Effectiveness of an 8-week exercise programme on pain and specificity of neck muscle activity in patients with chronic neck pain: a randomized controlled study

BACKGROUND: Although exercise can be effective for relief of neck pain, little is known about the effect of exercise on the neural control of neck muscles.

METHODS: A randomized controlled trial was conducted on 46 women with chronic neck pain to investigate the immediate effectiveness of an 8-week exercise programme on pain and directional specificity of neck muscle activity. At baseline, the patients completed questionnaires including the neck disability index (NDI) and performed a circular contraction of their head in the horizontal plane at 15 N force, with continuous change in force direction in the range 0-360°. Electromyography (EMG) was recorded from the sternocleidomastoid (SCM) and splenius capitis (SCap) muscles. Tuning curves of the EMG amplitude were computed, which depicts muscle activity over a range of force directions. The mean point of the tuning curves defined a directional vector, which determined the specificity of muscle activity. Patients were randomly assigned either to a training or control group.

RESULTS: A significant between-group difference in the change in NDI was observed. A reduction in NDI was observed following training (pre: 18.2 ± 7.4; post: 14.1 ± 6.5; p < 0.01) but not for the control group (pre: 17.5 ± 6.3; post: 16.6 ± 7.4). The training group showed higher specificity of muscle activity post-intervention (pre: 18.6 ± 9.8%, post: 24.7 ± 14.3%; p < 0.05), whereas no change occurred for the control group (pre: 19.4 ± 11.9%, post: 18.2 ± 10.1%).

CONCLUSION: An exercise programme that aims to enhance motor control of the cervical spine improves the specificity of neck muscle activity and reduces pain and disability in patients with neck pain.