Electromyographic Activity of Sternocleidomastoid Muscle in Individuals With Neck Pain and Healthy Volunteers: A Reliability and Between-Group Differences Examination.

Objectives: The purpose of this study was to evaluate the electromyographic activity of the sternocleidomastoid muscle during the performance of the craniocervical flexion test (CCFT) in individuals with neck pain and healthy volunteers, assess the reliability of this method, and examine possible between-population differences.

Methods: Electromyographic activity of the sternocleidomastoid muscles of 22 individuals with neck pain and 22 healthy participants was recorded during the 55 stages of the CCFT. Pain (visual analog scale) and disability (Neck Disability Index) levels and pain duration were recorded for the participants with neck pain. Reliability of electromyography was evaluated with the intraclass correlation coefficient, standard error of measurement, and minimum detectable change.

Results: Within-day reliability indices of electromyographic activity were very good to excellent (intraclass correlation coefficients, 0.86-0.98; standard error of measurement, 1.8%-7.6%; minimum detectable change, 5.0%-21.1%). For the head-lift normalization method, 2-way analysis of variance revealed significant between-group differences (P < .02); however, these were not clinically significant when reliability test-retest error was considered. Differences between contraction levels were significant (P < .001); however, the group by contraction level interaction factor was nonsignificant. Therefore, the between-groups electromyographic increases noted with increasing contraction levels were similar. No correlation was identified between participants' electromyography data and pain or disability.

Conclusion: In participants with moderate pain, disability, and pain duration, no clear alterations in electromyographic activity of the sternocleidomastoid could be detected with the CCFT. Reliability of the test used was very good.