title: Effects of vision and lumbar posture on trunk neuromuscular control.
abstract: The goal of this study was to determine the effects of vision and lumbar posture on trunk neuromuscular control. Torso perturbations were applied with a pushing device while the subjects were restrained at the pelvis in a kneeling-seated position. Torso kinematics and the muscle activity of the lumbar part of the M. Longissimus were recorded for 14 healthy subjects. Four conditions were included: a flexion, extension and neutral lumbar posture with eyes closed and the neutral posture with eyes open. Frequency response functions of the admittance and reflexes showed that there was no significant difference between the eyes open and eyes closed conditions, thereby confirming that vision does not play a role in the stabilization of the trunk during small-amplitude trunk perturbations. In contrast, manipulating posture did lead to significant differences. In particular, the flexed condition led to a lower admittance and lower reflex contribution compared to the neutral condition. Furthermore, the muscle pre-activation (prior to the onset of the perturbation) was significantly lower in the flexed posture compared to neutral. This confirms that flexing the lumbar spine increases the passive tissue stiffness and decreases the contribution of reflex activity to trunk control.
authors.affiliation: MOVE Research Institute Amsterdam, Faculty of Human Movement Science, VU University Amsterdam, van der Boechorststraat 9, 1081 BT Amsterdam, The Netherlands.
authors.forename: Erwin
authors.initials: E
authors.lastname: Maaswinkel
authors.affiliation: BioMechanical Engineering Department, Faculty of Mechanical Engineering, Delft University of Technology, Mekelweg 4, 2628 CD Delft, The Netherlands.
authors.forename: Paul
authors.initials: P
authors.lastname: van Drunen
authors.affiliation: MOVE Research Institute Amsterdam, Faculty of Human Movement Science, VU University Amsterdam, van der Boechorststraat 9, 1081 BT Amsterdam, The Netherlands.
authors.forename: Dirk-Jan H E J
authors.initials: DJ
authors.lastname: Veeger
authors.affiliation: MOVE Research Institute Amsterdam, Faculty of Human Movement Science, VU University Amsterdam, van der Boechorststraat 9, 1081 BT Amsterdam, The Netherlands. Electronic address: j.van.dieen@vu.nl.
authors.forename: Jaap H
authors.initials: JH
authors.lastname: van Dieën
mesh_terms: D000328:Adult; D001696:Biomechanical Phenomena; D004576:Electromyography; D005260:Female; D006801:Humans; D008159:Lumbar Vertebrae / Q000502:physiology*; D008297:Male; D009132:Muscles / Q000502:physiology*; D009424:Nervous System Physiological Phenomena; D011187:Posture / Q000502:physiology*; D012018:Reflex / Q000502:physiology; D060726:Torso / Q000502:physiology*; D014796:Visual Perception; D055815:Young Adult
keywords: Lumbar posture; System identification; Torso perturbations; Trunk neuromuscular control; Vision