Myoelectric manifestations of sternocleidomastoid and anterior scalene muscle fatigue in chronic neck pain patients

• Published in: Clinical neurophysiology Vol. 114; no. 3; pp. 488 - 495
• Main Authors: Falla, D, Rainoldi, A, Merletti, R, Jull, G
• Format: Journal Article
• Language: English
• Published: Shannon Elsevier Ireland Ltd 01.03.2003; Elsevier Science
• Subjects: Adolescent; Adult; Anterior scalenes; Biological and medical sciences; Chronic Disease; Diseases of the osteoarticular system; Diseases of the spine; Electromyography; Female; Humans; Male; Medical sciences; Middle Aged; Muscle fatigue; Muscle Fatigue - physiology; Neck Muscles - physiopathology; Neck pain; Neck Pain - diagnosis; Neck Pain - physiopathology; Sternocleidomastoid; Surface electromyography; VAS, visual analogue scale; CC, correlation coefficient; MVC, maximum voluntary contraction; ARV, average rectified value; Surface electromyography; SCM, sternocleidomastoid; NME, neuromuscular efficiency; MNF, mean spectral frequency; Anterior scalenes; MU, motor unit; Neck pain; Muscle fatigue; NMNF, normalised mean frequency; AS, anterior scalene; SD, standard deviation; CV, conduction velocity; NDI, neck disability index; Sternocleidomastoid; ICC, intraclass correlation coefficient; sEMG, surface electromyography; Human; Stemocleidomastoid; Pathophysiology; Diseases of the osteoarticular system; Fatigue; Spine disease; Scalenus muscle; Electrodiagnosis; Chronic; Pain; Sternocleidomastoid muscle; Electromyography; Cervical spine
• ISSN: 1388-2457; 1872-8952
• DOI: 10.1016/S1388-2457(02)00418-2

Objective: This study compares myoelectric manifestations of fatigue of the sternocleidomastoid (SCM) and anterior scalene (AS) muscles between 10 chronic neck pain subjects and 10 normal matched controls. Methods: Surface electromyography (sEMG) signals were recorded from the sternal head of SCM and AS muscles bilaterally during sub-maximal isometric cervical flexion contractions at 25 and 50% of the maximum voluntary contraction (MVC). The mean frequency, average rectified value and conduction velocity of the sEMG signal were calculated to quantify myoelectric manifestations of muscle fatigue. Results: For both the SCM and AS muscles, the Mann–Whitney U test indicated that the initial value and slope of the mean frequency in neck pain patients were greater than in healthy subjects ( P<0.05). This was significant both at 25 and 50% of MVC. Conclusions: These results suggest: (a) a predominance of type-II fibres in the neck pain patients and/or (b) greater fatigability of the superficial cervical flexors in neck pain patients. These results are in agreement with previous muscle biopsy studies in subjects with neck pain, which identified transformation of slow-twitch type-I fibres to fast-twitch type-IIB fibres, as well as the clinical observation of reduced endurance in the cervical flexors in neck pain patients.