Trunk muscle coordination in reaction to load-release in a position without vertical postural demand

• Published in: Experimental brain research Vol. 185; no. 3; pp. 383 - 390
• Main Authors: Eriksson Crommert, A. E. Martin, Thorstensson, Alf
• Format: Journal Article
• Language: English
• Published: Berlin/Heidelberg Springer-Verlag 01.03.2008; Springer; Springer Nature B.V
• Subjects: Abdominal Muscles - physiology; Adult; Biological and medical sciences; Biomedical and Life Sciences; Biomedicine; Disorders of higher nervous function. Focal brain diseases. Central vestibular syndrome and deafness. Brain stem syndromes; Electromyography - methods; Fundamental and applied biological sciences. Psychology; Humans; Male; Medical sciences; MEDICIN; Medicin och hälsovetenskap; MEDICINE; Motor control and motor pathways. Reflexes. Control centers of vegetative functions. Vestibular system and equilibration; Muscle Contraction - physiology; Muscle, Skeletal - physiology; Nervous system (semeiology, syndromes); Neurology; Neurosciences; Postural Balance - physiology; Posture - physiology; Psychomotor Performance - physiology; Research Article; Vertebrates: nervous system and sense organs; Weight-Bearing - physiology; Spine control; Electromyography; Abdominal muscles; Human; Load; Force; Electrophysiology; Lower limb; Segmental movement; Synergism; Muscular coordination; Posture; Segmental; Muscle; Timing; Release
• ISSN: 0014-4819; 1432-1106; 1432-1106
• DOI: 10.1007/s00221-007-1159-x

The aim of this study was to investigate the coordination between the innermost muscle layer of the ventro-lateral abdominal wall, the transversus abdominis (TrA), and other trunk muscles, in reaction to a load-release without the postural demand of keeping the trunk upright. Eleven healthy male volunteers participated. Intramuscular fine-wire electromyography (EMG) was obtained bilaterally from the TrA, rectus abdominis (RA), obliquus externus (OE) and erector spinae (ES) muscles. The subjects lay on their right side on a horizontal swivel-table with immobilized pelvis and lower limbs and with the trunk strapped to a movable platform allowing for trunk flexion and extension. Subjects maintained trunk flexion or extension at different force levels against a static resistance, which was suddenly released. They were instructed to resume the start position as fast as possible. EMG signals were analysed with respect to amplitude and timing of muscle activation. Following released static flexion, TrA increased its activity in synergy with ES. Also in released static extension, TrA increased its activity, but now in synergy with RA and OE. The direction-independent activation of TrA indicates a role of this muscle in controlling inter-segmental movements of the lumbar spine. This function was not accompanied by an early activation of TrA as has been shown previously for trunk perturbations in standing, i.e. a situation with an additional demand of maintaining the trunk posture upright against gravity.