Increased neck muscle activity and impaired balance among females with whiplash-related chronic neck pain: a cross-sectional study.

This study  examines neck muscle activity and postural control in patients with whiplash-associated disorder compared with healthy controls.The subjects were ten females with whiplash-associated disorder and 10 healthy female controls.  Surface electromyography measured muscle activity of the anterior scalene, sternocleidomastoid, neck extensors and upper trapezius muscles, expressed as mean relative activity related to maximum voluntary electromyography (%MVE). On a force plate, 3 balance tasks (Romberg stance with open and closed eyes, 1-legged stance) and a perturbation task with sudden unloading, were performed. The total area, areas from slow and fast components, and range of displacements were calculated from decomposed centre of pressure anterior-posterior and medial-lateral signals.  While performing balance tasks with closed eyes and one-legged stance, the relative mean activity of all 4 muscles was substantially increased in whiplash-associated disorder compared with healthy controls. Postural sway was also significantly increased.

The researchers found that increased neck muscle activity and increased postural sway during simple balance tasks suggest disturbed sensory feedback patterns in people with whiplash-associated disorder, which may have detrimental effects when performing daily activities.