Jaw Kinematics and Muscle Activation in Patients With Non-specific Chronic Neck Pain

Subjects will perform full-range cervical flexion, extension, side-bending and rotation actively in sitting position. In supine position, cervical flexion-rotation will be performed passively by the assessor.

A digital algometer with rubber head will be used to apply pressure on the muscles of subjects. When the subjects start to feel pain, the algometer will be removed immediately.

Subjects will stand in a relaxed position with colour markers on the earlobe and C7 spinous process. A photo of the head posture will be taken to calculate the included angle between the markers and the horizontal line.

Jaw kinematics is measured by Ultrasonic Jaw Motion Analyzer (Zebris). The subjects will perform jaw opening, closing, lateral left, lateral right and protrusion for three times.

Surface electromyography is used to assess the activities of bilateral masseter, anterior temporalis, sternocleidomastoid muscle and upper trapezius. Subjects will perform jaw resting and clenching.