Experimental muscle pain results in reorganization of coordination among trapezius muscle subdivisions during repetitive shoulder flexion

• Published in: Experimental brain research Vol. 178; no. 3; pp. 385 - 393
• Main Authors: Falla, Deborah, Farina, Dario, Graven-Nielsen, Thomas
• Format: Journal Article
• Language: English
• Published: Berlin Springer 01.04.2007; Springer Nature B.V
• Subjects: Adaptation, Physiological - physiology; Adult; Afferent Pathways - physiology; Biological and medical sciences; Cranial nerves. Spinal roots. Peripheral nerves. Autonomic nervous system. Gustation. Olfaction; Elbow; Electrodes; Electromyography; Feedback - physiology; Female; Functional Laterality - physiology; Fundamental and applied biological sciences. Psychology; Humans; Inflammation Mediators - adverse effects; Male; Medical sciences; Motor control and motor pathways. Reflexes. Control centers of vegetative functions. Vestibular system and equilibration; Motor Neurons - physiology; Muscle Contraction - physiology; Muscle Fibers, Skeletal - physiology; Muscle pain; Muscle, Skeletal - innervation; Muscle, Skeletal - physiopathology; Neck pain; Nervous system (semeiology, syndromes); Neural Conduction - physiology; Neurology; Neuromuscular Junction - physiology; Neurons, Afferent - physiology; Nociceptors - physiology; Reaction Time - physiology; Saline Solution, Hypertonic - adverse effects; Shoulder - physiology; Shoulder Pain - physiopathology; Vertebrates: nervous system and sense organs; Italy; Human; Muscle fiber conduction velocity, Dynamic contraction, Electromyography; Electrophysiology; Experimental pain; Muscular fiber; Muscle contraction; Muscular coordination; Trapezius muscle; Pain; Shoulder; Body movement; Electromyography; Upper limb
• ISSN: 0014-4819; 1432-1106
• DOI: 10.1007/s00221-006-0746-6

The aim of the study was to examine the effect of experimental unilateral upper trapezius muscle pain on the relative activation of trapezius muscle subdivisions bilaterally during repetitive movement of the upper limb. Surface EMG signals were detected from nine healthy subjects from the upper, middle and lower divisions of trapezius during a repetitive bilateral shoulder flexion task. Measurements were performed before and after injection of 0.5 ml hypertonic (pain condition) and isotonic (control) saline into the upper division of the right trapezius muscle in two experimental sessions. On the painful side, upper trapezius showed decreased EMG amplitude (average rectified value, ARV) and lower trapezius increased ARV throughout the entire task following the injection of hypertonic saline (40.0 +/- 22.2 vs. 26.0 +/- 17.4 microV, and 12.5 +/- 7.6 vs. 25.6 +/- 14.8 microV, respectively, at the beginning of the contraction). On the side contralateral to pain, greater estimates of ARV were identified for the upper division of trapezius as the task progressed (37.4 +/- 20.2 vs. 52.7 +/- 28.4 microV, at the end of the contraction). Muscle fiber conduction velocity did not change with pain in all three divisions of the right trapezius muscle. The results suggest that local elicitation of nociceptive afferents in the upper division of the trapezius induces reorganization in the coordinated activity of the three subdivisions of the trapezius in repetitive dynamic tasks.