Chronic neck pain and muscle activation characteristics of the shoulder complex.

Introduction: Neck pain is a very common musculoskeletal complaint in industrialized countries. Theoretically, chronic neck pain is thought to possibly change biomechanics and muscle activation patterns of the shoulder complex, causing its pain and dysfunction in the long term.
Purpose: The present cross-sectional study was conducted to compare shoulder complex muscle activation characteristics in patients with chronic non-specific neck pain, compared to healthy participants.
Method: Twenty patients with chronic neck pain and twenty healthy participants were recruited for the present study. Surface Electromyographic (sEMG) activity was recorded from four selected muscles (anterior and middle deltoid, upper and lower trapezius) during shoulder elevation with a predetermined load (25-30% of an individual's maximum voluntary exertion).
Result: Results revealed only two significant increased onset delays in the anterior and middle deltoid,and a peak delay in the upper trapezius in chronic neck pain patients. Furthermore, increased onset delay for other muscles and decreased peak normalized amplitude (MVE%) for all muscles were found in chronic neck pain patients; however, these findings were not statistically significant.
Conclusion: There were relationships between chronic non-specific neck pain and the shoulder muscle activation characteristic; hence, the alteration may be considered a predisposing factor for the shoulder dysfunction in future studies.
(Copyright © 2019. Published by Elsevier Ltd.)