Chronic trauma-induced neck pain impairs the neural control of the deep semispinalis cervicis muscle

Objective: The deep cervical extensors show structural changes in patients with neck pain however their activation has never been investigated in patients. This study is the first to present neurophysiological data from the deep semispinalis cervicis muscle in patients. Methods: Ten women with chronic neck pain and 10 healthy controls participated. Activity of the semispinalis cervicis was measured as subjects performed isometric contractions at 15 and 30 N force with continuous change in force direction in the range 0-360 degrees. Tuning curves of the EMG amplitude (average rectified value, ARV) were computed and the mean point of the ARV curves defined a directional vector, which determined the directional specificity of the muscle activity. Results: Patients displayed reduced directional specificity of the semispinalis cervicis (P < 0.05). Furthermore, the EMG amplitude during the circular contraction was lower for the patients (86.3 +/- 38.0 and 104.4 +/- 47.0 mu V for 15 and 30 N, respectively) compared to controls (226.4 +/- 128.5 and 315.8 +/- 205.5 mu V; P < 0.05). Conclusions: The activity of the semispinalis cervicis muscle is reduced and less defined in patients with neck pain confirming a disturbance in the neural control of this muscle. Significance: This finding suggests that exercises that target the deep semispinalis cervicis muscle may be relevant to include in the management of patients with neck pain. (C) 2011 International Federation of Clinical Neurophysiology. Published by Elsevier Ireland Ltd. All rights reserved.