Clinical biomechanic correlates of cervical dysfunction: Part 4. Altered regional motor behavior

The present study examined organizational patterns of individual muscular contributions to head and neck motion. Previous studies of asymptomatic subjects with cervical motor asymmetry identified significant kinematic and myoelectric alterations. The current study evaluated 34 asymptomatic subjects categorized as to symmetry group based on initial palpatory test comparing regional motion responses of the head and neck to sidebending right and left. Electromyographic techniques were used to study muscular activity, indicating contraction frequency for each muscle monitored during active and passive test motions. Subjects with diagnosed regional motion asymmetry exhibited a significantly altered organization of electrically active and electrically silent muscles. Their pattern of muscle contraction was compromised just as frequently in the passive as in the active phases of motion. A positive sign of motion asymmetry on physical examination of the cervical region alerts the physician early to the presence of significant dysfunction in motor organization for efficient head/neck movement. The adaptive motor patterning in dysfunction can occur before the appearance of subjective pain.