Association between neck muscle coactivation, pain, and strength in women with neck pain.

This study investigates the relationship between neck muscle coactivation, neck strength and perceived pain and disability in women with neck pain. Surface electromyography (EMG) was acquired from the sternocleidomastoid (SCM) and splenius capitis (SC) muscles of 13 women with chronic neck pain and 10 controls as they performed 1) maximal voluntary contractions (MVC) in flexion, extension and left and right lateral flexion, 2) ramped contractions from 0% to 50% MVC in flexion and extension and 3) circular contractions in the horizontal plane at 15N and 30N force. Higher values of EMG amplitude were observed for the SC (antagonist) during ramped neck flexion and for the SCM during ramped extension in the patient group (P<0.05). The patients displayed reduced values of directional specificity in the surface EMG of the SCM and SC for the circular contractions (P<0.05). The EMG amplitude of SC during cervical flexion was positively correlated with the patients' pain (R² =0.35, P<0.05) and perceived disability (R² 0.53, P<0.01). An inverse correlation was evident between the amount of activation of SC during cervical flexion and strength (R² =0.54, P<0.01). These observations indicate a relationship between alterations in neuromuscular control in patients with neck pain and functional consequences, including impaired motor performance and increased levels of perceived disability.