an average rate of 2.67 ± 0.6 Nm/degree, followed by a decline with further flexion. However, throughout the joint‐angle range tested, voluntary activation increased on average by 0.37%/degree with a maximum at 90° of flexion. Due to the influence of joint position it is not possible to generalize results obtained at the knee joint angle of 90° of flexion, which is usually used for the quadriceps twitch‐interpolation technique. Consequently, it is useful to investigate voluntary activation deficits in knee joint disorders at a range of knee joint angles that includes, in particular, the more extended joint angles used frequently during daily activity. © 2001 John Wiley & Sons, Inc. Muscle Nerve 24: 667–672, 2001